CBSE Class 10

On this page, you will find Life Processes Class 10 Notes Science Chapter 6 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 6 Life Processes will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 6 Notes Life Processes

Life Processes Class 10 Notes Understanding the Lesson

1. Life Processes: All the processes like respiration, digestion, which together keep the living organisms alive and help in maintaining the functions of the body, are called life processes.

2. Nutrition: The process by which an organism obtains its food is called nutrition.
Modes of Nutrition:

• Autotrophic nutrition: Kind of nutrition in which inorganic materials like CO₂, water, etc. are utilised to prepare organic food by the process of photosynthesis. For example, green plants and some bacteria.
• Heterotrophic nutrition: Kind of nutrition in which organisms do not possess the ability to synthesise their own food. They depend on autotrophs for their food supply directly or indirectly. For example, animals, fungi.

3. Bio-catalysts: Enzymes are called bio-catalysts as they play an important role in chemical reactions taking place in living organisms.

4. Photosynthesis: Autotrophs take in CO₂ and H₂O and convert these into carbohydrates in the presence of chlorophyll and sunlight by the process called Photosynthesis.

5. Equation of Photosynthesis:

6. Raw Materials for Photosynthesis:

• Sunlight
• Chlorophyll-It helps to trap the energy of the Sun
• CO₂-It enters through Stomata
• Water-Water and dissolved minerals are taken up by the roots from soil

7. Products of Photosynthesis:

• Carbohydrates in the form of glucose
• Oxygen (O₂)-released as a by-product

8. Site of Photosynthesis:
Chloroplast is the site of photosynthesis. Chloroplast contains a green pigment called chlorophyll which helps to trap energy of sunlight.

9. Events of Photosynthesis:

• Absorption of light energy by chlorophyll.
• Conversion of light energy to chemical energy + splitting of water molecules into hydrogen and oxygen.
• Reduction of carbon dioxide to carbohydrates.

10. Structure of Leaf:
External structure of leaf comprises of

• Petiole: Stalk of leaf.
• Lamina: Flat, broad and expanded portion of leaf.
• Midrib: Midline which divides leaf into two equal halves.
• Veins: Supply water throughout surface of leaf.

11. Internal structure of leaf comprises of:

Epidermis: It has two parts:
(i) upper epidermis and
(ii) lower epidermis.

(i) Upper epidermis is usually covered by a waxy layer called cuticle which prevents water loss through transpiration.

(ii) Lower epidermis has stomata which help in gaseous exchange

Stomata: Tiny pores which are generally found in the lower epidermis and help in gaseous exchange and transpiration.

Guard cells: Bean-shaped cells which guard the opening of stomata. They have chloroplasts and have uneven thickening in their cell wall. Opening and closing of stomatal pore is done by guard cells. Movement of water into guard cells cause their swelling and open the stomatal pore. The shrinking of the guard cells when water moves out causes closing of stomatal pore.

12. Types of Heterotrophic Nutrition:

• Holozoic nutrition: The complex food material taken in by the organism is broken down into simpler and soluble molecules. For example, Human, Amoeba.
• Saprotrophic nutrition: The organisms feed on the dead and decaying matter. For example, Fungi.
• Parasitic nutrition: The organisms live either on or inside the organism to obtain its nutrition. For example, Lice, Cuscuta (amarbel).

13. Steps in Holozoic Nutrition:

• Ingestion
• Digestion
• Absorption
• Assimilation
• Egestion.

14. Nutrition in Amoeba
Temporary finger-like extensions of the cell surface called pseudopodia are used by Amoeba to engulf food. Pseudopodia fuse over the food particle forming a food vacuole in which complex substances are broken down into simpler ones and diffuse into the cytoplasm. The remaining undigested material moves to the surface of the cell and gets thrown out.

15. Nutrition in Paramoecium
In Paramoecium, food is moved to a specific spot by the movement of cilia which cover the entire surface of the cell.

16. Nutrition in Human Beings
Human digestive system consists of alimentary canal and the associated glands. The alimentary canal is a long tube extending from the mouth to the anus.

17. Mouth – Helps in intake of whole food.

18. Teeth – Helps in chewing and grinding of food.

19. Tongue – Helps in tasting food + rolling food + swallowing food.

20. Salivary glands – Secrete saliva and mucus. The enzyme called salivary amylase is present in saliva which breaks down the complex starch into sugar.

21. Oesophagus (food pipe) – Food moves towards stomach through oesophagus by rhythmic contraction of its muscles called peristaltic movements or peristalsis.

22. Stomach – Muscular walls of stomach help in mixing food thoroughly with digestive juices. Stomach has gastric glands which secrete gastric juice containing pepsin, hydrochloric acid and mucus.

• Pepsin helps in digestion of proteins.
• Hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin + kills germs present in food particles.
• Mucus protects the inner lining of the stomach from the action of the hydrochloric acid under normal conditions.

23. Small Intestine: A sphincter muscle regulates the exit of food from stomach into the highly coiled, longest part of the alimentary canal called the small intestine. Herbivores have a longer small intestine compared to the carnivores to allow the cellulose present in the grass to get digested. The digestive juices released in small intestine are:

(i) Bile juice: It is released from liver (stored in gall bladder). It helps to create alkaline medium in the small intestine for the pancreatic enzymes to act. Bile salts present in bile juice break down large fat globules into smaller globules (emulsification of fats) to increase the efficiency of enzyme action.

(ii) Pancreatic juice: It is released from pancreas and contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

(iii) Intestinal juice: The walls of the small intestine contain glands which secrete intestinal juice. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol. Intestinal juice completes the process of digestion.

(iv) Role of Villi: The digested food is absorbed by the inner lining or wall of the intestine with the help of villi. Villi are finger-like projections richly supplied with blood vessels and help to increase the surface area for absorption. Absorbed nutrients reach the cells through blood and are utilised for obtaining energy, building up new tissues and the repair of old tissues.

(v) Large Intestine: The unabsorbed food is sent into the large intestine where more villi absorb water from this material and remove the wastes through the anus by egestion. The exit of this waste material is regulated by the anal sphincter.

24. Respiration: The breakdown of simple food material to release energy is called as respiration. Aerobic respiration takes place in the presence of air (oxygen) whereas the anaerobic respiration occurs in the absence of air (oxygen). More amount of energy is released in aerobic respiration.

25. Glycolysis: This is the first step which occurs in the cytoplasm and results in breakdown of glucose (six-carbon molecule) into a three-carbon molecule called pyruvate. Glycolysis occurs both in aerobic as well as anaerobic respiration.

26. Fate of pyruvic acid (pyruvate):

• The pyruvate is converted into ethanol and carbon dioxide by the process called fermentation in yeast due to anaerobic respiration.
• The pyruvate is converted into a three-carbon compound lactic acid during respiration in muscle cells due to anaerobic respiration. Accumulation of lactic acid causes cramps in muscles.
• The pyruvate is broken down into carbon dioxide and water in presence of oxygen inside the mitochondria. The energy released during cellular respiration is used to synthesise a molecule called ATP which is used to fuel all other activities in the cell.

27. Types of Respiration:
(i) Aerobic

• Anaerobic respiration
• Aerobic respiration: It takes place in the presence air (oxygen).

Anaerobic respiration: It takes place in the absence of air (oxygen).
Respiration in plants: Respiration in plants is simpler than the respiration in animals.

28. Gaseous exchange occurs through:

• Stomata in leaves
• Lenticels in stems
• General surface of the roots.

29. Respiration in terrestrial animals: They use atmospheric oxygen for respiration.

30. Respiration in aquatic animals: Aquatic animals use the oxygen dissolved in water. They breathe at a faster rate since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air. Fishes take water from mouth and send it to the gills where the dissolved oxygen is taken up by blood.

31. Human Respiratory System: Air enters the body after getting filtered by fine hairs and mucus in the nostrils. The air then passes through trachea (present in throat) into the lungs. Rings of cartilage present on trachea prevent it from collapsing during the passage of air.

The trachea divide into bronchi which enter the lungs and divide further into bronchioles which finally terminate in balloon-like structures called alveoli which have a rich supply of blood vessels and help in exchange of gases.

32. Mechanism of breathing: During inhalation (breathing in), the volume of the chest cavity becomes larger as the ribs get lifted and diaphragm gets flattened. Air gets sucked into the lungs and fills the expanded alveoli. The blood brings carbon dioxide from the rest of the body to the alveoli and exchanges it for oxygen to be transported to all the cells in the body.

During exhalation (breathing out), the volume of the chest cavity becomes smaller as the ribs get relaxed and diaphragm moves upward (relaxes). Air rich in carbon dioxide gets pushed out of the lungs to come out through the nostrils.

33. Residual volume: It is the volume of air left behind in the lungs even after forceful breathing out of air. This helps to provide sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

34. Respiratory pigment: The respiratory pigment called haemoglobin in human beings is present in the red blood corpuscles. Haemoglobin has a very high affinity for oxygen.

35. Transportation
Transportation in Human Beings: Circulatory system helps to transport blood to various parts of the body to ensure the supply of nutrients and oxygen to these parts and remove carbon dioxide and metabolic wastes.
The circulatory system in human beings consists of:

• A pumping organ—a muscular heart
• Blood vessels—Arteries and veins
• Circulating medium—Blood and lymph

36. Steps in circulation of blood:

• The relaxed thin-walled upper chamber of the heart on the left, the left atrium, receives oxygen- rich blood from the lungs through the pulmonary vein.
• The left atrium contracts and transfers blood to the left ventricle.
• The left ventricle contracts and sends the oxygen-rich blood through aorta to the various parts of the body.
• De-oxygenated blood from the various parts of the body is transported by vena cava to the relaxed right upper chamber of the heart called the right atrium.
• The right atrium contracts and transfers blood to the right ventricle.
• The right ventricle pumps de-oxygenated blood for oxygenation to the lungs through pulmonary vein.
• Ventricles have thicker muscular walls than atrium as they have to pump blood into various organs.

37. Role of valves: Valves ensure that blood does not flow backwards when the atria or ventricles contract.

Significance of separation of right and left side of the heart: It is useful to prevent mixing of oxygenated and de-oxygenated blood. It also allows a highly efficient supply of oxygen to the body. It is useful for animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature.

38. Types of heart:
Fishes have a two chambered heart. Blood pumped by heart gets oxygenated by gills and passes directly to the rest of the body. This is called single circulation. Amphibians and reptiles have three- chambered hearts and tolerate some mixing of the oxygenated and de-oxygenated blood. Birds and mammals have four chambered heart. Blood goes through the heart twice during each cycle in them. This is known as double circulation.

Types of Blood Vessels

39. Capillaries: The smallest vessels have walls which are one-cell thick and are called capillaries. Their thin wall helps in exchange of material between the blood and surrounding cells. Veins are formed when the capillaries join together.

40. Role of blood platelets: Platelet cells circulate around the body in the blood and help in the clotting of blood when blood flows out during injury or cut.

41. Lymph or Tissue fluid: It is formed by the plasma, proteins and blood cells which escape into the intercellular spaces in the tissues through the pores present in the walls of the capillaries. Lymph is similar to the plasma of blood but colourless and contains less protein. It also carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space back into the blood. Lymph enters the lymphatic capillaries which join to form large lymph vessels that finally open into larger veins.

42. Transportation in Plants: Two main conducting pathways in plants are:
(i) Xylem and
(ii) Phloem

(i) Xylem: It carries water and minerals from the roots to other parts of the plants.

(ii) Phloem: It carries products of photosynthesis from leaves to the other parts of the plant.

43. Transport of Water and Minerals
(i) By root pressure: The cells of root in contact with soil actively take up ions which creates a difference in ion concentration between the root and the soil. Water moves into the root from the soil to eliminate this difference, creating a column of water that is steadily pushed upwards.

(ii) By transpiration pull: Loss of water from stomata by transpiration gets replaced by the xylem vessels in the leaf which creates a suction to pull water from the xylem cells of the roots. This strategy is used during day time and helps to transport water to the highest points of the plant body.

44. Transpiration and its roles: The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.
It helps in
(i) absorption and upward movement of water and minerals.
(ii) temperature regulation by cooling the leaf surface.

45. Transport of food and other substances: Translocation is the transport of soluble products of photosynthesis through phloem.
Sucrose is transferred into sieve tubes of phloem via the companion cells using energy from ATP. This increases the osmotic pressure inside the sieve tubes which causes movement of water into the sieve tubes from the adjacent xylem. This pressure helps in translocation of material in the phloem to tissues which have less pressure.

46. Excretion: Removal of metabolic wastes from the body is called as excretion.

47. Excretion in Unicellular organisms: Many unicellular organisms remove metabolic wastes from the body surface into the surrounding water by simple diffusion.

48. Excretion in Human Beings: Excretory system of human beings includes:
(i) A pair of Kidneys
(ii) A Urinary Bladder
(iii) A pair of Ureters
(iv) A Urethra The purpose of making urine is to filter out waste product from the blood i.e., urea which is produced in the liver. Each kidney has large numbers of filtration units called nephrons. The urine formation involves three steps.

(i) Glomerular filtration: Nitrogenous wastes, glucose water, amino acid filter from the blood in blood capillaries into Bowman Capsule of the nephrons.

(ii) Selective reabsorption: Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water are selectively reabsorbed back by capillaries surrounding the nephrons.

(iii) Tubular secretion: Some ions like K⁺, H⁺, etc. are secreted into the tubule which opens up into the collecting duct.

Urine produced in the kidneys passes through collecting duct into the ureters. Ureters takes urine into the urinary bladder where it is stored until it is released through the urethra. Release of urine is under nervous control.

49. Excretion in Plants: Excess oxygen and carbon dioxide removed through stomata. Excess water removed by transpiration through stomata.
Plant waste products are also removed by:

• Storage in cellular vacuoles
• Storage in leaves that fall off
• Storing as resins and gums in old xylem
• By excreting into the soil around them.

Class 10 Science Chapter 6 Notes Important Terms

Autotrophs: The organisms which can prepare their own food from inorganic substances by using light or chemical energy. For example, Green plants and Bacteria.

Heterotrophs: Organisms which cannot synthesise their own food and depend oh other organisms for their nutrition. For example, Humans.

Bio-catalysts: Enzymes are called as bio-catalysts as they play an important role in chemical reactions taking place in living organisms.

Photosynthesis: The process by which the green plants make their own food in the presence of carbon dioxide, water, chlorophyll and sunlight. The site of photosynthesis is chloroplast present in plant cells.

Ingestion: The process of taking in food into body of an organism.

Digestion: It is the breakdown of large insoluble food molecules into simpler and small water- soluble food molecules so that they can be absorbed into the blood stream.

Absorption: The process of passing the nutrients from the digested food into the blood stream from the walls of the intestine.

Assimilation: The process by which the absorbed food is used by the various cells and tissues of the body for growth and repair.

Egestion: The act or process of throwing out the undigested material from a cell or an organism is called as egestion.

Peristalsis: It is a series of wave-like muscle contractions of the muscles of the oesophagus that moves food into the stomach.

Emulsification: The breakdown of large fat globules in the duodenum into smaller globules in order to provide a larger surface area for the enzyme lipase to act and digest the fats into fatty acids and glycerol.

Inhalation: The process by which we take in air is called as inhalation. During inhalation, rib cage is moved up, diaphragm contracts (tightens) and moves downward to increase volume of chest cavity.

Exhalation: The process by which the air flows out of lungs is called as exhalation. During exhalation, the ribs relax; diaphragm relaxes and moves upward to reduce the volume of chest cavity.

Residual volume: The volume of air remaining in the lungs even after forceful exhalation is called residual volume.

Respiration: It is the biochemical process in which the cells of an organism obtain energy by combining oxygen and glucose, resulting in the release of carbon dioxide, water, and energy in the form of ATP.

Fermentation: It is a metabolic process which occurs under anaerobic conditions in yeast and bacteria to convert sugar to acids, gases or alcohol.

Haemoglobin: The respiratory pigment which helps to transport oxygen to various cells and tissues of the body.

Blood pressure: The force exerted by blood against the wall of a vessel is called blood pressure. It is measured by sphygmomanometer.

Translocation: It is the movement of materials from leaves to other tissues throughout the plant.

Transpiration: It is the evaporative loss of water by plants.

Nephron: It is the functional unit of kidney. It has two parts—the glomerulus and the renal tubule.

Haemodialysis: This is a process which helps in purifying the blood of a patient suffering from kidney problem or failure, using an artificial kidney. It removes nitrogenous waste products from the blood through dialysis.

On this page, you will find Periodic Classification of Elements Class 10 Notes Science Chapter 5 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 5 Periodic Classification of Elements will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 5 Periodic Classification of Elements

Periodic Classification of Elements Class 10 Notes Understanding the Lesson

1. At present, 118 elements are known to us. All these have different properties. Out of these 118, only 98 are naturally occurring. These elements have different characteristic properties, so it is very difficult to study these elements individually. Scientists made several attempts to classify elements according to their properties.

2. Dobereiner’s Triads (1817): He identified some triads (groups having three elements). Dobereiner showed that when the three elements in a triad were written in the order of increasing atomic masses; the atomic mass of the middle element was the average of the atomic masses of the other three elements. For example,

Dobereiner could identify only three triads from the elements known at that time. Hence, this system of classification into triads was not found to be useful.

3. Newland’s Law of Octaves (1866): He arranged the known elements in the order of increasing atomic masses. He found that every eighth element had properties similar to that of the first like the musical note. It is known as Newlands law of octaves.

4. Limitations

• Law of octaves was applicable only upto calcium.
• Discovery of Noble gases disturbed the octaves.
• Octaves worked well only for lighter elements.
• Properties of new elements could not fit in it.

5. Mendeleev’s Periodic Table

Mendeleev’s Periodic Law: Physical and chemical properties of elements are the periodic function of their atomic masses.
Mendeleev’s periodic table is based on the chemical properties of elements. Mendeleev’s periodic table contains vertical columns called ‘groups’ and horizontal rows called ‘periods’.

6. Achievements of Mendeleev’s Periodic Table: 63 elements were known at the time of classification.

• Elements with similar properties could be grouped together.
• Mendeleev left some gaps in his periodic table. Mendeleev boldly predicted the existence of some elements that had not been discovered at that time.
• Noble gases discovered, could be placed without disturbing the existing order.

Remember
Scandium, gallium and germa-nium have properties similar to Eka-boron, Eka-aluminium and Eka-silicon respectively.

7. Limitations of Mendeleev’s Classification

• The position of hydrogen in the table was not certain because it could be placed in the group of alkali metals as well as in halogens.
• Isotopes of elements were placed in the same position in the table though according to their atomic masses, they should have been placed in different positions.
• Certain elements of higher atomic mass preceed those with lower atomic mass. For example, tellurium (atomic mass 127.6) precedes iodine (atomic mass 126.9). Iodine was placed after tellurium though it had lower atomic mass because Iodine had properties similar to bromine and not selenium.

8. The Modern Periodic Table
Henry Moseley (1913) exhibited that the atomic number of an element is a more fundamental property than its atomic mass. Mendeleev’s periodic law was modified and atomic number was adopted as the basis of the modern periodic table.

9. The Modern Periodic Law states that:
The physical and chemical properties of the elements are the periodic function of their atomic numbers.
It means that if the elements are arranged in order of increasing atomic numbers, the elements with similar properties recur after regular intervals. Many new forms of periodic table have been proposed in recent times with modern periodic law as the guiding principle, but the general plan of the table remains the same as proposed by Mendeleev. The most commonly known periodic table is the Long form of the periodic table.

• Modern periodic table contains 18 vertical columns known as groups and 7 horizontal rows known as periods.
• Elements in a group have the same number of valence electrons.
• Number of the shells increases as we go down the group.
• Elements in a period have same number of shells.
• Number of elements placed in a particular period depends upon the fact that how electrons are filled into various shells.
• Maximum number of electrons that can be accommodated in a shell depends on the formula 2n² where n is the number of the given shell. For example, in K shell the number of electrons is 2 x (1)² = 2 in the first period, L shell – 2 x (2)² = 8 elements in the second period.
• Position of the element in the periodic table tells about its reactivity.

10. Trends in the Modern Periodic Table

Valency: Number of valence electrons present in the outermost shells. Valency remains the same down a group but changes across a period.

Atomic Size: Atomic size refers to radius of an atom.

Atomic size or radius decreases in moving from left to right along a period due to increase in nuclear charge. Atomic size increases down the group because new shells are being added as we go down the group.

Metallic Character: Metallic character means the tendency of an atom to lose electrons.

Metallic character decreases across a period because the effective nuclear charge increases, that means the tendency to lose electrons decreases. Metals are electropositive as they tend to lose electrons while forming bonds.

Class 10 Science Chapter 5 Notes Important Terms

Atomic number of an element is equal to the number of protons in the nucleus of its neutral atom.
Atomic number = Number of protons = Number of electrons

Electronic configuration corresponds to the distribution of electrons in the different shells.

Element is a chemical substance that cannot be decomposed by chemical means into simple substances. It contains the same kind of atoms.

Groups are the vertical rows in the periodic table.

Periods are the horizontal rows in the periodic table.

Periodic table is a tabular arrangement of elements in groups (vertical columns) and periods (horizontal rows) highlighting the regular trends in physical and chemical properties.

Shell is a region around the nucleus in an atom where electron revolves.

Valence shell is the outermost shell of an atom.

Periodicity. The properties which reoccur after a regular intervals in a periodic table are called periodic properties and the phenomenon is called periodicity of element.

Modern. Modern periodic law can be stated as follows:
“Physical and chemical properties of elements are a periodic function of their atomic number”.

On this page, you will find Carbon and its Compounds Class 10 Notes Science Chapter 4 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 4 Carbon and its Compounds will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 4 Notes Carbon and its Compounds

Carbon and its Compounds Class 10 Notes Understanding the Lesson

1. Carbon: All living structures are carbon based. The amount of carbon present in the Earth’s crust and in the atmosphere is quite meagre. The Earth’s crust has only 0.02% carbon in the form of minerals (like carbonates, bicarbonates, coal and petroleum) and the atmosphere has 0.03% carbon dioxide.

2. Covalent Bond in Carbon
The atomic number of carbon is 6 and its electronic configuration is 2, 4.
To attain a noble gas configuration it could gain four more electrons in its valence shell or loose the four electrons from its valence shell.

• It is difficult for an atom of carbon to either gain or lose electrons as it would be difficult to hold the extra electrons and would require a large amount of energy to remove four electrons.
• Carbon attains the noble gas configuration by sharing its valence electrons with other atoms. Atoms of other elements like hydrogen, oxygen, nitrogen, chlorine also show sharing of valence electrons.

• It is evident that the number of shared pair of electrons can be one, two or three. Try making the structures of H₂O and CH₄.
• Bond formed by the sharing of an electron pair between two atoms is called covalent bond.
• Covalently bonded molecules have low melting and boiling points because of comparatively weaker intermolecular forces, unlike ionic compounds.
• These molecules are generally poor conductors of electricity since no charged particles are formed.

3. Versatile Nature of Carbon Atoms
Two important properties which enable carbon to form enormously large number of compounds.

(i) Catenation is property of carbon atom to form bonds with other atoms of carbon. Like carbon, silicon forms compounds with hydrogen which have chains upto seven or eight atoms of silicon.
The property of catenation is shown by other elements also but carbon exhibits this property to maximum extent. This is due to greater strength of carbon-carbon bond.

(ii) Tetravalency of the carbon atom: Carbon has four valence electrons (At. No. of C = 6, Electronic Configuration = 2, 4) since it can neither lose nor gain electrons to attain octet, it forms covalent bonds by sharing its four electrons with other atoms. This characteristic of the carbon atom, by virtue of which it forms four covalent bonds, is called the tetravalency of carbon.

Saturated and unsaturated carbon compounds: Organic compounds in which carbon atoms are bonded together with a single bond and then use the hydrogen atoms to satisfy the remaining valencies of carbon, are known as saturated compounds. For example,

On another hand hydrocarbons containing multiple bond i.e., C=C, C≡C are known as unsaturated carbon compounds. The unsaturated hydrocarbons which contain one or more double bonds are called alkenes. Those containing one or more triple bond are called alkynes.

Examples
Alkene:               CH₂=CH₂ (Ethene)
Alkyne:                CH≡CH (Ethyne)

4. Functional group: Atom or group of atom which provides certain characteristic properties to the compound, is known as functional group. The functional group is attached to the carbon chain through the valency by replacing one hydrogen atom or atoms.

5. Homologous series: A series or a family of organic compounds having the same functional group, similar chemical properties and successive (adjacent) member of which differ by a —CH2 unit or 14 mass units, is known as homologous series. The individual members of the series are called homologous.

6. General Characteristics of Homologous Series
(i) All the members of a homologous series can be represented by a general chemical formula.

Alkane :C_nH_{2n + 2}[CH₄,C₂H₆,C₃H₈ …]
Alkene : C_nH_2n [C₂H₄, C₃H₆, C₄H₈ …]
Alkyne : C_nH_2n–2 [C₂H₂, C₃H₄, C₄H₆ …]

(ii) All the members of a given homologous series have the same functional group.
(iii) A homologous series exhibit similar chemical properties.
(iv) In a homologous series as the molar mass increases, a gradation in physical properties is observed. It is due to fact that the melting points and boiling points increases with increasing molar mass.

7. Nomenclature of Carbon Compounds
An organic compound may have a common name, a systematic name and IUPAC names. IUPAC names are now universally adopted.
Rules for naming of organic compounds: IUPAC name of organic compound consists of four parts. These are arranged in the sequence given below:
Prefix + Word root + Primary suffix + Secondary suffix

(1) In IUPAC system prefix denotes the substituent group. The prefixes for a few substituent groups are as follows:

Remember
The International Union of Pure and Applied Chemistry (IUPAC) devised a method of systematically naming of organic compounds, which is termed as IUPAC system.

Some important points for writing IUPAC names:

• Select the longest carbon chain as a parent chain.
• The parent chain must include carbon atoms including multiple bond (= or ≡ bond) and the terminal functional groups
  ( – CHO  – COOH, etc).
• Parent chain should be numbered in such a way that multiple bond/functional group get lowest number.
• The position of the multiple bond must be indicated by a numerical prefix.
• If the name of the functional group is to be given as a suffix, the name of the carbon chain is modified by deleting the final ‘e’ and adding the appropriate suffix.

2. In IUPAC name Word root denotes the number of carbon atoms in the longest selected parent chain.

3. Primary suffix is used to denote the nature of carbon-carbon bond.

4. Secondary suffix is used to denote the functional group present in the organic compound. It is attached to the primary suffix. Some common functional groups and their secondary suffix are listed below: Example: Write the IUPAC names to the following compounds.

Addition Reaction
A chemical reaction in which two or more chemical substances get combined and gives a single product, is known as addition reaction.
For example,
(i) Unsaturated hydrocarbons add hydrogen in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons.

(ii) Addition reaction also used in the hydrogenation of vegetable oils, which gives vegetable ghee, have saturated carbon chains.

Vegetable ghee!animal fat contains saturated fatty acids which are said to be harmful for health.

(iii) Addition of bromine

Substitution Reaction
A chemical reaction in which one type of atom or a group of atoms get displaced or substituted by some other atom or group of atoms is known as substitution reaction. For example, in the presence of sunlight, chlorine is added to hydrocarbon. In this chemical reaction chlorine can replace the hydrogen atoms one by one.

Similarly, the remaining three H atoms will be also replaced by Cl atoms one by one.

Some Important Carbon Compounds
(A) Ethanol or Ethyl alcohol
Ethanol is the second member of the homologous alcohol series. The structural formula of ethanol is:

Physical properties

• Ethanol is liquid at room temperature.
• Ethanol is soluble in water in all proportions.
• It boils at 351 K (78°C).
• It is neutral towards litmus.
• It is a non-conductor of electricity because it does not contain ions.

Chemical Reactions
1. Reaction with sodium: Hydrogen gas is evolved by the reaction of ethanol with sodium.

This reaction is a test for alcohols.

2. Dehydration: Heating ethanol at 443K with excess cone. H2S04 results alkene (Unsaturated hydrocarbon).

Here sulphuric acid acts as a dehydrating agent.

Alcohol as a Fuel
Sugar cane juice can be used to prepare molasses which is fermented to give ethanol. Some countries now use alcohol as an additive in petrol since it is a cleaner fuel which gives rise to only CO₂ and H₂O on burning in sufficient air (oxygen). Chemical reaction involved is given as

Denatured Alcohol
To prevent the misuse of ethanol, it is made unfit for drinking by adding poisonous substances (like methanol, pyridine, CuSO₄, etc.) to it, this is called denatured alcohol.
Dyes are also added to colour the alcohol blue so that it can be identified easily.

How does alcohol affect human beings?
Ethanol (C₂H₅OH) is a chief constituent of all alcohol beverages (beer, wine, whisky, etc). In case someone consumes large amount daily, it has very harmful effect, it may even cause death by damaging liver and kidney.

Uses of ethanol

• Ethanol is a main constituents of all alcoholic beverages.
• Ethanol is used to sterilise wounds and syringes.
• It is used as a solvent for paints, lacquers, varnishes, cosmetics, perfumes, etc.
• It is also used as a fuel in stoves and spirit lamps.

(B) Ethanoic acid or Acetic acid
The group of organic acids are known as carboxylic acids. However, unlike mineral acids like HCl, carboxylic acids are weak acids. Ethanoic acid is the second member of the homologous alcohol series. The structural formula of ethanoic acid is:

Physical Properties

• Ethanoic acid is a colourless liquid with sour taste.
• It is miscible with water in all proportions.
• Being acidic nature, ethanoic acid turns blue litmus solution red.
• Acetic acid boils at 39 IK (118°C).
• 5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles.
• Melting point of pure ethanoic acid is 290 K and hence it often freezes during winter in cold climates. This gave rise to its name glacial acetic acid.

Chemical reactions of ethanoic acid
1. Esterification reaction: Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst and gives ester as a product. Esters are sweet smelling substances.

On treating with alkali, sodium hydroxide (NaOH), the ester is converted back to alcohol and sodium salt of carboxylic acid. This is known as saponification reaction.

2. Reaction with base: Ethanoic acid reacts with a base such as sodium hydroxide (NaOH) to give a salt and water.
\(\mathrm{NaOH}+\mathrm{CH}_{3} \mathrm{COOH} \longrightarrow \mathrm{CH}_{3} \mathrm{COONa}+\mathrm{H}_{2} \mathrm{O}\)

3. Reaction with carbonates and hydrogencarbonate: Ethanoic acid reacts with carbonates and hydrogencarbonates to give rise to a salt, CO₂ and water. The salt produced is sodium acetate.
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

Uses of ethanoic acid

• It is used as a solvent.
• It is used for making dyes, perfumes and medicines.
• It is also used as vinegar which is a preservative for pickles.

Soaps and Detergents

• Soap is sodium and potassium salt of carboxylic acids with long chain.
• Soaps are effective with soft water only and ineffective with hard water.
• Detergents are ammonium or sulphonate salts of carboxylic acids with long chain. They are effective with both soft as well as hard water. An ionic part (hydrophilic) and a long hydrocarbon chain (hydrophobic) part constitutes the soap molecule.

Cleansing Action of Soaps

• Most dirt is oily in nature and the hydrophobic end attaches itself with dirt, while the ionic end is surrounded with molecules of water. This result in formation of a radial structure called micelles.
• An emulsion is thus formed by soap molecule. The cloth needs to be mechanically agitated to remove the dirt particles from the cloth.
• Scum: The magnesium and calcium salts present in hard water reacts with soap molecule to form insoluble products called scum, thus obstructing the cleansing action. Use of detergents overcome this problem as the detergent molecule prevents the formation of insoluble product and thus clothes get cleaned.

Class 10 Science Chapter 4 Notes Important Terms

Dehydration is loss of water during a chemical reaction.

Hydration is gain of water during a chemical reaction.

Combustion means heating/burning of a compound with excess of air or oxygen. It is exothermic in nature.

Esterification is a chemical reaction in which a carboxylic acid reacts with an alcohol to form an ester.

Fermentation is the slow decomposition of big organic molecules into simpler molecules in presence of enzymes.

On this page, you will find Metals and Non-metals Class 10 Notes Science Chapter 3 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 3 Metals and Non-metals will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 3 Notes Metals and Non-metals

Metals and Non-metals Class 10 Notes Understanding the Lesson

1. Element is the simplest form of matter which contains one kind of atoms. About 118 elements are known today. There are more than 90 metals, 22 non-metals and a few metalloids.

• Sodium (Na), potassium (K), magnesium (Mg), aluminium (Al), calcium (Ca), Iron (Fe), Barium (Ba) are some metals.
• Oxygen (O), hydrogen (H), nitrogen (N), sulphur (S), phosphorus (P), fluorine (F), chlorine (Cl), bromine (Br), iodine (I) are some non-metals.

2. Physical Properties of Metals

• Metals in their pure state, have a shining surface. This property is called metallic lustre.
• Metals can be beaten into thin sheets. This property is called Gold and silver are the most malleable metals.
• Metals have ability to be drawn into thin wires. This property is called ductility. Gold is the most ductile metal.
• Metals are good conductors of heat and have high melting points. The best conductor of heat are silver and copper. Lead and mercury are comparatively poor conductors of heat.
• The metals that produce a sound on striking a hard surface are said to be
• Alkali metal (Li, Na, K) are so soft that they can be cut with a knife. They have low densities and low melting points.
• Metals have high melting point but gallium and caesium have very low melting points. These two metals will melt if you keep them on your palm.

3. Physical Properties of Non-Metals

• Non-metal are either solids or gases except bromine which is a liquid.

4. Some other exceptions:

• Iodine is a non-metal but it is lustrous.
• Carbon is a non-metal which exist in two allotropic forms: diamond and graphite. Diamond is the hardest substance with a very high melting point. Graphite is a conductor of electricity.

5. Chemical Properties of Metals

I. All metals combine with oxygen to form metal oxides.
Metal + Oxygen → Metal oxide
For example,
2Cu + O₂ → 2CuO
4Al + 3O₂ → 2Al₂O₃

6. Remember
Different metals exhibit different reactivity towards oxygen. Metals such as K and Na react so vigorously that they catch fire if kept in the open. Hence, to protect them they are kept immersed in kerosene oil.

Generally metal oxides are basic in nature. But some oxides like aluminium oxide, zinc oxide show both acidic as well as basic behaviour.

Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

Most metal oxides are insoluble in water but some of these dissolve in water to form alkalies. Sodium oxide and potassium oxide dissolve in water to produce alkali as follows:

Na₂O(s) + H₂O(l) → 2NaOH(aq)
K₂O(s) + H₂O(l) → 2KOH(aq)

II. Metals react with water and produce a metal oxide and hydrogen gas. Metal oxides that are soluble in water dissolve in it further to form metal hydroxide. But all metals do not react with water.

Metal + Water → Metal Oxide + Hydrogen
Metal Oxide + Water → Metal hydroxide

Potassium and sodium react violently with cold water. The reaction is exothermic, so the released hydrogen catches fire immediately.

2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g) + Heat
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Heat

The reaction of calcium with water is less violent. The heat evolved is not sufficient for the hydrogen to catch fire.
Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)
Mg(s) + 2H₂O(l) → Mg(OH)₂(aq) + H₂(g)

• Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.
• Magnesium does not react with cold water. It reacts with hot water to form magnesium hydroxide and hydrogen.

Aluminium, iron and zinc do not react either with cold or hot water. But they react with steam to form the metal oxide and hydrogen.

2Al(s) + 3H₂O(g) → Al₂O₃(s) + 3H₂(g)
3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

Lead, copper, silver and gold do not react with water at all.

III. Metals react with acids to give a salt and hydrogen gas.
Metal + Dilute acid → Salt + Hydrogen

• Hydrogen gas is not evolved when a metal reacts with HNO₃. It is because HNO₃ is a strong oxidising agent. It oxidises the H₂ produced to water and itself get reduced to any of the nitrogen oxides.
• Magnesium (Mg) and manganese (Mn) react with very dilute HNO₃ to evolve H₂
• Copper does not react with dilute HCl.

IV. Reactive metals can displace less reactive metals from their compounds in solution or molten form.

Metal A + Salt solution of B → Salt solution of A + Metal B

Fe + CuSO₄ → FeSO₄ + Cu
Zn + CuSO₄ → ZnSO₄ + Cu
Reactivity of metal can be explained on the basis of displacement reactions

7. Knowledge Plus
Aqua regia (Latin for ‘royal water) is a freshly prepared mixture of concentrated HCl and concentrated nitric acid in the ratio of 3:1. It is a highly corrosive, fuming liquid and dissolve gold and platinum.

8. The Reactivity Series
The reactivity series is a list of metals arranged in the order of their decreasing activities.

Metals occupying higher position in the series have more tendency to lose electrons and are more reactive. The metals at the bottom of the series are least reactive. Thus, potassium is the most reactive metal.

9. How do metals and non-metals react?

Reactivity is the tendency of elements (metals and non-metals) to attain a completely filled valence shell. Metal atoms having 1, 2 or 3 electrons in their outermost shell can lose electrons to non-metal atoms having 5,6 or 7 electrons to attain the electronic configuratìoñ of the nearest noble gas (i.e., completely filled valence shell).

Thus the metal atom becomes a positively charged ion or cation and the non-metal atom becomes a negatively charged ion or anion. The cation and anion being oppositely charged attract each other and are held by strong electrostatic forces of attraction to exist as an ionic compound. For example,

Metal ore heated strongly in limited or no supply of air (Calcination).

10. Reduction of Metal Oxide:

(i) Using coke: Coke as a reducing agent.

(ii) Using displacement reaction: Highly reactive metals like Na, Ca and A1 are used to displace metals of lower reactivity from their compounds. These displacement reactions are highly exothermic.

11. Thermite Reaction: Reduction of a metal oxide to form metal by using aluminium powder as a reducing agent. This process is used to join broken pieces of heavy iron objects or welding.

12. Extracting Metals at the Top of the Activity Series:

• These metals have more affinity for oxygen than carbon so they cannot be obtained from their compounds by reducing with carbon.
• They are obtained by electrolytic reduction, for example, Sodium is obtained by electrolysis of its molten chloride                     NaCl→ Na⁺ + Cl^–

As electricity is passed through the solution, metal gets deposited at the cathode and non-metal at the anode.

• At cathode: Na⁺ + e^– →Na
• At anode: 2Cl^– →Cl₂ (g) + 2e^–

III. Refining of Metals

• Impurities present in the obtained metal can be removed by electrolytic refining.

Copper is obtained using this method. Following are present inside the electrolytic tank.

• Anode – slab of impure copper
• Cathode – slab of pure copper
• Solution – aqueous solution of copper sulphate with some dilute sulphuric acid.
• From anode, copper ions are released in the solution and equivalent amount of copper from solution is deposited at cathode.
• Insoluble impurities containing silver and gold gets deposited at the bottom of anode as anode mud.

13. Corrosion

• Metals are attacked by substances in the surroundings like moisture and acids.
• Silver—It reacts with sulphur in air to form a black coating of silver sulphide.
• Copper—It reacts with moist carbon dioxide in air and forms a green coating of copper carbonate.
• Iron—acquires a coating of a brown flaky substance called rust. Both air and moisture are necessary for rusting of iron. Rust is hydrated Iron (III) oxide e., Fe₂O₃.xH₂O

14. Prevention of Corrosion

• Rusting of iron is prevented by painting, oiling, greasing, galvanizing, chrome plating, anodising and making alloys.
• In galvanization, iron or steel is coated with a thin layer of zinc. Zinc oxide formed due to oxidation is impervious to air and moisture protecting further layers from corrosion.

15. Alloys: These are homogeneous mixture of metals with metals or non-metals.
Adding small amount of carbon makes iron hard and strong.

Class 10 Science Chapter 3 Notes Important Terms

Corrosion is the eating up of metals by the action of air, moisture or a chemical on their surface.

Rust is mainly hydrated iron (III) oxide Fe₂O₃.xH₂O due to corrosion.

Ores are the minerals from which metals can be extracted conveniently and profitably.

Minerals are natural materials in which the metals or their compounds are found in the Earth.

Covalent bond is the chemical bond formed by sharing of electrons between two atoms. Aqua-regia is a freshly prepared mixture of 1 part of concentrated nitric acid and 3 parts of concentrated hydrochloric acid.

Brass is an alloy of copper and zinc. Bronze is an alloy of copper and tin.

Metallurgy is the process of extraction of a metal from its ore and its refining.

Activity series is the arrangement of metals in the order of decreasing reactivity.

On this page, you will find Acids Bases and Salts Class 10 Notes Science Chapter 2 Pdf free download. CBSE NCERT Class 10 Science Notes Chapter 2 Acids Bases and Salts will seemingly help them to revise the important concepts in less time.

CBSE Class 10 Science Chapter 2 Notes Acids Bases and Salts

Acids Bases and Salts Class 10 Notes Understanding the Lesson

1. Acids and Bases: Acids are sour in taste and change the colour of blue litmus to red. The term has been derived from the Latin word ‘acidus’ which means sour taste. Generally acids have atleast one or more hydrogen atoms in their formulae.

An acid may be defined as a chemical substance which releases one or more H⁺ or HsO⁺ ions in aqueous solution.
For example, HCl, HNO₃, H₂SO₄, etc.

Bases are bitter and change the colour of the red litmus to blue. Generally bases have one or more hydroxyl (OH^–) groups. They produce hydroxyl ions (OH^–) when dissolved in water.

A base may be defined as a chemical substance which releases one or more OH^– ions in aqueous solution.
For example, NaOH, KOH, etc.

• Acid-Base indicator: Natural/synthetic materials which indicate the presence of acid or base in a solution, are called acid base indicator or simply indicator.
• Litmus solution: It is a purple dye which is extracted from lichen, a plant belonging to the division
  .
• Phenolphthalein: It is a colourless organic dye in acidic or neutral medium but it changes to pink in basic medium.
• Methyl orange: It is an orange coloured dye and keeps this colour in the neutral medium. In the acidic medium, the colour of the indicator becomes red and in the basic medium, it changes to yellow.
• Red cabbage juice: Its colour remains red in acidic medium but changes to green if the medium is basic or alkaline.
• Turmeric solution: It is a yellow dye and in the acidic as well as neutral medium, its colour remains yellow. In the basic medium the colour changes to reddish brown.

2. Olfactory indicators: These are chemical substances whose odour changes in acidic or basic medium.
For example, onion, vanilla and clove oil.

3. Reaction of acid or base with metal: Metals react with acids to liberate hydrogen gas and form salt.
Acid + Metal → Salt + Hydrogen gas

A few metals like zinc, lead and aluminium react with bases to give off hydrogen.

4. Reaction of acids with metal hydrogen carbonate and metal carbonates: All metal carbonates and hydrogen carbonates react with acids to give the corresponding salt, carbon dioxide and water.

Metal carbonate + Acid → Salt + H₂O + CO₂
Metal hydrogen carbonate + Acid → Salt + H₂O + CO₂

For example,
Na₂CO₃(s) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)
NaHCO₃(s) + HCl(ag) → NaCl(aq) + H₂O(Z) + CO₂(g)

The released CO₂ gas turns lime water milky due to formation of CaCO₃.

On passing excess CO₂, the milky white precipitate dissolves in water.

5. Neutralisation reaction: A chemical reaction between an acid and a base to give a salt and water is known as neutralisation reaction. In general neutralisation reaction can be written as

Base + Acid → Salt + Water
NaOH(aq) + HCl(aq) → NaCl(aq) + H₂O(l)

(i) Reactions of metal oxides with acids

(ii) Reactions of non-metallic oxide with base
Non-metallic oxide + Base→ Salt + Water
CO₂ + Ca(OH)₂ → CaCO₃ + H₂O

How strong are acid or base solutions: Any aqueous solution, be it acidic, alkaline or neutral, will have both H⁺ and OH^– ions.
The  solution will be acidic or alkaline depending upon which of the two ions is present in larger concentration.

A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed. pH scale was given by a Danish chemist Sorensen. The p in pH stands for ‘potenz’ in German meaning ‘power’.

pH should be thought of simply as a number between 0-14 which indicates the acidic or basic nature of a solution. Higher the hydrogen ion concentration, lower is the pH value.

Knowledge +
pH = negative logarithm to the base 10 of the H⁺ ion concentration.
The concentration is in mol/dm³. pH = – log H⁺

Remember: Every one fold change in the pH scale brings about a ten-fold change in H⁺ ion concentration. The strength of acids and bases depends on the concentration of H⁺ ion and OH^–.

If we take two acids HCl and CH₃COOH of the same concentration, then they produce different amount of H⁺. Acids that give rise to more H⁺ ions are said to be strong acids and acids that give less H⁺ ions are said to be weak acids.

6. Importance of pH in everyday life:

(i) If pH of rain water is less than 5.6, it is called acid rain. When acid rain flows into the rivers, it lowers the pH of river water. The survival of aquatic life in such rivers become difficult. Acid rain also damage crops and cause a change in pH of the soil.

(ii) pH in our digestive system: Our stomach produces digestive juices/hydrochloric acid (HCl), which helps in the digestion of food without harming the stomach. However, sometimes the stomach produces too much of acid and this causes indigestion, which is accompanied by pain and irritation. To get rid of this pain, people use antacids like magnesium hydroxide. These antacids neutralise the excess acid formed.

(iii) pH change as the cause of tooth decay: Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel, made up of calcium phosphate is the hardest substance in the body. It does not dissolve in water but is corroded when the pH in the mouth is below 5.5. Using toothpaste, which are generally basic, for cleaning the teeth can neutralise the excess acid and prevent tooth decay.

(iv) Bee-sting leaves an acid which causes pain and irritation. Using a mild base like baking soda on the stung area gives relief. Stinging hair of nettle leaves inject methanoic acid causing a burning pain. A traditional remedy is rubbing the area with the leaf of the dock plant.

(v) Various fluids in our body work within a particular range of pH such as, pH of human blood should be between 7.3 to 7.5.

(vi) For the growth of plants, a particular pH range of soil is essential. Usually neutral soil is best for crops. If the soil is acidic, farmers treat the soil with quick lime or slaked lime.

(vii) The tarnished surface of a copper vessel due to the formation of copper oxide layer (which is basic) can be cleaned by rubbing with lemon (which is acidic).

7. Salts: Salts are generally ionic compounds which are obtained by neutralisation reaction between acids and bases.

Acid + Base→ Salt + Water
HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(Z)

In these salts, the cation is derived from base and anion is derived from acid.
Salts are mostly solids with high melting points. They are soluble in water.

Different types of salts:

• Normal salts : NaNO₃
• Acidic salts : NaHSO₄
• Basic salts : Pb(OH)Cl
• Double salts : FeSO₄.(NH₄)₂.SO₄.6H₂O

8. Remember: Salts of a strong acid and a strong base are neutral with pH value of 7. On the other hand, salts of strong acid and weak base are acidic with pH values less than 7 and those of strong base and weak acid are basic in nature, with pH value more than 7.

Common Salt (NaCl) [Table salt]
Sodium chloride (NaCl) also called common salt or table salt is the most common/essential part of our diet. It is obtained by neutralisation reaction of sodium hydroxide (NaOH) with hydrochloric acid (HC1).

It is obtained on a large scale from sea water.
Large crystals are often brown due to the presence of impurities. This is called rock salt. Beds of rock salt were formed when seas of by gone ages dried up. Rock salt is mined like coal.

9. Uses of Sodium Chloride

• Sodium chloride is a major ingredient of edible salt.
• It is used as a food preservative.
• Compounds like sodium hydroxide (NaOH), baking soda (NaHCO₃) and washing soda are obtained from sodium chloride.
• It is used to melt ice on hill stations and cold countries during heavy snow fall.

10. Sodium Hydroxide (NaOH): Sodium hydroxide (NaOH) is commonly known as caustic soda.

Sodium hydroxide is manufactured by electrolysis of an aqueous solution of sodium chloride (called brine). Chlorine gas is given off at the anode and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode.
2NaCl(aq) + 2H₂O(l) → 2NaOH(ag) + Cl₂(g) + H₂(g)

The process is called the chlor-alkali process because of the products formed chlor for chlorine and alkali for sodium hydroxide.

11. Uses of Sodium Hydroxide

1. Sodium hydroxide is used for making soaps and detergents.
2. Sodium hydroxide is used for making artificial textile fibres (such as rayon).
3. It is used the preparation of soda lime (a mixture of NaOH and CaO).
4. It is used as a cleansing agent for machines and metal sheets.

12. Baking Soda (NaHCO_s): The chemical name of baking soda is sodium hydrogencarbonate or sodium bicarbonate (NaHCO₃). It can be prepared from sodium chloride as
NaCl + H₂O + CO₂ + NH₃→ NH₄Cl + NaHCO₃

Since it is slightly soluble in water, it can be removed by filtration.
It is a mild non-corrosive base. The following reaction takes place when it is heated during cooking.

13. Uses of Baking Soda
Being alkaline it is an ingredient in antacids. It neutralises excess acid in the stomach and provides relief.
NaHCO₃ + HCl → NaCl + H₂O + CO₂

• It is used in soda-acid fire extinguisher.
• It is used in making baking powder (a mixture of baking soda and mild edible acid like tartaric acid). When baking powder is heated or mixed in water CO₂ gas is released.
  NaHCO₃ + H⁺→ CO₂ + H₂O + Sodium salt of acid

The released CO₂ causes breads or cakes to rise making them soft and spongy/fluffy.

14. Bleaching Powder [CaOCl₂]: Bleaching powder is calcium oxychloride. It is also known as chloride of lime. Bleaching powder can be prepared by the action of chlorine on dry slaked lime [Ca(OH₂)].
Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O
Bleaching powder is a yellowish white solid.

15. Uses of Bleaching Powder

• It is an oxidising agent.
• It is used for disinfecting drinking water to make it free from germs.
• The most important use of bleaching powder is in:
• textile industry for bleaching cotton and linen
• paper industry for bleaching wood pulp
• laundry for bleaching washed clothes.

16. Washing Soda [Na₂Og.10H₂O]: Sodium carbonate is obtained by heating baking soda. When the sodium carbonate obtained by the above process is recrystallised, we get washing soda.
Na₂CO₃ + 10H₂O → Na₂CO₃.10H₂O
Anhydrous sodium carbonate is called soda ash.

17. Uses of Washing Soda

• It is used in glass, soap and paper industries.
• It is used in the manufacture of borax.
• It is used as a cleaning agent for domestic purposes.
• It is used for removing permanent hardness of water.

18. Plaster of Paris \(\left(\mathrm{CaSO}_{4} \cdot \frac{1}{2} \mathrm{H}_{2} \mathrm{O}\right)\)
Plaster of Paris is calcium sulphate hemihydrate, it can be obtained by heating gypsum at 373 K.
Plaster of Paris is a white powder and on mixing with water, it changes to gypsum once again giving a hard solid mass.

19. Knowledge Booster
In washing soda, (Na₂CO₃.10H₂O), 10H₂O signify water of crystallisation. Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt. Some other examples are

20. Uses of Plaster of Paris

• Plaster of Paris is used by doctors as plaster for supporting fractured bones in the right position.
• It is also used for making toys, materials for decoration and for making surfaces smooth.

Class 10 Science Chapter 2 Notes Important Terms

Alkalies are water soluble bases.

Rock salt is chemically sodium chloride (NaCl).

Antacid is a substance which can neutralise acidity in the stomach.

Neutralisation is the reaction in which an acid reacts with a base to form salt and water.

Bleaching powder is chemically calcium oxychloride (CaOCl₂) and is formed by passing chloride gas through dry slaked lime.

Amphoteric compound is a compound that can act both as an acid and a base.

Dilute Acid: Contains only a small amounts of acid and a large amount of water.

Concentrated Acid: A concentrated acid contains a large amount of acid and a small amount of water.