Balbharti Maharashtra State Board Class 7 Science Solutions Chapter 3 Properties of Natural Resources Notes, Textbook Exercise Important Questions and Answers.
Class 7 Science Chapter 3 Properties of Natural Resources Textbook Questions and Answers
Fill in the blanks with the appropriate term.
Question 1.
The capacity of air to hold moisture depends upon the …………… of the air.
Answer:
temperature
Question 2.
Water does not have a …………… but has definite ………… and ………. .
Answer:
shape, volume, mass
Question 3.
While freezing, the ………….. of water is lowered.
Answer:
density
Question 4.
…………….. soil has pH 7.
Answer:
neutral
2. Why is the said that –
Question a.
Air is a homogeneous mixture of various gases.
Answer:
Question b.
Water is a universal solvent.
Answer:
Question c.
There is no alternative to water for cleaning purposes.
Answer:
Water is a universal solvent. It dissolves more substances than any other liquid so there is no alternative to water for cleaning purposes.
3. What will happen if……
Question a.
The amount of water vapour in the air increases.
Answer:
We feel the dampness or the humidity.
Question b.
Only one crop is grown repeatedly in the soil.
Answer:
The fertility of the soil decreases.
4. With whom should I pair up?
Question a.
| Column ‘A’ | Column ‘B’ |
| 1. Air | a. Excretion |
| 2. Water | b. Scattering of light |
| 3. Soil | c. Plasticity |
Answer:
| Column ‘A’ | Column ‘B’ |
| 1. Air | b. Scattering of light |
| 2. Water | a. Excretion |
| 3. Soil | c. Plasticity |
5. State whether the following statements are true or false.
Question a.
Sandy soil has low capacity for holding water.
Answer:
True
Question b.
Sea water is a bad conductor of electricity.
Answer:
False. Sea water is a good conductor of electricity
Question c.
The substance in which a solute dissolves is called a solvent.
Answer:
True
Question d.
The pressure exerted by air is called atmospheric pressure.
Answer:
True
6. Explain the picture in your own words.
Question a.
Explain the picture in your own words.
Answer:
7. Write answers to the following questions in your own words.
Question a.
How is light scattered by the air?
Answer:
Air is a mixture of very fine particles of some gases, dust, smoke and moisture. When rays of light fall on these minute particles, the particles spread the light in all the directions. This natural phenomenon is called scattering of light.
Question b
Explain the various properties of water.
Answer:
Various properties of water are as follows:
Question c.
Why is the density of seawater is more than that of rainwater?
Answer:
Seawater has many minerals dissolved in it as compared to rainwater. So due to more dissolved salts, density of seawater is more than that of rainwater.
Question d.
What is the importance of good soil structure?
Answer:
The fertility of soil depends upon soil structure. So importance of good soil structure is as follows: (a) Roots get sufficient supply of oxygen, (b) Water drainage is good therefore the roots of plants grow well.
Question e.
What are the various uses of soil?
Answer:
The uses of soil are as follows:
Plant conservation: To help plants grow. Water conservation: Soil holds water. As a result, by means of bunds and lakes, we can get water for use throughout the year.
Plasticity: (a) Soil can be given any required shape. This property of soil is called plasticity, (b) Because of its plasticity, we can use it to make articles of a variety of shapes, (c) These articles can be baked to make them hard, (d) Water storage earthen pots, earthen lamps, idols, bricks etc. are articles made from soil.
Question f.
What is the need and importance of soil testing from the point of view of farmers?
Answer:
Question g.
What is the importance of air in transmission of sound?
Answer:
Question h.
Why should a glass bottle completely filled with water never be kept in a freezer?
Answer:
Project:
Question a.
Visit a soil testing laboratory. Learn the process of soil testing and share it with others.
Class 7 Science Chapter 3 Properties of Natural Resources Important Questions and Answers
Fill in the blanks with the appropriate term.
Question 1.
Air is a …………… of gases.
Answer:
mixture
Question 2.
Atmospheric pressure is the …………… in all the directions.
Answer:
same
Question 3.
…………… is used to measure atmospheric pressure.
Answer:
Barometer
Question 4.
As we go higher the sea level and the atmospheric pressure …………… .
Answer:
decreases
Question 5.
Pressure of air …………… when its velocity …………… .
Answer:
increases, decreases
Question 6.
…………… an effect of the difference in air pressure.
Answer:
Wind
Question 7.
The level of …………… in the air is determined by its capacity to hold water vapour.
Answer:
humidity
Question 8.
When the temperature of air is low, its capacity to hold the vapour is …………… .
Answer:
less
Question 9.
Air is useful as a …………… for the transmission of sound.
Answer:
medium
Question 10.
Water is a …………… substance.
Answer:
fluid
Question 11.
Ice is …………… than water.
Answer:
lighter
Question 12.
Density of ice is …………… than that of water.
Answer:
less
Question 13.
The space occupied by a substance is its …………… .
Answer:
volume
Question 14.
The storage of matter in a substance is its …………… .
Answer:
mass
Question 15.
The density of water is maximum at …………… °C.
Answer:
4°C
Question 16.
The substance in which the solute dissolves is called …………… .
Answer:
solvent
Question 17.
The particles of sandy soil are made of the mineral called …………… .
Answer:
silicon dioxide (quartz)
Question 18.
…………… soil has a highest water holding capacity.
Answer:
clay
Question 19.
…………… soil is red in colour.
Answer:
Terracotta
Question 20.
…………… soil is used in cosmetics.
Answer:
Multani
Question 21.
…………… is celebrated as World Soil Day.
Answer:
5th December
Question 22.
The excess of water vapour during the night or dawn is transformed into ………….. .
Answer:
dew
Question 23.
Under ordinary conditions atmospheric pressure at sea level is …………… Newtons per square mater.
Answer:
101400
Question 24.
Swedish Scientist …………… put forth the important principle that the pressure of air decreases when its velocity increases.
Answer:
Daniel Bernoulli
Question 25.
When rays of light fall on fine particles of air, the particles spread light in all the directions, this is called …………… of light.
Answer:
Scattering
Question 26.
…………… soil is easy to plough but less fertile.
Answer:
Sandy
Say whether true or false, correct and rewrite the false statements.
Question 1.
Terracotta soil is white in colour.
Answer:
False. Terracotta soil is red in colour
Question 2.
The fertility of soil depends upon soil structure.
Answer:
True
Question 3.
Multani soil is used to make statues and idols.
Answer:
False. Shadu soil is used to make statues and idols
Question 4.
Clay soil has the maximum proportion of small particles.
Answer:
True
Question 5.
Silt soil is not as ploughable as sandy soil.
Answer:
True
Question 6.
The colour of soil near land surface is darker than the colour of the lower layers.
Answer:
True
Question 7.
Kerosene is a universal solvent.
Answer:
False. Water is an universal solvent
Question 8.
The density of substance is the inter-relation between the volume and mass of a substance.
Answer:
True
Question 9.
Water is lighter than ice.
Answer:
False. Ice is lighter than water
Question 10.
Rotation of crops decreases the fertility of the soil.
Answer:
False. Rotation of crop increases the fertility of the soil.
Match the columns:
Question 1.
| Column ‘A’ | Column ‘B’ |
| 1. Concept of pH | a. pH higher than 7.5 |
| 2. Acidic Soil | b. pH 6.5 – 7.5 |
| 3. Neutral Soil | c. pH less than 6.5 |
| 4. Alkaline Soil | d. Sorensen |
Answer:
| Column ‘A’ | Column ‘B’ |
| 1. Concept of pH | d. Sorensen |
| 2. Acidic Soil | c. pH less than 6.5 |
| 3. Neutral Soil | b. pH 6.5 – 7.5 |
| 4. Alkaline Soil | a. pH higher than 7.5 |
Write short answers.
Question 1.
What is atmospheric pressure?
Answer:
The molecules of the gases in the air are in constant motion. When these molecules strike a body, they create pressure on that body. This pressure of air is called atmospheric pressure.
Question 2.
What is Bernoulli’s principle?
Answer:
Bernoulli’s principle is that the pressure of air ‘ decreases when its velocity increases while the pressure of air increases when its velocity decreases.
Give scientific reasons.
Question 1.
When the piston of a syringe is released, it is immediately pushed in.
Answer:
Question 2.
Water droplets are seen on the outer surface of a glass having ice cubes in it.
Answer:
Question 3.
Early morning dew drops are found on the grass.
Answer:
Question 4.
During the afternoon we feel that the air is dry.
Answer:
Question 5.
Earth’s surface remains warm and suitable for the living world on the earth.
Answer:
Question 6.
We can hear the whistle of a distant train clearly early in the morning in winter.
Answer:
Question 7.
Ice floats on water.
Answer:
Question 8.
In cold countries aquatic animals remain alive even after the rivers or lakes freeze in water.
Answer:
1. Due to anomalous behaviour of water, in cold countries when water gets cool and turn to ice, its volume increases, so its density decreases
2. Due to less density ice floats on water.
3. (a) Ice is a bad conductor of heat and electricity, (b) It doesn’t allow outside heat to go from the ice to water so water temperature below the ice doesn’t change, (c) It remains as water so aquatic animals remain alive even after the rivers or lakes freeze in winter.
Question 9.
It is easier to swim in the sea than in a well or a lake.
Answer:
Question 10.
Sandy soil is less fertile.
Answer:
Question 11.
China clay is used for making crockery.
Answer:
China clay is used for making crockery because on heating, this clay acquires a glaze and hardness. It can be moulded into any shape and being a bad conductor of heat, it is easy to handle.
Answer the following:
Question 1.
Write the properties of air.
Answer:
Question 2.
Name the tests for finding out the characteristic of soil. Describe any one method of it.
Answer:
There are two tests for finding out the characteristics of soil: (1) pH (2) electrical conductivity tests.
1. pH tests: The Danish scientist Sorensen put forth the concept of pH, based on the concentration of hydrogen ions. To determine the pH of soil, a mixture of water and soil in the proportion of 1 : 2 is taken and tested using several indicators.
Accordingly, soil may be found to be one of the following types.
2. By Electrical conductivity tests we come to know how many nutrients are present in the soil.
Question 3.
Write the causes of diminished soil fertility.
Answer:
Following are the causes of diminished soil fertility.
Question 4.
Which crops reduce the fertility of soil and Which crops increase the fertility of soil?
Answer:
Wheat reduces the fertility of soil and leguminous crops like peanut, moong, moth bean, pea, lentil, Bengal gram, soyabean increase the fertility of soil.
Question 5.
Name and explain some useful types of soil.
Answer:
Following are some useful types of soil.
Question 6.
Explain the types of soil on the basis of its texture.
Answer:
There are 3 types of soil on the basis of its texture.
1. Sandy soil: (a) Large particles are high in sandy soil, (b) Water drains rapidly through sandy soil, (c) It is easy to plough this soil, (d) It is less fertile because the particles of sandy soil are made of the mineral called silicon dioxide (quartz), (e) These particles do not dissolve in water and therefore the soil has very little capacity to supply dissolved nutrients.
2. Silt soil: (a) The particles of silt soil are of medium size, (b) Silt soil is not as ploughable as sandy soil but is much more ploughable than clay soil, (c) This soil contains a large proportion of organic materials, (d) Its capacity to supply nutrients is much greater, (e) Silt soil is also called sedimentary soil.
3. Clay soil: (a) The proportion of small particles is maximum, (b) The particles of clay soil feel smooth to touch, (c) Clay soil has a high water holding capacity.
Explain the given picture in your own words.
Question 1.
Answer:
1. The potato will sink in water as potato’s density is more than water.
2. This is the effect of density. The potato will float in salt solution as the density of salt solution is more than potato. The density of the water becomes greater due to the dissolved salt. That is why it is easier to swim in sea than in a well or a lake.
Can you tell?
Answer the following questions.
Question 1.
What change takes place in a balloon on filling air in it?
Answer:
On filling air in balloon, the shape of the balloon changes. Its size increases due to expansion.
Question 2.
Why is it easier to swim in the sea than in a well or a lake?
Answer:
Use your brain power!
Answer the following questions.
Question 1.
What is the effect of increased temperature on the pressure of air?
Answer:
Condition for closed environment:
Question 2.
Dip an uncorked inverted empty bottle in a slanting position into the water in a wide container. What do you observe?
Answer:
Question 3.
In cold countries how do aquatic animals remain alive even after the rivers or lakes freeze in winter.
Answer:
Question 4.
Why is it difficult to plough clay soil?
Answer:
It is difficult to plough clay soil because in clay soil the proportion of small particles is maximum. The particles of clay soil feel smooth to touch and has high water holding capacity, making it very difficult to penetrate through it.
Question 5.
Why is it easy to plough sandy soil?
Answer:
Question 6.
What is the water holding capacity of silt soil?
Answer:
Silt occurs as a deposit in riverbeds. The size of silt particles is between those of sand and clay. This soil also has humus in it which makes it the best soil to hold the right amount of water.
Question 7.
Which soil is suitable for cultivation? Why?
Answer:
The silt soil is suitable for cultivation.