Selina solutions concise physics class 9 icse Solutions for Chapter 6 chapter 6 heat and energy

What is heat? Write its S.I unit.

Two bodies at different temperatures are placed in contact. State the direction in which heat will flow

Name the S.I. unit of heat. How is it related to the unit calorie?

Define temperature and write its S.I unit.

Describe an experiment to show that water has maximum density at 4℃. What important consequences follow from this peculiar property of water? Discuss the importance of this phenomenon in nature.

Why does a piece of ice when touched with hand, appear cool? Explain

Distinguish between heat and temperature

What do you understand by the thermal expansion of a substance?

Name two substances which expand on heating

Name two substances which contract on heating

What do you mean by the anomalous expansion of water?

At what temperature the density of water is maximum? State its value

State the volume changes observed when a given mass of water is heated from 0℃ to 10℃.

Sketch a temperature-volume graph to show the behavior

Draw a graph to show the variation in the density of water with temperature in the temperature range from 0℃ to 10℃.

A given mass of water is cooled from 10℃ to 0℃. State the volume changes observed.

Represent these changes on a temperature-volume graph.

A deep pond of water has its top layer frozen during the water. State the expected temperature of the water layer (i) just in contact with ice, (ii) at the bottom of the pond.

Draw a labelled diagram showing the temperature of various layers of water in an ice-covered pond.

Explain the following:

(a) Water pipes in colder countries often burst in winter.

(b) In winter, the water tank (or ocean) starts freezing from the surface and not from the bottom

(c) Fishes survive in ponds even when the atmospheric temperature is below 0℃

(d) A hollow glass sphere that floats with its entire volume submerged in water at 4℃ sinks when water is heated above 4℃.

(e) A glass bottle completely filled with water and tightly closed at room temperature, is likely to burst when kept in the freezer of a refrigerator.

1. Calorie is the unit of:

(a) Heat

(b) Work

(c) Temperature

(d) Food

1 J equals to:

(a) 0.24 cal

(b) 4.28 cal

(c) 1 cal

(d) 1 kcal

S.I. unit of temperature is:

(a) cal

(b) joule

(c) celsius

(d) kelvin

Water is cooled from 4℃ to 0℃. It:

(a) Contracts

(b) Expands

(c) First contracts, then expands

(d) First expands, then contracts

The density of water is maximum at:

(a) 0℃

(b) 100℃

(c) 4℃

(d) 15℃

What is an ecosystem? Name its two components

What is the source of energy for all ecosystems

State the importance of green plants in an ecosystem

Differentiate between the producers and consumers

State the functions of decomposers in an ecosystem

What is a food chain

Draw a simple diagram showing a food chain

Describe the energy flow in an ecosystem.

State the law which governs the energy flow in an ecosystem

Show that the energy flow in an ecosystem is linear

Draw a simple diagram showing the energy flow in a food chain

Draw a diagram to show that the energy flow in an ecosystem is governed by the law of

conservation of energy

Food chain begins with:

(a) Respiration

(b) Photosynthesis

(c) Decomposition

(d) Decay

The source of energy in an ecosystem is:

(a) Sun

(b) Decayed bodies

(c) Green plants

(d) Sugar

Energy enters in a food chain through:

(a) Primary consumers

(b) Secondary consumers

(c) Tertiary consumers

(d) Producers

The place of human beings in food chain in an ecosystem is as a:

(a) Producer

(b) Consumer

(c) Decomposer

(d) Both (a) & (b)

State two characteristics which a source of energy must have

Name the two groups in which various sources of energy are classified. State on what basis are they classified

What is meant by renewable and non-renewable sources of energy? State two differences between them, giving two examples of each,

Select the renewable and non-renewable sources of energy from the following:

(a) Coal

(b) Wood

(c) Water

(d) Diesel

(e) Wind

(f) Oil

Why is the use of wood as a fuel is not advisable although wood is a renewable source of

energy?

Name five renewable and three non-renewable sources of energy

What is (i) tidal, (ii) ocean and (iii) geo thermal energy? Explain in brief

What is the main source of energy for the earth

What is solar energy? How is solar energy used to generate electricity in a solar power plant?

What is a solar cell? State two uses of solar cells. State whether a solar cell produces a.c. or d.c. Give one disadvantage of using a solar cell

State two advantages and two limitations of producing electricity from solar energy

What is wind energy? How is wind energy used to produce electricity? How much electric power is generated in India using wind energy?

State two advantages and two limitations of using wind energy for generating electricity

What is hydro energy? Explain the principle of generating electricity from hydro energy.

How much hydro electric power is generated in India

State two advantages and two disadvantages of producing hydro-electricity

What is nuclear energy? Name the process used for producing electricity using the nuclear

energy.

What percentage of total electrical power generated in India is obtained from nuclear power plants? Name two places in India where electricity is generated from nuclear power plants?

State two advantages and two disadvantages of using nuclear energy for producing electricity.

State the energy transformation in the following:

(i) Electricity is obtained from solar energy

(ii) Electricity is obtained from wind energy

(iii) Electricity is obtained from hydroelectricity

(iv) Electricity is obtained from nuclear electricity

State four ways for the judicious use of energy.

What do you mean by the degradation of energy? Explain it by taking two examples of your daily life

The conversion of part of energy into an unuseful form of energy is called ______

The ultimate source of energy is:

(a) Wood

(b) Wind

(c) Water

(d) Sun

Renewable source of energy is:

(a) Coal

(b) Fossil fuels

(c) Natural gas

(d) Sun

What do you mean by greenhouse effect

Name three green house gases

Which of the following solar radiations pass through the atmosphere of the earth?

X-rays, ultraviolet rays, visible light rays, infrared radiation

Name the radiations which are absorbed by the green house gases

What would have been the temperature of the earth’s atmosphere in absence of green house gases in it?

State the effect of green house gases on the temperature of earth’s atmosphere

What do you mean by global warming?

What causes the rise in atmospheric temperature?

State the cause of the increase of greenhouse effect

What will be the effect of global warming at the poles

State the effect of global warming in coastal regions

How will global warming affect the sea level?

How will global warming affect agriculture

State two ways to minimize the impact of global warming

What is carbon tax? Who will pay it?

The green house gas is:

(a) Oxygen

(b) Nitrogen

(c) Chlorine

(d) Carbon dioxide

The increase of carbon dioxide gas in atmosphere will cause:

(a) Decrease in temperature

(b) Increase in temperature

(c) No change in temperature

(d) Increase in humidity

Without the greenhouse effect, the average temperature of the earth’s surface would have been:

(a) -18℃

(b) 33℃

(c) 0℃

(d) 15℃

Global warming has resulted in:

(a) The increase in yield of crops

(b) The decrease in sea levels

(c) The decrease in human deaths

(d) The increase in sea levels