Class 7 Science Curiosity Chapter 7 MCQ – Heat Transfer in Nature

Conduction transfers heat from a hotter part of a material to a colder part. The chapter demonstrates this with a metal strip heated at one end, where heat travels along the strip and melts the wax holding the pins.

The pin nearest the flame falls first because the wax holding it becomes hot and melts first. Heat then travels farther along the metal strip, causing the other pins to fall in order as their wax also melts.

In conduction, neighbouring particles pass heat along the material without moving bodily from one part of the object to another. This differs from convection, in which the movement of the liquid or gas itself carries heat between places.

Steel is a metal and is listed as a good conductor of heat. It allows heat to pass through relatively easily. Wood, air, and porcelain are examples of poor conductors and are useful where heat transfer should be reduced.

Woollen fabric traps air in its pores, and air is a poor conductor of heat. This trapped air reduces heat flow from our warm bodies to colder surroundings, helping us feel warm without the fabric needing to produce heat itself.

Air trapped between two blankets is a poor conductor of heat. It reduces the loss of heat from the body to the surroundings. The chapter uses this example to explain why layers can provide useful insulation during cold weather.

Air near the candle warms and expands, making it lighter than the surrounding cooler air. It rises into the inverted cup and causes that side of the arrangement to rise. The activity introduces the movement of heated air.

Convection transfers heat through the actual movement of a liquid or gas. Warm fluid rises and cooler fluid takes its place in the chapter’s examples. This movement helps distribute heat through the air or water being warmed.

The experiment shows that soil heats up faster than water and also cools down faster. This difference helps explain why the direction of coastal breezes changes between day and night as land and sea temperatures change.

A sea breeze moves from the sea towards the land, usually during the day. The land heats faster, warming the air above it. As that warm air rises, cooler air from over the sea moves in to replace it.

At night, land cools faster than sea water. Warmer air over the sea rises, and cooler air from the land moves towards the sea. This movement is called a land breeze and reverses the usual daytime direction.

Radiation can transfer heat without a material medium. This explains how heat from the Sun reaches the Earth. Conduction and convection require matter because their heat transfer depends on particles passing heat or moving from place to place.

The water cycle describes water moving repeatedly between the Earth’s surface and the atmosphere. It includes evaporation, movement through plants and the ground, and return through precipitation. This process helps redistribute and replenish water in different places.

Precipitation is water returning from clouds as rain, snow, or hail. It is part of the water cycle. After reaching the surface, this water may enter rivers and other water bodies or seep into the ground below.

Infiltration is the entry of surface water into soil and rocks. Water moves more readily where spaces are open and connected. The chapter explains that this process helps water reach underground storage areas and contributes to groundwater supplies.

Water seeps fastest through gravel because the spaces between its particles are larger. It moves more slowly through sand and slowest through clay in the activity. The comparison links the size of spaces with the ease of water movement.

Aquifers are underground layers of sediments and rocks that hold water in their spaces. Wells and bore wells can draw from this stored groundwater. The chapter explains that these supplies depend on recharge and are not unlimited.

Warm smoke rises because it is warmer and lighter than the surrounding air. A detector on the ceiling is therefore suitably placed to detect rising smoke. This question applies the chapter’s explanation of the upward movement of heated air.

Ice stupas store water in tall frozen structures during winter. The ice melts slowly later and provides water for farming and other needs. The chapter presents this as an innovative response to water shortages during the warmer part of the year.

he chapter explains that light-coloured surfaces reflect much of the heat that falls on them. Darker surfaces absorb more. Therefore, light-coloured clothes can help reduce the heat absorbed from sunlight and feel more comfortable during hot weather.

Heat moves from the hot end to the cooler end through the metal by conduction. The spoon does not need to circulate through the water. This matches the chapter’s description of heat passing along a solid through neighbouring particles.

Water near the heat source warms, expands, and becomes lighter. It rises while cooler, heavier water moves down to take its place. This continuing movement forms the convection process that distributes heat through the water in the beaker.

Radiation can carry heat through empty space because it does not need a material medium. Conduction requires particles to pass heat along, while convection requires moving matter. The absence of matter between these objects therefore rules out those two paths.

Woollen cloth traps air, which is a poor conductor of heat. Around an ice piece, this insulation slows heat entering from warmer surroundings. Insulation can therefore help keep a cold object cold as well as keep a warm object warm.

Air is a poor conductor, while metals such as copper, steel, and aluminium conduct heat well. A trapped air layer therefore reduces heat flow between the walls. Metal connections would provide easier paths for heat to pass through the box.

Air warmed by the heater expands and becomes lighter than the surrounding cooler air. It rises, while cooler air moves in to replace it. This circulation carries heat through the room and is an example of convection in a gas.

Land warms faster than water during the day but also cools faster at night. The warmer surface therefore changes between land and sea. Air rises above the warmer surface, while cooler air moves towards it, reversing the breeze’s direction.

Concrete surfaces reduce the open ground through which rainwater can seep. The chapter connects increasing concrete cover with reduced infiltration and groundwater depletion. Rainwater harvesting and recharge pits can help return more water to underground storage areas.

The sequence shows water moving through several parts of the water cycle. Rain returns water to land, rivers carry it towards larger water bodies, and evaporation returns some to the air. The chapter describes this as continuing redistribution.

Conduction needs particles to pass heat to neighbouring particles, and convection needs a moving liquid or gas. Both therefore require a material medium. Radiation differs because it can carry heat even where no such medium is present.