CBSE Class 7

On this page, you will find Heat Class 7 Notes Science Chapter 4 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 4 Heat will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 4 Notes Heat

Heat Class 7 Notes Understanding the Lesson

1. Heat is a form of energy.

2. The hotness and coldness of a body is relative.

3. Our sense of touch is not always a reliable guide to the degree of hotness of an object.

4. The measure of degree of hotness of an object is called temperature.

5. Thermometer is a device which is used to measure temperature.

6. The thermometer that measures our body temperature is called a clinical thermometer.

7. Clinical thermometer consists of a long, narrow, uniform glass tube and a bulb at one end. It has a kink which prevents mercury level from falling on its own. The range of this thermometer is from 35°C to 42°C (Fig. 4.1).

8. The normal temperature of human body is 37°C.

9. To measure the temperature of non-living objects, a laboratory thermometer is used. The range of laboratory thermometer is from -10°C to 110°C. (Fig. 4.2).

10. Nowadays, a digital thermometer is used instead of a clinical thermometer. It has no mercury in it.

11. Heat always flows from higher temperature to lower temperature. The three ways in which heat can flow from one object to another are conduction, convection and radiation.

12. The process by which heat is transferred from the hotter end to the colder end of an solid object is known as conduction.

13. The materials which allow heat to pass through them easily are called conductors. For example, iron, copper, zinc, etc.

14. The material which do not allow heat to pass through them easily are called poor conductors or insulators. For example, plastic, rubber, wood, etc.

15. Convection is the process of transferring heat from a hotter region to cooler region by the actual movement of particles. It generally occurs in liquid and gaseous medium.

16. Convection takes place when the air near the heat source gets hot and rises. The air from sides comes in to take its place.

17. The flow of cool air from the sea towards the land to replace the hot air on land, is called sea breeze [Fig. 4.3(a)]. This phenomenon takes place during the day.

18. During the night, the currents of air flow from the cooler land towards the warmer sea. This is called land breeze. [Fig. 4.3(b)],

19. The process of transmission of heat without any contact between the source and the object is called radiation.

20. All hot bodies radiate heat.

21. Dark-coloured objects absorb radiation better than the light-coloured objects. That is the reason we feel more comfortable in light-coloured clothes in the summer.

22. Woollen clothes keep us warm during winter. This is because wool is a poor conductor of heat and it has air trapped in between the fibres.

Class 7 Science Chapter 4 Notes Important Terms

Celsius scale: Celsius scale or centigrade scale is the unit used for measurement of temperature. It is a metre scale of temperature.

Conduction: The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction.

Conductor: The material which allow heat to pass through them easily is called conductor.

Convection: The process of transferring heat from a hotter region to cooler region by the actual movement of particles is called convection.

Insulator: The material which do not allow heat to pass through them easily is called insulator.

Land breeze: The process of flowing of air currents from the cooler land towards the warmer sea is called land breeze.

Radiation: The process of transfer of heat in which no medium is required is called radiation.

Sea breeze: The flow of cool air from the sea towards the land to replace the hot air on land is called sea breeze.

Temperature: The reliable measure of the hotness of an object is called temperature.

Thermometer: A device used to measure the temperature is called thermometer.

On this page, you will find Fibre to Fabric Class 7 Notes Science Chapter 3 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 3 Fibre to Fabric will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 3 Notes Fibre to Fabric

Fibre to Fabric Class 7 Notes Understanding the Lesson

1. Silk and wool are animal fibres because silk comes from silkworms and wool is obtained from fleece, i.e., hairs of sheep, goat, yak and some other animals.

2. The wool-yielding animals bear a thick coat of hair on their body. Hair keeps these animals warm because hair trap air which does not let the heat release from their body due to its poor conductivity.

3. The hairy skin of the sheep has two types of fibres that form the fleece:

• the coarse beard hair; and
• the fine soft under hair close to the skin.
• The fine hair provides the fibres for making wool.

4. Some breeds of sheep have only fine under-hair. Their parents are specially chosen to give birth to sheep with fine under-hair only. This process of selecting parents for obtaining special characters in their offsprings, such as soft under-hair in sheep, is called selective breeding.

5. Apart from sheep, wool is also obtained from yak, angora goat, camel, Lama and alpaca.

6. Sheep are reared in many parts of our country for wool. Certain breeds of sheep have thick coat of hair on their body which yields good quality of wool. Once the reared sheep have developed a thick growth of hair, hair is shaved off for obtaining wool.

7. Wool production involves various steps. The hair of the wool yielding animals is cut and processed into wool. Different steps are shearing, scouring, sorting, grading, dyeing and making yarn.

8. The rearing of silkworms for getting silk is called sericulture.

9. Silkworms are caterpillars of silk moth which feed on leaf of mulberry.

10. During their life cycle, the worms spin cocoons of silk fibres.

11. Silk fibres are made of protein.

12. Silk fibres from cocoons are separated out by reeling the silk.

13. Reeling is done in special machines, which unwind the threads or fibres of silk from the cocoon. Silk fibres are then spun in threads and then into cloth.

Class 7 Science Chapter 3 Notes Important Terms

Cocoon: Caterpillar completely covers itself by silk fibres and turns into pupa. This covering is known as cocoon.

Fleece: Hair on the body or outer coat of sheep or yak is called fleece. It is the source of wool.

Reeling: The process of taking out threads from the cocoon for use as silk is called the reeling the silk.

Scouring: The sheared skin with hair is thoroughly washed in tanks to remove grease dust and dirt. This is called scouring.

Sericulture: The production of raw silk by raising silkworms is called sericulture.

Shearing: The process of removing fleece of the sheep along with a thin layer of skin from its body is called shearing.

Silkmoth: The silk moth develops from pupa inside the cocoon. The silk yarn or thread is obtained from the cocoon of the silk moth.

Sorting: Separation of hairy skin in different textures is called sorting.

Caterpillars: The female silk moth lays eggs; from which worm-like larva called caterpillars or silkworms are hatched.

Mulberry silk moth: The most common silk moth, Bombyx mori, is known as mulberry silk moth.

On this page, you will find Nutrition in Animals Class 7 Notes Science Chapter 2 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 2 Nutrition in Animals will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 2 Notes Nutrition in Animals

Nutrition in Animals Class 7 Notes Understanding the Lesson

1. All organisms including humans require food for growth, repair and functioning of the body.

2. Animal nutrition includes:

• nutrient requirement,
• mode of intake of food and,
• its utilisation in the body.

3. Different organisms have different ways of taking food. For example, snakes swallow their prey, bees and hummingbirds suck nectar from the flowers, etc.

4. The human digestive system consists of the alimentary canal and secretory glands. The canal can be divided into various compartments

• the buccal cavity,
• food pipe or oesophagus,
• stomach,
• small intestine,
• large intestine ending in the rectum and
• the anus.

5. These parts together from the digestive tract.

6. The digestive tract and the associated glands (like salivary gland, liver, pancreas) together constitute the digestive system.

7. Nutrition is a complex process involving

• ingestion,
• digestion,
• absorption,
• assimilation and
• egestion.

The process of taking food into the body is called

8. Digestion is the breakdown of complex components of food into simpler substances.

9. Digestion of food begins in the buccal cavity. Carbohydrate, like starch is digested in buccal cavity. Digestion of protein starts in the stomach.

10. The bile secreted from the liver, pancreatic juice from the pancreas and digestive juice from intestinal wall of small intestine complete the digestion of all components of food in the small intestine.

11. The digested food now passes into the blood vessels in the wall of the intestine. This process is called absorption.

12. The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body. This is called

13. The removal of faecal matter through the anus time to time is called

14. Grass-eating animals quickly swallow grass which gets stored in the This partially digested food is called cud. This later returns to the mouth of animals in small lumps, and they chew it. This is called rumination and these animals are known as ruminants.

15. Amoeba ingests its food with the help of finger-like projections, called The food is digested in the food vacuole.

Class 7 Science Chapter 2 Notes Important Terms

Absorption: The passage of the digested food into the blood vessels in the wall of intestine is called absorption.

Amino acid: It is the basic building block of proteins.

Amoeba: It is a single-celled microscopic organism found in pond water.

Assimilation: It is the process in which the absorbed food is used for producing complex substances required by the body.

Bile: Bile juice is a kind of juice secreted by the liver.

Buccal cavity: The cavity of mouth, with all its internal parts like cheeks, teeth, tongue and salivary glands, is called buccal cavity.

Canines: These are two teeth one on each side of the incisors, which help in tearing the food materials.

Cellulose: It is a type of carbohydrate which is present chiefly in all plant tissues and fibres.

Digestion: The breakdown of complex components of food into simpler substances is called digestion.

Egestion: The removal of faeces through the anus from time to time is called egestion.

Fatty acid: It is an organic compound consisting of a long hydrocarbon chain and a terminal carboxylic acid.

Food vacuole: A membrane-bound vacuole (as in an Amoeba) in which ingested food is digested.

Gall bladder: It is a pear-shaped sac, which stores bile juice, and is attached to the undersurface of the right lobe of liver.

Glycerol: It is a colourless, sweet-tasting, viscous liquid, formed as a byproduct when fat is broken down.

Incisors: The front four teeth in each jaw adopted for cutting are called incisors.

Ingestion: The process of intake of food inside the mouth cavity is called ingestion.

Liver: It is a reddish-brown gland located on the upper right side of the abdomen. It secretes bile juice which helps in the digestion of fat.

Milk teeth: The first set of twenty teeth that appears by the age of two is called the set of milk teeth.

Molar: There are six teeth, three on each side of the jaw and just behind the premolars which help in grinding the food materials.

Permanent teeth: Milk teeth are replaced by a set of new teeth, which are thirty two in number, and are called permanent teeth.

Oesophagus: Oesophagus, or food pipe, is a tube-like structure that connect the mouth to the stomach.

Pancreas: It is a large cream-coloured gland located just below the stomach.

Premolar: There are four teeth, two on each side of the jaw which help in crushing the chewed food.

Pseudopodia: One or more finger-like projections in Amoeba which help in movement and ingestion of food is called pseudopodia.

Rumen: Rumen is the first stomach in grass-eating animals, which receives food or cud from the oesophagus immediately after being swallowed.

Ruminant: Animal, that digest food by the process of rumination is called a ruminant.

Rumination: A process by which partially digested food by ruminants returns to their mouth and are again chewed properly, is called rumination.

Salivary glands: Salivary glands are a pair of small and branched structures situated in the mouth cavity. They secrete saliva.

Villi: The inner walls of the small intestine have thousands of finger-like outgrowths called villi.

Saliva: It is a secretion from salivary gland which contains starch splitting enzyme, amylase, for breaking starch into sugar.

On this page, you will find Nutrition in Plants Class 7 Notes Science Chapter 1 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 1 Nutrition in Plants will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 1 Notes Nutrition in Plants

Nutrition in Plants Class 7 Notes Understanding the Lesson

1. Vitamins, carbohydrates, proteins, fats and minerals are the components of food. These components of food are necessary for our body and are called nutrients.

2. The process of procuring and utilization of food by the body is called nutrition.

3. The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic nutrition.

4. The organisms which cannot make their food and depend on others for their food are called heterotrophs and this type of nutrition is called heterotrophic nutrition.

5. Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. These pores are surrounded by ‘guard cells’ such pores are called stomata.

6. The leaves have a green pigment and they are known as chlorophyll.

7. Plants use sunlight, carbon dioxide and water in presence of chlorophyll to synthesise their food. This process is known as photosynthesis.

8. The sun is the ultimate source of energy for all living organisms.

9. The bodies of living organisms are made of tiny units which are called cells.

10. The organisms either plants or animals that derive nutrients from another organisms are known as parasites. For example, Cuscuta, lice, etc.

11. The organisms which provide nutrients to another organisms without being benefitted are known as hosts.

12. The type of plants which trap insects and digest them by producing digestive juices are called insectivorous plants. For example, pitcher plant, sundew, venus fly trap, etc.

13. The mode of nutrition in which organisms take in nutrients in form of solution from dead and decaying matter is called saprophytic nutrition.

14. Plants which use saprophytic mode of nutrition are called saprotrophs.

15. The organisms which live together and share shelter and nutrients are said to be in symbiotic relationship. For example, certain fungi live in the roots of trees.

Class 7 Science Chapter 1 Notes Important Terms

Autotrophic: It is the mode of nutrition in which organisms prepare its own food by using sunlight, air and other essential substances.

Chlorophyll: Chlorophyll is a green pigment present in leaves which absorb solar energy from sunlight, and enables the plant to prepare their food through the process of photosynthesis.

Heterotrophs: The organisms which cannot prepare their food and depends on other organisms for their food are known as heterotrophs.

Host: A plant or an animal which support other organisms by giving food, shelter, etc., is known as host.

Insectivorous: The plant or animal which eat insect for their survival is known as insectivorous.

Nutrients: Vitamins, carbohydrates, proteins, fats and minerals are the components of food. These components of food are essential for our body and are called nutrients.

Parasite: The organism which depends on other organisms for deriving nutrients and their survival is known as parasite.

Photosynthesis: The process by which plants prepare their own food in the presence of sunlight, water, carbon dioxide and chlorophyll is called photosynthesis.

Saprotrophs: Organisms which take their nutrients from dead and decaying matter are called saprotrophs.

Saprotrophic: The mode of nutrition in which an organism take its food from dead and decaying matter is known as saprotrophic mode of nutrition.

Stomata: The tiny pores which are present on the surface of the leaves are called stomata.

In this page, we are providing Wastewater Story Class 7 Extra Questions and Answers Science Chapter 18 pdf download. NCERT Extra Questions for Class 7 Science Chapter 18 Wastewater Story with Answers will help to score more marks in your CBSE Board Exams.

Class 7 Science Chapter 18 Extra Questions and Answers Wastewater Story

Extra Questions for Class 7 Science Chapter 18 Wastewater Story with Answers Solutions

Wastewater Story Class 7 Extra Questions Very Short Answer Type

Question 1.
Define pollutants.
Answer:
The harmful substances which contaminate soil, air and water, etc., are called pollutants.

Question 2.
Name three sources of water.
Answer:

• Lakes
• Ponds
• Wells

Question 3.
Why can’t sea water be used for drinking purpose?
Answer:
Sea water cannot be used for drinking purpose because it contains a big amount of salt that can cause severe water loss and vomiting when consumed.

Question 4.
Why is the bleaching powder mixed with water?
Answer:
Bleaching powder is mixed with water to kill harmful bacteria present in it and make it safe for drinking purposes.

Question 5.
What do you mean by sanitation?
Answer:
Sanitation is the proper disposal of sewage and garbage away from houses and surrounding areas.

Question 6.
Give examples of onsite sewage disposal system.
Answer:
Composting pits, chemical toilets, septic tanks, etc.

Question 7.
Write the full form of WWTP.
Answer:
Waste Water Treatment Plant.

Question 8.
What is meant by chlorination?
Answer:
Chlorination is the process of adding bleaching powder in water to make it safe for drinking.

Question 9.
Give examples of some contaminants present in sewage.
Answer:
Rags, oil, human as well as animal excreta, industrial wastes, etc.

Question 10.
Give examples of some water-borne diseases.
Answer:
Cholera, meningitis, dysentery, typhoid, polio, etc.

Question 11.
Name the type of microbes present in sewage that causes diseases like typhoid and cholera.
Answer:
Bacteria

Question 12.
Name two things that can be made from sludge extracted during treatment of sewage.
Answer:

• Manure
• Biogas

Question 15.
What is scum?
Answer:
Floating dirt or froth on the surface of wastewater is called scum.

Wastewater Story Class 7 Extra Questions Short Answer Type

Question 1.
What is meant by sewerage?
Answer:
Sewerage is a network of big and small pipes called sewage placed under the ground. It can be considered as a transport system that carries wastewater from the point where it is produced to the point of disposal.

Question 2.
Define potable water. Write any two characteristics of potable water.
Answer:
Water that is fit for drinking is called potable water. Its characteristics are following:

• It is odourless and colourless.
• It is transparent.
• It is free from germs and harmful chemicals.

Question 3.
What is clarified water. What can it be used for?
Answer:
Clarified water is the water we get from bar screening, sedimentation, aeration and skimming of the wastewater. It can be used for watering plants, flushing toilets and cleaning public places.

Question 4.
List some sources of water pollution.
Answer:

1. Discharge of sewage
2. Agricultural wastes
3. Domestic wastes
4. Industrial wastes

Question 5.
What should be done to wastewater?
Answer:
Wastewater should not be wasted. It must be cleaned up by removing pollutants.

Question 6.
How do bar screen, and grit and sand removal tank help in cleaning of water?
Answer:
Bar screen removes large objects like rags, cans, plastic packets, etc., from sewage. In grit and sand removal tank heavy solid impurities like pebbles, etc., are removed by sedimentation process.

Question 7.
How does water get polluted?
Answer:
Water is used for numerous purpose in homes, industries, agriculture, etc. It gets polluted when it is used for dying, bathing, flushing toilets, etc. During these activities; many unwanted chemicals, organic and inorganic substances get mixed with water. This pollutes water.

Question 8.
Write one word for the following:
(a) The settled solids that are removed in wastewater treatment with a scraper.
(b) Water from kitchen used for washing dishes.
(c) Wastewater released from homes, industries, hospitals and other public buildings.
Answer:
(a) sludge
(b) wastewater
(c) sewage

Wastewater Story Class 7 Extra Questions Long Answer Type

Question 1.
What is function of a septic tank?
Answer:
A septic tank consists of a big covered underground tank made of concrete. It also consists of an inlet pipe at one end and an outlet pipe at the other end. The toilet seat is connected to the inlet pipe. The human excreta enters the tank through the inlet pipe, the solid portion of the excreta gets collected at the bottom of the tank in the form of sludge whereas the liquid waste gets collected above it.

The anaerobic bacteria break down most of the solid wastes owing to which the volume of solid reduces to a great extent. The liquid waste is also decomposed by the bacteria. Bacteria deposit the digested solid at the bottom of the septic tank. The excess water goes out of the septic tank through the outlet pipe and is absorbed by the soil.

Question 2.
What is vermi-processing toilet? Explain.
Answer:
Vermi-processing toilet is a type of toilet in which the human excreta is processed by earthworms. This has been tested in India. It has proved to be a low-water use, nobel method for disposal of human ex¬creta. Toilet is operated in a very simple and hygienic way. The human excreta is converted into vermi- cakes. Hence it becomes a resource much needed for the soil.

Question 3.
List various steps involved in waste water treatment.
Answer:
Treatment of wastewater involves physical, chemical, and biological processes, which remove physical, chemical and biological matter that contaminates the wastewater.

1. First wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removed.
2. Water than goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow sand, grit and pebbles to settle down.
3. The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This settled solid is called sludge.
4. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water.
5. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.
6. Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps and other unwanted matter still remaining in clarified water.
7. After several hours, the suspended microbes settle at the bottom of the tank as activated sludge. The water is then removed from the top.
8. The activated sludge contains about 97% water which is removed by sand drying beds or machines. Dried sludge is used as manure, returning organic matter and nutrients to the soil.
9. The treated water now, has a very low level of organic material and suspended matter. It is discharged into a sea, or river or into the ground.
10. Nature cleans it up further. Sometimes it may be necessary to disinfect water with chemicals like chlorine and ozone before releasing it into the distribution system.

Question 4.
Name various components of sewage.
Answer:
Sewage is a complex mixture containing suspended solids, organic and inorganic impurities, nutrients, saprotrophic and disease-causing bacteria and other microbes.

1. Organic impurities: Human faeces, animal waste, oil, urea (urine), pesticides, herbicides, fruit and vegetable waste, etc.
2. Inorganic impurities: Nitrates, phosphates, metals.
3. Nutrients: Phosphorus and nitrogen.
4. Bacteria: Such as which causes cholera, typhoid, dysentery, etc.

Question 5.
How can we minimise the discharge of pollutants at their source?
Answer:
To minimise or eliminate waste and pollutants at their source we must see what we are releasing down the drain.

1. Cooking oil and fats should not be thrown down the drain. They can harden and block the pipes. In an open drain the fats clog the soil pores reducing its effectiveness in filtering water. We should throw oil and fats in the dustbin.
2. Chemicals like paints, solvents, insecticides, motor oil, medicines may kill microbes that help purify water. So we should not throw them down the drain.
3. Used tea leaves, solid food remains, soft toys, cotton, sanitary towels, etc. should also be thrown in the dustbin.
4. These wastes choke the drains. They do not allow free flow of oxygen. This hampers the degradation process.

Wastewater Story Class 7 Extra Questions HOTS

Question 1.
What is effluent?
Answer:
Effluent is a liquid waste or sewage discharged into a river or the sea.

Question 2.
State beneficial activity of microbes in sewage disposal.
Answer:
Microbes present in sewage water help to digest organic matter present in it and thus purifying water aerobically. Anaerobic microbes help in digestion of sludge into useful manures.

Question 3.
What are the common symptoms of water-borne diseases?
Answer:
Common symptoms of water-borne diseases are vomiting, stomachache, diarrhoea, fever, loss of appetite, etc.

Question 4.
How the terms sewage, sewers and sewerage are interlinked to each other?
Answer:
Sewage is the wastewater coming from houses and other places. Sewers are the pipes which carry sewage whereas network of sewers, manholes, pumping stations, drains, etc. form sewerage.

Question 5.
Why should we not throw
(a) Cooking oils and fats down the drains?
(b) Cotton buds, napkins and nappies down the toilets?
Answer:
(a) Cooking oils and fats can harden and block the pipes.
(b) Cotton buds, napkins and nappies are flushed with difficulties and are not easily degradable. They can block the drains.

Wastewater Story Class 7 Extra Questions Value Based (VBQs)

Question 1.
Sonam never mind to dispose her household waste like tea leaves, vegetable peels and even remaining foods from plates into the sink. Sometimes she even flush the waste from brooming or sweeping into the toilets.
(a) What will be the affects of Sonam’s practices on the process of wastewater treatment?
(b) How Sonam’s practice of throwing waste into sink and toilets will affect the sewer system?
(c) What value of Sonam is shown here?
(d) Being an active citizen, what would you like to suggest Sonam?

Answer:
(a) She is adding to the load of WWTP, by increasing waste and pollutants at their source.
(b) Throwing of tea leaves, vegetable peels and food remains may clog the sewer pipes. Waste from brooming and sweeping may also contain some non-biodegradable wastes which can choke drains or hamper in degradation processes.
(c) Sonam is impulsive, irresponsible and eco-unfriendly.
(d) Sonam must throw all the solid waste into a dustbin instead of throwing directly into sink or toilet. She must minimise or eliminate waste and pollutants at their source to decrease the load on WWTP.