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Question
Write answers to the following questions in your own words.
(a) How is light scattered by the air?
(b) Explain the various properties of water.
(c) Why is the density of seawater more than that of rain water?
(d) What is the importance of good soil structure?
(e) What are the various uses of soil?
(f) What is the need and importance of soil testing from the point of view of farmers?
(g) What is the importance of air in transmission of sound?
(h) Why should a glass bottle completely filled with water never be kept in a freezer?
(a) How is light scattered by the air?
(b) Explain the various properties of water.
(c) Why is the density of seawater more than that of rain water?
(d) What is the importance of good soil structure?
(e) What are the various uses of soil?
(f) What is the need and importance of soil testing from the point of view of farmers?
(g) What is the importance of air in transmission of sound?
(h) Why should a glass bottle completely filled with water never be kept in a freezer?
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Solution
a. Scattering is the phenomenon of change in direction of light rays when they travel through Earth's atmosphere. Air is a mixture of gases, somke, dust and very fine particles. As the rays of light fall on these particles, these rays are spread/scattered in all directions. It is a natural phenomenon which is observed on our daily basis.
b. Properties of water:
- Water is a colourless, tasteless, and transparent liquid. It also has no smell.
- Boiling point of pure water is 100°C at 760 mm of Hg pressure. However, boiling point of water increases due to increase in pressure and presence of dissolved impurities.
- Pure water freezes at 0°C at 760 mm of Hg pressure. However, freezing point of water decreases due to increase in pressure and presence of dissolved impurities.
- The state of water changes on heating or cooling. On heating, the state of water changes from liquid state to gaseous state (vapour). Similarly, on cooling, the state of water changes from liquid state to solid state (ice).
- Water is neither acidic nor basic. It is neutral.
- Water is a bad conductor of heat and electricity.
- Water is an universal solvent as it can dissolve many substances in it.
c. Sea water has more density than rain water because it contains salt ions. These salt ions make the seawater heavier, which means the mass of the water increases due to the presence of salt ions. From the relation, density= mass/volume, we can say that as the mass of an object increases, its density also increases simultaneously.
d. Soil stucture basically refers to the type of constituents and the ratio in which they are present in soil. The soil structure is important with respect to the growth of plants and the type of plantation which can occur in a particular area. Good soil structure has advantages like:
- roots get sufficient supple of oxygen
- it has good water drainage nad thus roots grow well
e. The following table represents the various types of soil:
Soil type
Particle type
Properties
Sandy
Large
Loosely packed, with large air spaces. Water soaks into it easily. Thus it is dry, light and airy
Clayey
Fine, small
Tightly packed with no air spaces. This type of soil is heavy and holds more water.
Loamy/silt
A mixture of large and small particles
Holds water, contains humus.
f. Soil testing is a method of determining the constituents of soil. A sample of soil is taken and is tested for its various characteristics for example, ph and electrical conductivity. It is important with respect to agricultural practices as it helps us in determining which crops can be grown in which region. It also gives us a knowledge about the deficient nutrients and this deficiency can then accordingly be dealt with. It is also useful in determining, if additional amounts of fertilizers are required.
g. Air acts as a medium for transmission of sound. When a sound wave passes through air, the particles of air vibrate back and forth, parallel to the direction of the sound wave. Thus, when a sound wave travels in the horizontal direction, then the particles of the medium also vibrate back and forth in the horizontal direction. Sound cannot travel without a medium and thus we cannot listen to sounds in the space because of absence of air.
h. A glass bottle completely filled with water should not be kept in a freezer because the bottle can break and result in damage. We know that water expands after freezing and if a completely water filled glass bottle is placed in freezer, the water would freeze and would expand resulting in the bottle to break.
b. Properties of water:
- Water is a colourless, tasteless, and transparent liquid. It also has no smell.
- Boiling point of pure water is 100°C at 760 mm of Hg pressure. However, boiling point of water increases due to increase in pressure and presence of dissolved impurities.
- Pure water freezes at 0°C at 760 mm of Hg pressure. However, freezing point of water decreases due to increase in pressure and presence of dissolved impurities.
- The state of water changes on heating or cooling. On heating, the state of water changes from liquid state to gaseous state (vapour). Similarly, on cooling, the state of water changes from liquid state to solid state (ice).
- Water is neither acidic nor basic. It is neutral.
- Water is a bad conductor of heat and electricity.
- Water is an universal solvent as it can dissolve many substances in it.
c. Sea water has more density than rain water because it contains salt ions. These salt ions make the seawater heavier, which means the mass of the water increases due to the presence of salt ions. From the relation, density= mass/volume, we can say that as the mass of an object increases, its density also increases simultaneously.
d. Soil stucture basically refers to the type of constituents and the ratio in which they are present in soil. The soil structure is important with respect to the growth of plants and the type of plantation which can occur in a particular area. Good soil structure has advantages like:
- roots get sufficient supple of oxygen
- it has good water drainage nad thus roots grow well
e. The following table represents the various types of soil:
|
Soil type |
Particle type |
Properties |
| Sandy | Large | Loosely packed, with large air spaces. Water soaks into it easily. Thus it is dry, light and airy |
| Clayey |
Fine, small |
Tightly packed with no air spaces. This type of soil is heavy and holds more water. |
| Loamy/silt | A mixture of large and small particles |
Holds water, contains humus. |
f. Soil testing is a method of determining the constituents of soil. A sample of soil is taken and is tested for its various characteristics for example, ph and electrical conductivity. It is important with respect to agricultural practices as it helps us in determining which crops can be grown in which region. It also gives us a knowledge about the deficient nutrients and this deficiency can then accordingly be dealt with. It is also useful in determining, if additional amounts of fertilizers are required.
g. Air acts as a medium for transmission of sound. When a sound wave passes through air, the particles of air vibrate back and forth, parallel to the direction of the sound wave. Thus, when a sound wave travels in the horizontal direction, then the particles of the medium also vibrate back and forth in the horizontal direction. Sound cannot travel without a medium and thus we cannot listen to sounds in the space because of absence of air.
h. A glass bottle completely filled with water should not be kept in a freezer because the bottle can break and result in damage. We know that water expands after freezing and if a completely water filled glass bottle is placed in freezer, the water would freeze and would expand resulting in the bottle to break.
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