CBSE Class 7

On this page, you will find Soil Class 7 Notes Science Chapter 9 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 9 Soil will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 9 Notes Soil

Soil Class 7 Notes Understanding the Lesson

1. Soil is one of the most important natural resources for supporting life on the earth.

2. The rotting dead matter in the soil is called humus.

3. Soil is formed by breaking down of rocks by the action of wind, water and climate and this process is called weathering.

4. A vertical section through different layers of the soil is called the soil profile. Each layer differs in feel (texture), colour, depth and chemical composition. These layers are referred to as horizons.

5. A-horizon is the uppermost layer. It is also known as the topsoil. This layer is rich in humus and minerals. It is dark, soft and porous. This provides shelter to many living organisms and roots of small plants are embedded entirely in the topsoil.

6. B-horizon is the layer which is just below the A-horizon and is known as the sub-soil. This layer is rich in minerals and is normally hard and compact.

7. C-horizon is the layer which is just below the B-horizon. This layer has partially weathered rock with a lot of cracks and a long narrow opening.

8. Bedrock is the bottom-most layer in soil profile and is known as the bedrock. This is the type of layer which is full of hard rock.

9. The mixture of rock particles and humus is called the soil. Soil can be classified into three main types based on the proportion of soil particles they are composed of. They are

• Sandy soil
• Clayey soil and
• Loamy soil.

10. Sandy soil contains a larger proportion of big particles. It is well aerated and water drains quickly in this type of soil.

11. Silt soil contain soil particles of size in between sand and clay. Silt feels smooth and powdery.

12. Clayey soil contains a larger proportion of fine particles. It has little air spaces between the particles. Water does not drain quickly in this type of soil.

13. Loamy soil contains almost equal proportion of large and fine particles. Loamy soil is a mixture of sand, clay and silt. It also has a lot of humus in it.

14. Following are the properties of soil:

• Soil colour
• Soil texture
• Water-holding capacity
• Percolation rate

15. Soil contains water in the form of moisture.
16. Different soils have different water holding capacity. It is highest in clayey soil and least in sandy soil.
17. Percolation rate of water is different in different types of soil. It is highest in sandy soil and least in the clayey soil.
18. The factors that affect soil are wind, rainfall, temperature, light and humidity. These factors also affect the soil profile and bring changes in the soil structure.
19. The removal of topsoil by the action of water and wind is called soil erosion. Following are some factors which lead to soil erosion:

• Large scale cutting of trees-deforestation.
• Overgrazing in forests.
• Deep ploughing and forests fires also lead to soil erosion.

20. Planting more and more trees or afforestation helps in preventing soil erosion as plant roots bind the soil.
21. Preventing overgrazing, doing terrace farming and planting windbreaks can also help in controlling soil erosion.

Class 7 Science Chapter 9 Notes Important Terms

Clayey: It is a type of soil which have large proportion of fine particles. It has little air space between the particles. Water does not drain quickly in these type of soil.

Humus: A dark-brown or black organic component of soil, formed by the decomposition of leaves and other plant material by soil microorganisms.

Loamy: This type of soil contains almost equal proportions of large and fine particles. It is a mixture of sand, clay and silt.

Moisture: Soil contains water in the form of moisture. Moisture content of a soil depends upon its type and source.

Percolation: Percolation means the movement of water through the soil. It is the rate at which water flows or trickles through porous soil.

Sandy: It is a type of soil which contains a larger proportion of big particles. It is gritty with lot of air spaces between its particles. It is well aerated. Water drains quickly in this type of soil.

Water retention: It is the property of soil to hold a given amount of water which can be used by the crop.

On this page, you will find Winds, Storms and Cyclones Class 7 Notes Science Chapter 8 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 8 Winds, Storms and Cyclones will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 8 Notes Winds, Storms and Cyclones

Winds, Storms and Cyclones Class 7 Notes Understanding the Lesson

1. The moving air is called wind.

2. Air exerts pressure on all object. This is called air pressure.

3. Increased wind speed is accompanied by a reduced air pressure.

4. Air moves from a higher pressure region to a lower one. The greater the difference in pressure, the faster the air moves.

5. On heating the air expands and occupies more space. Hence, it becomes lighter. The warm air is, there­fore, lighter than cold air. That is the reason that the smoke goes up.

6. At a place, where warm air rises, the air pressure is reduced and the cooler air moves to   that place.

7. Wind currents are generated due to uneven heating on the earth. High speed winds are accompanied by reduced pressure.

8. Regions nearer to the equator get maximum heat from the sun. The air in these regions gets warm. The warm air rises, and the cooler air from the region in the 0-30 degrees latitude belt on either side of the equator moves in.

9. At the poles, the air is colder than that at latitudes about 60 degrees. The warm air at these latitudes rises up and the cold wind from the polar regions rushes in, to take its place. In this way, wind circulation is set up from the poles to the warmer latitudes.

10. Due to uneven heating of land and water, in summer, the land near the equator warms up faster and most of the time the temperature of the land is higher than that of water in this oceans.

11. In winter, the direction of the wind is from the land to the ocean.

12. The wind from the ocean carry water and bring rain. It is a part of the water cycle.

13. The monsoon winds carry water and it rains.

14. The winds blow from the oceans towards the land in summer. These are called monsoon winds.

15. There are certain situations, in nature itself, that can sometimes create disasters like thunderstorms and cyclones. They pose threat to humans, animals and plant life.

16. The strong upward rising winds produced by the rising temperature carry water droplets upward where they freeze and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that is called

17. The chain of events of thunderstorm ends with the formation of a very low-pressure system with very high-speed winds revolving around it. It is this weather condition that we call a

18. A cyclone is known by different names in different parts of the world such as ‘hurricane’ in the American continent, ‘typhoon’ in Philippines and Japan, etc.

19. Tornado is a dark funnel-shaped cloud that reaches from the sky to the ground.

20. Self-help is the best help. Therefore it is better to plan in advance and be ready with defence against any approaching cyclone.

Class 7 Science Chapter 8 Notes Important Terms

Anemometer: The instrument that measures the speed of wind is called an anemometer.

Cyclone: A violent storm with wind speed of 120 to 200 km/hr is called a cyclone. It is accompanied by strong winds and heavy rain. It is a very low-pressure system with a very high speed winds revolving around.

Hurricane: A cyclone is known as hurricane in the American continent.

Lightning: A flash of bright light produced by an electric discharge between clouds or between clouds and the ground is called lightning. It occurs when two clouds with unlike charges approach each other.

Low pressure: A condition of the atmosphere in which the pressure is below average. It is also caused when warm air rises up.

Monsoon winds: The wind from the oceans carry water and bring rain. These winds are called monsoon winds.

Pressure: Pressure is exerted by air around us.

Thunderstorms: The rising temperatures produce strong upward rising winds. These winds carry water droplets upwards, where they freeze and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that is called thunderstorm.

Tornado: A tornado is a dark funnel-shaped cloud that reaches from the sky to the ground. It may form within a cyclone.

Typhoon: A cyclone is called a typhoon in Philippines and Japan.

Wind flow pattern: Winds flow from oceans towards the land in summer and from land to oceans in winter.

On this page, you will find Weather, Climate and Adaptations of Animals to Climate Class 7 Notes Science Chapter 7 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 7 Weather, Climate and Adaptations of Animals to Climte will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 7 Notes Weather, Climate and Adaptations of Animals to Climate

Weather, Climate and Adaptations of Animals to Climate Class 7 Notes Understanding the Lesson

1. The day-to-day condition of the atmosphere at a place with respect to the temperature, humidity, rainfall, wind speed, etc., is called the weather at that place.

2. The temperature, humidity and other factors are called elements of the weather.

3. To record the maximum and minimum temperatures during day, there are special thermometers, called maximum and minimum thermometers.

4. The maximum temperature of the day occurs generally in the afternoon while the minimum occurs in the early morning.

5. All the changes in weather are driven by the sun.

6. The average weather pattern takes over a long time, say 25 years, is called the climate of the place.

7. Mean temperature for a given month is found by first finding the average of the temperatures recorded during the month then calculating the average of such average temperatures over many years.

8. The annual record of long-term average temperature and rainfall at a particular place is called climate chart.

9. The tropical and the polar regions are the two regions of the earth, which have severe climatic conditions.

10. Animals are adapted to survive in the conditions in which they live.

11. Animals in the polar region are adapted to the extremely cold climate by having some special characteris­tics such as strong sense of smell, a layer of fat under the skin, white fur, wide and large paws for walking and swimming.

12. Some birds migrate to escape the harsh, cold conditions.

13. Some adaptations of animals living in tropical rainforests include living on the trees, development of strong tails, long and large beaks, sensitive hearing, sharp eyesight, ability to camouflage, etc.

Class 7 Science Chapter 7 Notes Important Terms

Adaptation: The presence of specific features and habits which enable a plant or animal to live in a particular habitat is called adaptation.

Climate: The average weather pattern taken over a long time, say 25 years, is called the climate of the place.

Elements of weather: Temperature, humidity, rainfall, wind speed and other factors are called elements of weather.

Humidity: The amount of moisture in the air is called humidity.

Maximum temperature: The maximum temperature of the day occurs generally in the afternoon.

Migration: The means of escaping from the harsh and cold conditions, if adaptation is not possible then it is known as migration.

Minimum temperature: The minimum temperature of the day occurs generally in the early morning.

Polar region: The region which is very cold throughout the year with -37°C temperature is known as polar region.

Tropical rainforest: These are found in tropical regio-0n where hot and wet climate is found.

Tropical region: The region which generally have hot and wet climate because of its location around the equator is called tropical region.

Weather: The day-to-day condition of the atmosphere at a place with respect to their elements, like tem­perature, humidity, rainfall, wind speed, etc., is called as weather.

On this page, you will find Physical and Chemical Changes Class 7 Notes Science Chapter 6 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 6 Physical and Chemical Changes will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 6 Notes Physical and Chemical Changes

Physical and Chemical Changes Class 7 Notes Understanding the Lesson

1. The changes around us can be broadly classified as – physical and chemical change.

2. Properties like shape, size, colour, state, etc., of a substance are called its physical properties.

3. A change in which a substance experiences a change in its physical properties is known as physical change.

4. Physical change is generally reversible.

5. A change in which one or more new substances are formed is called a chemical change.

6. Chemical change is generally irreversible.

7. The process of formation of red or orange coating on the surface of iron when exposed to air and moisture, consisting chiefly of ferric hydroxide and ferric oxide, is called

8. The process of rusting can be represented by the following equation:
Iron (Fe) + Oxygen (0₂, from the air) + Water (H₂0) ➝ Rust (Fe₂0₃, Iron oxide)

9. The presence of both oxygen and water (or water vapour) is essential for rusting.

10. The process of depositing a layer of zinc metal on iron is known as It protects iron from rusting.

11. Crystallization is the process of separating pure crystals of a substance from its supersaturated solution on cooling.

Class 7 Science Chapter 6 Notes Important Terms

Chemical change: A change in which the chemical properties of a substance get changed, and new sub­stances are formed is called a chemical change.

Chemical reaction: A chemical change is also known as chemical reaction. In fact, the process involving a chemical change is accompanied by a chemical reaction.

Crystallization: The process of separating pure crystals of a substance from its super-saturated solution is known as crystallization.

Galvanization: The process of depositing a layer of zinc on iron metal is called galvanization.

Physical change: A change in which a substance undergoes a change in its physical properties is called a physical change.

Rusting: A process in which a layer of rust covers the surface of iron is called rusting.

On this page, you will find Acids, Bases and Salts Class 7 Notes Science Chapter 5 Pdf free download. CBSE NCERT Class 7 Science Notes Chapter 5 Acids, Bases and Salts will seemingly help them to revise the important concepts in less time.

CBSE Class 7 Science Chapter 5 Notes Acids, Bases and Salts

Acids, Bases and Salts Class 7 Notes Understanding the Lesson

1. Any of the various water-soluble compounds having sour taste and capable of turning litmus red and reacting with a base to form a salt and water are called acids; e. g. curd, lemon juice, orange juice, vinegar, etc. The chemical nature of these substances are said to be acidic. The acids in these substances are natural acids.

2. Any of various water-soluble compounds having bitter taste and capable of turning litmus blue and reacting with an acid to form a salt and water are called bases. They feel soapy when touched. Bases include oxides and hydroxides of metals and ammonia. The nature of such substances is said to be basic; g., calcium hydroxide, ammonium hydroxide, magnesium oxide, etc.

3. Some special type of substances are used to test the acidic or basic nature of a substance. These substances are known as indicators.

4. Indicators change their colour when added to a solution containing an acidic or a basic substance. There are some naturally occurring indicators such as turmeric, litmus, china rose petals (Gudhal), etc.

5. The most commonly used natural indicator is litmus which is extracted from lichens.

6. It has a mauve (purple) colour in distilled water. It turns red when added to an acidic solution and blue when added to a basic solution. It is available in the form of a solution, or in the form of strips of paper, i.e., red and blue litmus paper.

7. Turmeric is natural indicator which turns from yellow to red in alkaline (basic) solution.

8. China rose petal solution turns dark pink in acidic solution and green in basic solution. It is also a natural indicator.

9. There are also some substances which are neither basic nor acidic. The solutions (substances) which do not change the colour of either red or blue litmus are called neutral substances or solutions, e. g., distilled water, common salt solution, sugar solution, etc.

10. The reaction between an acid and base is known as neutralisation. Salt and water are produced in this process with the evolution of heat.

Acid + Base ➝ Salt + Water (Heat is evolved)

The following reaction shows neutralization:

11. In neutralisation reaction salt is formed which may be acidic, basic or neutral in nature.

12. Neutralisation reaction is helpful in everyday life. It is used in case of indigestion, ant bite, soil treatment, etc.

Class 7 Science Chapter 5 Notes Important Terms

Acid: Substance that tastes sour and turns litmus red in colour is called acid.

Acidic: The chemical nature of acid substance is said to be acidic.

Base: Substance which is bitter im taste, feel soapy on touching and turns litmus blue is called base.

Basic: The chemical nature of base substance is said to be basic.