1. Temperature, Heat, & Expansion
Chapter 15

2. Temperature

3. Temperature
We a express temperature of some quantity of matter by number that correspond to its degree of hotness or coldness on some chosen scale.

4. Galileo invented the first “thermal meter” for measuring temperature.
The thermometer
Thermal is the Greek term for heat
Galileo’s Thermometer – How It Works

5. What are the three scales that we use to measure temperature?
What is zero on each of these scales?

6. Heat

7. Heat is defined as the energy transferred from one object to another because of a temperature difference between them.
The direction of spontaneous energy transfer is always from a warmer object to a neighboring cooler object.

8. Does Matter Contain Heat?
Matter does not contain heat.
Matter contains:
Molecular kinetic energy
Possibly potential energy

9. Heat is energy in transit from a body of higher temperature to one of lower temperature.
Once transferred, the energy ceases to be heat.

10. Internal Energy The grand total of all energies inside a substance.
In addition to the translational kinetic energy of moving molecules in a substance, there is energy in other forms.
Rotational kinetic energy of molecules
Kinetic energy due to internal movements of atoms within molecules
Potential energy due to the forces between molecules.

11. When a substance absorbs or gives off heat, the internal energy of the substance increases or decreases.
For two things in thermal contact, heat flow is from the higher-temperature substance to the lower-temperature substance.

12. What happens in the following situation – in terms of heat flow?
Red-hot thumbtack
Bowl of hot water

13. Measuring Heat
Since heat is a form of energy, it’s measured in joules.
In the US we more commonly measure unit in calories.
The calorie is defined as the amount of heat required to change temperature of 1 gram of water 1 ⁰C

14. Specific Heat Capacity

15. Different substances have different capacities for storing internal energy.
Different materials require different quantities of heat to raise the temperature of a given by a specified number of degrees.
Different materials absorb energy in different ways.

16. Generally a combination of both occurs.
Energy may increase
The internal motion of molecules
Which raises the temperature
The amount of internal vibration or rotation within molecules and go into potential energy
Which does not raise the temperature
Generally a combination of both occurs.

17. Specific Heat Capacity
The specific heat capacity of any substance is defined as the quantity of heat required to change the temperature of a unit of mass of the substance by 1 degree.

18. Specific Heat Capacity Cont.
𝑄=𝑐𝑚∆𝑇
Q – Heat transferred
c – Specific heat capacity
m – Mass
ΔT – Temperature change

19. We can think of specific heat capacity as thermal inertia.
Inertia is an objects resistance to a change in its state of motion
Specific heat capacity is a sort of thermal inertia since it signifies the resistance of a substance to a change in its temperature

20. Thermal Expansion

21. The result is an expansion of the substance.
When the temperature of a substance is increased, its molecules or atoms move faster and further apart on average
The result is an expansion of the substance.
All 4 of the states of matter will expand as temperature increases.
There are a few notable expectations to this statement

22. The expansion of substances must be accommodated in structures and devices of all kinds.

23. Examples…