1. Thermal Energy: Temperature and Heat
Section 6.1

2. Temperature Are hot and cold relative or absolute terms?
All matter is in constant motion
All materials are made up of atoms and molecules
Faster = more KE
Temperature- the average KE of the atoms or molecules
SI units: Kelvin
K = C + 273

3. Thermal Energy
Energy is transferred from faster (warmer) molecules to slower (cooler) molecules
Occurs through collisions between molecules
Atoms and molecules exert attractive forces on each other- generating potential energy
Just like a ball above the earth- you let it go and it is attracted to the earth
Thermal Energy- the sum of the kinetic and potential energy of all the atoms in an object

4. Thermal Energy Thermal energy increases as temperature increases
At constant temperature, thermal energy increases if mass increases.
Remember KE is mass times velocity squared.
Thermal energy that flows from something at a higher temperature to something at a lower temperature is called heat.

5. Thermal Energy Does heat flow from hot to cold or cold to hot?
Which seems hotter- sand, air, or water- if you are at the beach? Why?
Specific heat capacity- the amount of heat needed to raise the temperature of 1 kg of a material by 1 degree C or K
Water- high specific heat capacity- requires a large amount of energy to increase temperature 1 degree

6. Specific Heat Capacity
Water 4,184 J/(kgK)
Wood 1,760 J/(kgK)
Carbon 710 J/(kgK)
Glass 664 J/(kgK)
Iron 450 J/(kgK)
Which would have the highest temperature if all were exposed to the same amount of energy for 1 hour?
Which would have the lowest temperature?

7. Thermal Energy Which of the materials should we use as a coolant? Why?
Thermal energy changes when heat flows into or out of a substance
Calculating change in thermal energy : change in thermal energy = mass x change in temperature times specific heat
Q = m x (Tf – Ti) x C

8. Thermal Energy
When heat flows into an object, temperature rises, and change in temperature is positive
Q is also positive
Called endothermic
When heat flows out of an object, temperature decreases, and change in temperature is negative
Q is also negative
Called exothermic

9. Thermal Energy
A calorimeter is used to measure specific heat