# heat

## what is heat

Heat is the transfer of thermal energy between substances. Thermal energy is the kinetic energy of moving particles of matter, measured by their temperature. Thermal energy always moves from matter with greater thermal energy to matter with less thermal energy, so it moves from warmer to cooler substances. You can see this in the Figure particles of the cooler substance. Thermal energy is transferred in this way until both substances have the same thermal energy and temperature. Q: How is thermal energy transferred in an oven? A: Thermal energy of the hot oven is transferred to the cooler food, raising its temperature.

## cooling down by heating up

How do you cool down a glass of room-temperature cola? You probably add ice cubes to it, as in the Figure 1.2. You might think that the ice cools down the cola, but in fact, it works the other way around. The warm cola heats up the ice. Thermal energy from the warm cola is transferred to the much colder ice, causing it to melt. The cola loses thermal energy in the process, so its temperature falls.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

heat is a form of energy.

``````a. true

-->  b. false
``````

temperature measures the average kinetic energy of particles.

``````-->  a. true

b. false
``````

thermal energy always moves from cooler to warmer substances.

``````a. true

-->  b. false
``````

thermal energy is transferred between two substances until

``````a) one substance is warmer than the other.

b) both substances are warmer than they were.

c) both substances are cooler than they were.

-->  d) both substances have the same temperature.
``````

thermal energy is transferred between substances only when they have different

``````a) masses.

b) volumes.

-->  c) temperatures.

d) two of the above
``````

## diagram questions

No diagram questions associated with this lesson