17.2 Movement of Heat

In an experiment, a piece of ice was wrapped in metal wire gauze and then placed in a test tube of water. A Bunsen flame was then applied to the test tube for five minutes so that only the water at the surface was heated.

Which of the following explains the observation that the ice remained frozen in the experiment?

• Ice is a bad absorber of heat.

• Water is a good conductor of heat.

• Water is a bad conductor of heat.

• Wire gauze is a bad conductor of heat.

In an experiment, a piece of ice was wrapped in metal wire gauze and then placed in a test tube of water. A Bunsen flame was then applied to the test tube for five minutes so that only the water at the surface was heated.

What is the purpose of the wire gauze?

• It conducts heat away from the water.

• It sinks the ice to the bottom of the test tube.

• It conducts heat away from the ice.

• It insulates the ice from the hot water.

Convection is a process of heat transfer that depends on _________.

• density difference in a liquid or a gas

• heavy molecules falling and light molecules rising

• molecules vibrating and then keeping still

• radiation of energy between two places

Which of the following diagrams shows the direction of convection currents when water is heated in a beaker?

• A

• B

• C

• D

Which of the following are the properties of a surface that radiates heat best?

• Rough, dull and black

• Rough, dull and white

• Rough, dull and white

• Rough, dull and white

Which of the following explains how the polar bear is adapted to live in a cold environment?

• Air trapped in the fur reduces heat loss by radiation.

• Air trapped in the fur is a bad conductor of heat.

• The thick layer of fat under the bear’s skin is a good radiator of heat.

• All of the above.

The diagrams below show four bowls of the same size and mass. The bowls are made using different materials. If the same amount of soup at the same temperature was poured into each of them, which bowl would keep the soup hot the longest?

• A

• B

• C

• D

A black tin can is placed in sunlight for a few hours. Its temperature is regularly monitored. The temperature of the can becomes higher than its surroundings. When this happens .

• the can conducts heat away to the surface it is resting on

• the can heats up the air around it

• the can radiates a lot of heat away because the can has become very hot

• all of the above is taking place

Two identical glass beakers are half-filled with equal volumes of water at room temperature. One of the beakers is wrapped in shiny aluminium foil and the other is wrapped in black art paper. Both beakers are left in sunlight. After an hour, the water in _______________________.

• both beakers arrive at the same higher temperature

• both beakers radiate heat and are cooler than before

• the black container is warmer than the shiny container

• the shiny container is warmer than the black container

Heat is transferred from a region of ___________ to a region of ________________

• lower heat, higher heat

• lower temperature, higher temperature

• higher heat, lower heat

• higher temperature, lower temperature