Heat - Class 7 Science Free MCQ Test with solutions

In the summer, we feel more comfortable wearing light-colored clothes because they reflect most of the heat that falls on them. This keeps us cooler compared to dark-colored clothes, which absorb more heat. So, when it's hot outside, light-colored clothes help us stay cool!

Laboratory thermometers are typically designed to measure from -10°C to 110°C. This range allows them to cover temperatures from below the freezing point of water (0°C) to slightly above the boiling point of water (100°C), which is useful for a variety of experiments, including those involving boiling and freezing points.

The heat from the Sun reaches us through the process of radiation. The radiant heat travels similar to the speed of light.

There are millions of miles of empty space between the Earth and the Sun. Therefore, only through radiation can heat be transferred to the Earth from the Sun, as it does not require any medium.

In the day-time, the sun heats both the land and the sea. Land heats up more quickly than the water. Hence, it is hotter than the sea. As you know, hot air is lighter than the cold air. Therefore, warm air above the land rises. The cool air from the sea comes in to take its place. This is known as sea breeze. It cools the land near the coast.

At night, the water cools down more slowly than the land. So, the cool air from the land moves towards the sea.This is called the land breeze. Hence correct option is C.

The materials which allow heat to pass through them easily are conductors of heat. Examples: aluminum, iron, and copper.
The materials which do not allow heat to pass through them easily are poor conductors of heat and are known as insulators. Examples: plastic and wood.

The heat in metals is conducted by the process of conduction in which molecules in contact, transfer heat to adjacent molecules.

A glass tube is filled with mercury and a standard temperature scale is marked on the tube. With changes in temperature, the mercury expands and contracts, and the temperature can be read from the scale.

When we talk about heat, it actually flows from a hotter object to a colder object, not the other way around. Imagine you have a hot cup of tea and a cold ice cube. If you put the ice cube in the tea, the heat from the tea moves to the ice cube, making the ice cube melt. This shows that heat moves from hot things to cold things.

So, the statement is False.

Iron is a conductor of heat due to the following reasons:

• Metals like iron have free electrons that can move easily, transferring energy quickly.
• This property allows heat to pass through iron efficiently.
• In contrast, materials like wood, plastic, and rubber are insulators. They do not have free electrons, making them poor conductors of heat

Therefore, iron is the correct answer.

Two thin blankets joined together keep us warmer than one thick blanket of the same total thickness because they trap a layer of air between them. Air is a poor conductor of heat, so this trapped air prevents the flow of heat from the body to the cold surroundings, keeping us warm.