# thermal energy

## what is thermal energy

Why do the air and sand of Death Valley feel so hot? Its because their particles are moving very rapidly. Anything that is moving has kinetic energy, and the faster it is moving, the more kinetic energy it has. The total kinetic energy of moving particles of matter is called thermal energy. Its not just hot things such as the air and sand of Death Valley that have thermal energy. All matter has thermal energy, even matter that feels cold. Thats because the particles of all matter are in constant motion and have kinetic energy.

## thermal energy temperature and mass

Thermal energy and temperature are closely related. Both reflect the kinetic energy of moving particles of matter. However, temperature is the average kinetic energy of particles of matter, whereas thermal energy is the total kinetic energy of particles of matter. Does this mean that matter with a lower temperature has less thermal energy than matter with a higher temperature? Not necessarily. Another factor also affects thermal energy. The other factor is mass. Q: Look at the pot of soup and the tub of water in the Figure 1.1. Which do you think has greater thermal energy? A: The soup is boiling hot and has a temperature of 100 C, whereas the water in the tub is just comfortably warm, with a temperature of about 38 C. Although the water in the tub has a much lower temperature, it has greater thermal energy. The particles of soup have greater average kinetic energy than the particles of water in the tub, explaining why the soup has a higher temperature. However, the mass of the water in the tub is much greater than the mass of the soup in the pot. This means that there are many more particles of water than soup. All those moving particles give the water in the tub greater total kinetic energy, even though their average kinetic energy is less. Therefore, the water in the tub has greater thermal energy than the soup. Q: Could a block of ice have more thermal energy than a pot of boiling water? A: Yes, the block of ice could have more thermal energy if its mass was much greater than the mass of the boiling water.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

only matter that feels warm has thermal energy.

``````a. true

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

the thermal energy of matter depends on its

``````a) mass.

b) temperature.

c) number of particles.

-->  d) all of the above
``````

an object with a lower temperature always has less thermal energy than an object with a warmer temperature.

``````a. true

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

which choice has the least thermal energy?

``````-->  a) cup of hot cocoa

b) bathtub full of warm water

c) swimming pool full of cool water

d) all the water in earths oceans
``````

the faster the particles of matter are moving, the greater their kinetic energy is.

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

b. false
``````

the slower the particles of matter are moving, the lower their temperature is.

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

b. false
``````

## diagram questions

No diagram questions associated with this lesson