1. Chapter 6
Thermal energy

2. 6.1 Thermal Energy, Heat and Temperature
Recall:
Kinetic Energy?
Potential Energy?
Thermal Energy?

3. 6.1 Thermal Energy, Heat and Temperature
Particles in substances are always moving, therefore they always have some amount of kinetic energy.
Faster particles have more kinetic energy.
Slower particles have less kinetic energy.

4. 6.1 Thermal Energy, Heat and Temperature
Particles also have potential energy, due to the attraction of the particles to one another.
The greater the distance between the particles, the greater the potential energy.
Which state has greatest average potential energy; solid, liquid, or gas? Why?
Gas which has greater distance between particles than both liquids and solids.

5. 6.1 Thermal Energy, Heat and Temperature
Thermal Energy- sum of the kinetic and potential energy of the particles that make up a material.
Describes the energy of solids, liquids and gases

6. 6.1 Thermal Energy, Heat and Temperature
Temperature is the average kinetic energy of the particles that make up a material.
Particles that are moving faster have more kinetic energy and higher temperature.
Inside a house vs. outside a house.

7. 6.1 Thermal Energy, Heat and Temperature
Temperature and thermal energy are related but not the same!
As ice melts, there is both water and ice at the same temperature however they do not have the same thermal energy.
Which has more thermal energy? Why?
The average distance between the particles in a liquid is greater than a solid therefore it has more potential and thermal energy.

8. 6.1 Thermal Energy, Heat and Temperature
Average kinetic energy of particles can not be directly measured so how do we determine temperature?
Thermometers
Temperature is measured using three different units:
1. Celsius
2. Fahrenheit
3. Kelvin

9. 6.1 Thermal Energy, Heat and Temperature
Converting from Fahrenheit to Celsius:
°𝐶= (°𝐹−32) 1.8
Converting from Celsius to Fahrenheit:
°𝐹=(°𝐶 x 1.8) + 32

10. 6.1 Thermal Energy, Heat and Temperature
Average room temperature is 37°C. What is this in Fahrenheit?
The average body temperature of a house cat is 101.5 °F. What is this temperature in Celsius?

11. 6.1 Thermal Energy, Heat and Temperature
Converting to Celsius from Kelvin:
°𝐶=𝐾−273
Converting to Kelvin from Celsius:
𝐾=°𝐶+273

12. 6.1 Thermal Energy, Heat and Temperature
The temperature of a boiling pot of water is 373K, what is the temperature in Celsius?
On a cold winter day a thermometer reads -15°C, what is that temperature in Kelvin?

13. 6.1 Thermal Energy, Heat and Temperature
A cold glasses of lemonade has a temperature of -32°F, find that temperature in Kelvin.
The average temperature on Earth is about 57°F, what would be the temperature in Kelvin?

14. 6.1 Thermal Energy, Heat and Temperature
Heat- the movement of thermal energy from a warmer object to a cooler object.
The greater the temperature difference, the more heat transferred.
Heating continues until all objects are the same temperature.

15. 6.2 Thermal Energy Transfers
Thermal energy is transferred in three ways:
Radiation
Conduction
Convection

16. 6.2 Thermal Energy Transfers
Radiation- transfer of thermal energy by electromagnetic waves.
All objects transfer some thermal energy by radiation.
Which transfers more thermal energy hot objects or cold objects?

17. 6.2 Thermal Energy Transfers
Conduction- the transfer of thermal energy by the collisions of particles in direct contact
Particles with higher kinetic energy transfer some to particles with lower kinetic energy.
When kinetic energy is transferred, thermal energy is transferred.

18. 6.2 Thermal Energy Transfers
Thermal Conductors vs. Thermal Insulators
Conductors allow thermal energy to flow easily
Examples: copper, aluminum
Insulators resists the flow of thermal energy.
Examples: plastic, wood

19. 6.2 Thermal Energy Transfers
All materials require a certain amount of energy to change it’s temperature.
This is known as a material’s Specific heat.
That is the amount of thermal energy required to increase the temperature of 1kg of a material 1°C.

20. 6.2 Thermal Energy Transfers
Higher specific heat, more thermal energy required to increase the temperature.
Which has a higher specific heat a thermal conductor or insulator? Why?
Thermal insulator because it resists the flow of thermal energy, requiring more to increase its temperature.

21. 6.2 Thermal Energy Transfers
Water has a very high specific heat meaning it requires a lot of thermal energy to increase the temperature.
Is that good or bad?
Prevents your body from overheating
Keeps pools and oceans cool in the summer
Good for cooling machinery

22. 6.2 Thermal Energy Transfers
𝐻𝑒𝑎𝑡=𝑚𝑎𝑠𝑠 𝑥 𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 ℎ𝑒𝑎𝑡 𝑥 𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒
𝑄=𝑚 𝑐 𝑝 𝑇 𝑓 − 𝑇 𝑖 or 𝑄=𝑚 𝑐 𝑝 Δ𝑇
Heat (Q)- Joules
Specific heat (cp)- Joules/g°C
Mass (m)- g
Temperature (T)-°C

23. 6.2 Thermal Energy Transfers
It takes J to heat 25 grams of copper from 25 °C to 75 °C. What is the specific heat of copper?
A 500g cube of lead is heated from 50 °C to 100 °C. How much energy was used to heat the lead if the specific heat of lead is J/g°C.

24. 6.2 Thermal Energy Transfers
A cook places a 150g potato wrapped in aluminum foil (Cp=0.902 J/g°C) in the oven and it is heated up with 700J of energy. What was the change in temperature?
What is the mass of a ball of iron, if it is heated using 250J of energy to go from 10°C to 100°C and has a specific heat of .134 J/g°C.

25. 6.2 Thermal Energy Transfers
What happens when you take a balloon outside on a cold day?
The balloon shrinks in size due to thermal contraction.
Thermal contraction is a decrease in an materials volume when the temperature decreases.

26. 6.2 Thermal Energy Transfers
When the balloon is heated, the opposite effects occur.
Thermal expansion is when the volume of a material increases as the temperature increases.

27. 6.2 Thermal Energy Transfers
Convection-the transfer of thermal energy by the movement of particles from one part of a material to another.
Only occurs in fluids.
Example: boiling water

28. 6.2 Thermal Energy Transfers
Heating Curve- a graph that shows how the temperature of a substance changes as heat is added.
X-axis: Heat
Y-axis: Temperature (°C)
Horizontal lines represent a change in state

29. 6.2 Thermal Energy Transfers

30. 6.2 Thermal Energy Transfers
Calorimeter- a instrument used to measure heat.