TNPSC Physics Heat and Temperature MCQ 4

TNPSC Physics Heat and Temperature MCQ 4 Questions with Detailed Explanations

The concepts of heat and temperature topic is crucial for scoring well in TNPSC Physics. In this section, each question from the quiz is explained in a simple and exam-oriented way to help you clearly understand the key ideas like heat transfer, temperature scales, and thermal properties of matter.

These explanations are designed not just to give the correct answers, but to strengthen your conceptual clarity with real-life examples and quick revision points. This will help you avoid common mistakes and improve accuracy in upcoming TNPSC exams.

👉 Go through each explanation carefully and revise the concepts to boost your score in General Science.

Q1. Which of the following represents the total heat energy in a body?

Heat energy refers to the total internal energy present in a body due to the motion of its molecules. It depends on factors like mass, temperature, and nature of the substance.

Temperature, on the other hand, only indicates the degree of hotness or coldness and does not represent the total energy content. For example, a bucket of warm water contains more heat energy than a cup of boiling water because of its larger quantity.

👉 Real-life Insight:
A large tank of warm water can transfer more heat than a small cup of hot water.

Key Points:

• Heat energy = total energy of molecules
• Depends on mass + temperature
• Temperature ≠ total heat energy
• Larger quantity → more heat energy

Answer: B. Heat energy

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Q2. When hot water is mixed with cold water, the final temperature will be:

When two substances at different temperatures are mixed, heat flows from the hotter substance to the colder one until both reach the same temperature. This state is called thermal equilibrium.

The final temperature will always lie between the temperatures of the two substances, depending on their quantities and initial temperatures.

👉 Real-life Insight:
Mixing hot and cold water while bathing gives a comfortable medium temperature.

Key Points:

• Heat flows hot → cold
• Final state = thermal equilibrium
• Temperature becomes uniform
• Always between initial values

Answer: D. Between both temperatures

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Q3. Which of the following is used as a heat insulator?

When we wear woolen cloths, Wool acts as an excellent heat insulator because it traps air between its fibers. Air is a poor conductor of heat, so it reduces heat transfer between the body and surroundings.

This is why woolen clothes keep us warm during winter by preventing body heat from escaping.

👉 Real-life Insight:
woolen sweaters keep us warm even in cold climates.

Key Points:

• Wool traps air
• Air is poor conductor
• Prevents heat loss
• Used in winter clothing

Answer: A. Wool

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Q4. The boiling point of water decreases when:

The boiling point of a liquid depends on atmospheric pressure. When pressure decreases (like in high-altitude areas), molecules require less energy to escape into vapor, so boiling occurs at a lower temperature.

This is why cooking takes longer in hill stations.

👉 Real-life Insight:
At hill stations, water boils below 100°C, so food cooks slower.

Key Points:

• Boiling point depends on pressure
• Lower pressure → lower boiling point
• High altitude effect
• Cooking becomes slower

Answer: C. Pressure decreases

👉 Exam Tip: TNPSC often asks conceptual questions on heat transfer and daily-life applications.

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Q5. Which of the following is an example of conduction?

Conduction is the transfer of heat through direct contact between particles without any movement of the substance as a whole.

In a metal rod, heat travels from the hot end to the cold end because particles transfer energy through vibrations and collisions. Metals are good conductors due to free electrons.

👉 Real-life Insight:
A metal spoon gets hot when placed in hot tea.

Key Points:

• Heat transfer by direct contact
• No bulk movement
• Common in solids
• Metals are good conductors

Answer: C. Heating one end of a metal rod

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Q6. Why are desert days very hot and nights very cold?

In Deserts, there is very little water vapor in the air. Water vapor acts like a natural heat trap, absorbing and retaining heat. Due to its absence in the deserts, heat from the Sun quickly raises temperature during the day, and at night, heat escapes rapidly into the atmosphere.

👉 Real-life Insight:
Desert regions experience extreme temperature variation between day and night.

Key Points:

• Low water vapor in air
• No heat retention
• Rapid heating (day)
• Rapid cooling (night)

Answer: A. Lack of water vapor

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Q7. Which of the following expands on heating and contracts on cooling?

When substances are heated, their molecules gain kinetic energy and move farther apart, causing expansion. On cooling, molecules lose energy and come closer, resulting in contraction. This behavior is generally seen in solids, liquids, and gases.

👉 Real-life Insight:
Railway tracks are laid with gaps to allow expansion during hot weather.

Key Points:

• Heating → expansion
• Cooling → contraction
• Applies to all states of matter
• Due to molecular motion

Answer: C. All substances

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Q8. Heat transfer in air mainly occurs by:

In gases like air, heat transfer mainly occurs through convection, where heated particles move upward and cooler particles move downward, forming convection currents. This movement transfers heat efficiently in fluids.

👉 Real-life Insight:
Hot air rises, which is why ceilings are warmer than floors.

Key Points:

• Convection in fluids (liquids & gases)
• Hot air rises, cold air sinks
• Forms convection currents
• Major heat transfer in air

Answer: B. Convection

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Q9. Why are cooking vessel handles made of plastic or wood?

Plastic and wood are poor conductors of heat, meaning they do not allow heat to pass through easily. This prevents heat from reaching our hands and protects us from burns while handling hot utensils.

👉 Real-life Insight:
Cookware handles stay cool even when the vessel is hot.

Key Points:

• Poor conductors (insulators)
• Prevent heat transfer
• Safe handling of utensils
• Used in cookware design

Answer: B. They are poor conductors

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Q10. Which of the following has the highest heat energy at the same temperature?

Steam has higher heat energy than water or ice at the same temperature because it contains latent heat of vaporization. This is the extra energy absorbed during the change of state from liquid to gas.

👉 Real-life Insight:
Steam causes more severe burns than boiling water.

Key Points:

• Steam contains latent heat
• Same temperature ≠ same heat energy
• Gas state holds more energy
• Important TNPSC concept

Answer: A. Steam

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Q11. When a liquid is heated, its molecules:

Heating increases the kinetic energy of molecules, making them move faster. As their motion increases, the distance between molecules also increases, leading to expansion.

👉 Real-life Insight:
Water expands when heated in a container.

Key Points:

• Heating increases kinetic energy
• Molecules move faster
• Expansion occurs
• Common in liquids

Answer: B. Move faster

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Q12. Refrigerators remove heat mainly by:

Refrigerators work on the principle of evaporation. The refrigerant inside absorbs heat from the interior while evaporating, thus cooling the space. The absorbed heat is then released outside.

👉 Real-life Insight:
Cooling happens because heat is removed, not added.

Key Points:

• Based on evaporation
• Absorbs heat inside
• Releases heat outside
• Continuous cooling cycle

Answer: D. Evaporation

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Q13. Which of the following is best for keeping liquids hot for a long time?

A thermos flask is designed to minimize heat loss by reducing conduction, convection, and radiation. It uses vacuum insulation to prevent heat transfer, keeping liquids hot or cold for long periods.

👉 Real-life Insight:
Hot tea stays warm for hours in a flask.

Key Points:

• Prevents all 3 heat transfer modes
• Uses vacuum insulation
• Maintains temperature
• Highly efficient

Answer: A. Thermos flask

👉 Exam Tip: TNPSC often asks conceptual questions on heat transfer and daily-life applications.

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Q14. Why do we sweat more on a hot day?

Sweating helps regulate body temperature. When sweat evaporates, it absorbs heat from the body, producing a cooling effect. This process is essential for maintaining body temperature.

👉 Real-life Insight:
You feel cooler after sweating due to evaporation.

Key Points:

• Evaporation causes cooling
• Removes body heat
• Natural temperature control
• Important survival mechanism

Answer: C. To cool the body

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Q15. Which of the following processes releases heat?

Condensation is the process in which gas changes into liquid, releasing heat to the surroundings. This is the opposite of evaporation, which absorbs heat.

👉 Real-life Insight:
Water droplets forming on a cold surface release heat.

Key Points:

• Gas → liquid change
• Releases heat
• Opposite of evaporation
• Common in nature

Answer: D. Condensation

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Q16. The temperature of boiling water remains constant because:

During boiling, the heat supplied is used to change the state of water from liquid to vapor. This energy is called latent heat, and it does not increase temperature.

👉 Exam Tip: TNPSC often asks about latent heat and change of state.

Key Points:

• Heat used for phase change
• Temperature remains constant
• Latent heat concept
• Important exam topic

Answer: A. Heat is used for change of state

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Q17. Which of the following is a good conductor of heat?

Copper is a good conductor of heat because it contains free electrons that transfer heat energy quickly. This makes it suitable for cooking utensils and electrical applications.

👉 Real-life Insight:
Copper vessels heat up quickly and evenly.

Key Points:

• Free electrons transfer heat
• High conductivity
• Used in utensils
• Efficient heat transfer

Answer: D. Copper

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Q18. Why does ice float on water?

Ice floats because it has lower density than liquid water. When water freezes, its structure expands, making it lighter compared to liquid form.

👉 Real-life Insight:
Icebergs float on oceans.

Key Points:

• Ice less dense than water
• Expansion on freezing
• Floats on surface
• Unique property of water

Answer: A. It is less dense

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Q19. Land breeze occurs due to:

At night, land cools faster than the sea. As a result, air above land becomes cooler and moves toward the warmer sea, creating a land breeze.

👉 Real-life Insight:
Fishermen use land breeze to move from land to sea at night.

Key Points:

• Occurs at night
• Land cools faster
• Air moves land → sea
• Convection-based process

Answer: D. Nighttime cooling

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Q20. Which of the following is the best example of convection?

Boiling water is a classic example of convection. When water is heated, the hot water rises and cooler water sinks, creating continuous circulation known as convection currents.

👉 Exam Tip: Conduction = solids, Convection = fluids, Radiation = no medium.

Key Points:

• Heat transfer by fluid movement
• Hot rises, cold sinks
• Forms convection currents
• Seen in boiling liquids

Answer: C. Boiling water

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Final Revision Tips – Heat and Temperature

• Heat flows from hot → cold until thermal equilibrium is reached
• Heat ≠ Temperature (Heat = energy, Temperature = measure of hotness)
• Learn 3 modes of heat transfer: Conduction, Convection, Radiation
• Metals → good conductors, Wood/Plastic → insulators
• Steam has more heat than water at same temperature (latent heat)
• Boiling point decreases when pressure decreases (important for hill stations)
• Evaporation causes cooling (sweating concept)
• Ice floats because it is less dense than water
• Remember units: Heat → Joule, Temperature → Kelvin
• Focus on real-life applications (very important for TNPSC)

🔗 Learn more:

For detailed practice and concept clarity, refer NCERT Exemplar problems on Heat:
👉 https://ncert.nic.in/pdf/publication/exemplarproblem/classVII/Science/geep104.pdf