Class 9 Heat and Energy Mock Test (ICSE)

Topics in Heat and Energy

• Heat and temperature
• Anomalous expansion of water and Hope's experiment
• Energy flow in ecosystems
• Renewable and non-renewable sources of energy
• Greenhouse effect and global warming

Heat and Energy practice questions with answers

1. Q1Multiple choice·1 mark
   Which of the following atmospheric gases is chiefly responsible for the enhancement of the greenhouse effect by human activities, leading to global warming?

   1. (a)Argon
   2. (b)Oxygen
   3. (c)Nitrogen
   4. (d)Carbon dioxide
   Show answer and step marks

   1. Correct option: (d) Carbon dioxide. Burning fossil fuels and deforestation have raised its concentration, enhancing the greenhouse effect; nitrogen, oxygen and argon are not greenhouse gases.+1

   Answer: (d)
2. Q2Multiple choice·1 mark
   Which of the following phenomena is primarily demonstrated using Hope's apparatus?

   1. (a)Water boils at $100~^{\circ}\text{C}$ under standard pressure
   2. (b)Water has its maximum density at $4~^{\circ}\text{C}$
   3. (c)Water has maximum volume at $0~^{\circ}\text{C}$
   4. (d)Water expands on freezing into ice
   Show answer and step marks

   1. Correct option: (b) Water has its maximum density at $4~^{\circ}\text{C}$+1

   Answer: (b)
3. Q3Multiple choice·1 mark
   In Hope's apparatus demonstration for the anomalous expansion of water, when the central cylinder is surrounded by a freezing mixture:

   1. (a)lower thermometer ($T_1$) reaches $4^\circ\text{C}$ before upper thermometer ($T_2$) reaches $0^\circ\text{C}$.
   2. (b)upper thermometer ($T_2$) reaches $0^\circ\text{C}$ before lower thermometer ($T_1$) reaches $4^\circ\text{C}$.
   3. (c)both thermometers record $4^\circ\text{C}$ and $0^\circ\text{C}$ at the exact same time.
   4. (d)lower thermometer ($T_1$) reaches $0^\circ\text{C}$ before any change is observed in $T_2$.
   Show answer and step marks

   1. Correct option: (a) lower thermometer ($T_1$) reaches $4^\circ\text{C}$ before upper thermometer ($T_2$) reaches $0^\circ\text{C}$.+1

   Answer: (a)
4. Q4Short answer·2 marks
   State the 10% law of energy flow in an ecosystem. If green plants trap $10,000\text{ J}$ of solar energy, calculate the amount of energy available to the secondary consumer.
   Show answer and step marks

   1. State the 10% law: Only 10% of the energy entering a trophic level is available for transfer to the next trophic level.+1
   2. Energy at producer level = $10,000\text{ J}$. Primary consumer = $10\% \text{ of } 10,000\text{ J} = 1000\text{ J}$. Secondary consumer = $10\% \text{ of } 1000\text{ J} = 100\text{ J}$.+1

   Answer: 10% law: only about 10% of the energy at one trophic level is passed on to the next level (the rest is lost, mostly as heat). Energy available to the secondary consumer $= 100\text{ J}$.
5. Q5Long answer·4 marks
   Answer the following questions based on energy sources: (a) Define renewable sources of energy and give one example of a non-renewable source of energy. (b) State two major environmental advantages of harnessing solar energy compared to using fossil fuels.
   Show answer and step marks

   1. (a) Renewable sources of energy are those sources that are inexhaustible and can be replenished naturally within a relatively short period.+1
   2. (a) Non-renewable example, any one of: coal; petroleum; natural gas; nuclear fuel such as uranium; or any other valid non-renewable source.+1
   3. (b) First advantage, any one of: it releases no carbon dioxide or other greenhouse gases, so it does not add to global warming; it gives out no smoke, soot or oxides of sulphur and nitrogen, so it causes no air pollution or acid rain; it produces no ash while generating electricity; no fuel has to be mined or drilled, so it avoids fuel-mining damage to land and oil spills; or any other valid environmental advantage.+1
   4. (b) Second advantage, a different one from the same list.+1

   Answer: (a) Renewable sources are inexhaustible sources that nature replenishes within a short time; a non-renewable example is coal (or petroleum, natural gas, uranium). (b) Any two of: no carbon dioxide or greenhouse gases, so no addition to global warming; no smoke or sulphur and nitrogen oxides, so no air pollution or acid rain; no ash while generating; no fuel mining or drilling damage or oil spills.
6. Q6Long answer·4 marks
   (a) What are renewable sources of energy? Give two examples. (b) State two environmental advantages of harnessing solar energy instead of burning fossil fuels for electricity generation.
   Show answer and step marks

   1. Definition: Sources of energy that are inexhaustible and get replenished naturally in a short duration.+1
   2. First example, any one of: solar energy; wind energy; hydro energy (flowing water); tidal energy; geothermal energy; biomass or biogas; or any other valid renewable source.+0.5
   3. Second example, a different one from the same list.+0.5
   4. First advantage, any one of: it releases no carbon dioxide or other greenhouse gases, so it does not add to global warming; it gives out no smoke, soot or oxides of sulphur and nitrogen, so it causes no air pollution or acid rain; it produces no ash while generating electricity; no fuel has to be mined or drilled, so it avoids fuel-mining damage to land and oil spills; or any other valid environmental advantage.+1
   5. Second advantage, a different one from the same list.+1

   Answer: (a) Sources that are inexhaustible and replenished naturally in a short time; any two of solar, wind, hydro, tidal, geothermal energy or biomass. (b) Any two of: no carbon dioxide or greenhouse gases, so no addition to global warming; no smoke or sulphur and nitrogen oxides, so no air pollution or acid rain; no ash while generating; no fuel mining or drilling damage or oil spills.

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