1. Heat
Heat is a form of Energy Transfer
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2. Temperature
Temperature is defined as a measure of the average kinetic energy of the molecules. This is often called the internal energy of an object.
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3. 06-01 Temperature and Thermal Expansion
The width of 1°C = 9/5°F

4. 06-01 Temperature and Thermal Expansion
Convert 30°C to K
303 K
𝑇_𝐶=5/9(𝑇_𝐹−32)
30=(5/9)(𝑇_𝐹−32)
54=𝑇_𝐹−32
86=𝑇_𝐹
𝑇_𝐾=𝑇_𝐶
𝑇_𝐾=
𝑇_𝐾=303.15

5. 06-01 Temperature and Thermal Expansion
Heat always flows from hotter object to colder object until thermal equilibrium
Zeroth Law of Thermodynamics
If A and B are in equilibrium, and B and C are in equilibrium, then A and C are in equilibrium

6. 06-01 Temperature and Thermal Expansion
Normal Solids
How do you open a glass jar if the metal lid is too tight?
Run it under hot water
The lid expands as the temperature increases

7. 06-01 Temperature and Thermal Expansion
Even small changes in length can have serious consequences
Have you ever seen expansion joints in bridges?
If the space is not provided for expansion, then the road/bridge would buckle

9. 06-01 Temperature and Thermal Expansion
A steel bridge is 2 km long. If the temperature when it was built was 21°C (70°F), what length expansion joints are needed to prevent buckling at 43°C (110°F)?
ΔL = m
Δ𝐿=𝛼𝐿Δ𝑇
Δ𝐿=(12×〖10〗^(−6) °𝐶^(−1) )(2000 𝑚)(43 °𝐶−21 °𝐶)=0.528 𝑚

10. 06-01 Temperature and Thermal Expansion
Bimetallic Strip
Made from two strips of metal that have different coefficients of linear expansion
One side expands more than the other causing the strip to bend
Used in automatic switches in appliances and thermostats
Coffee maker described on p344

11. 06-01 Temperature and Thermal Expansion

12. 06-01 Temperature and Thermal Expansion
Why do fluids in the car usually have a reservoir tank (radiator, brake fluid, power steering fluid, oil)?
As the fluids heat, the volume increases
There needs to be some place for the extra fluid to go

13. 06-01 Temperature and Thermal Expansion
Water
Water is unique
The volume of water decreases from 0°C to 4°C
Then water expands from 4°C and up
Water is the densest (least expanded) at 4°C
As the weather gets cold, the lake water cools and sinks because it becomes more dense pushing the warmer water up
After all the water is 4°C, the top starts to freeze
Because the 0°C water is less dense than the 4°C water, it floats
The ice floats and provides insulation for the warmer water underneath so it does not freeze

14. 06-01 Homework
Expand your mind with these questions
Read 13.3, 13.4

15. 06-04 Heat and Temperature Change
Heat is energy that flows from a higher-temperature object to a lower-temperature object because of the difference in temperatures
Unit: Joule (J), calorie (cal), kilocalorie (kcal or Cal)
If an object feels hot, the heat is flowing into you
If an object feels cold, the heat is flowing out of you
Mechanical Equivalent of Heat
Since heat is energy, other types of energy can make the same effect as heat
1.000 kcal = 4186 J
Results when internal energy from kinetic energy of molecules is transferred
Calorie = raise 1 g of water 1 °C
Kilocalorie = 1000 calories = raise 1 kg of water 1 °C

16. 06-04 Heat and Temperature Change

17. 06-04 Heat and Temperature Change
Measuring the change in temperature of different heated objects (usually water and an unknown) inside a thermos can be used to measure the specific heat capacity of the object
This can be used to identify the unknown material

18. 06-04 Heat and Temperature Change
𝑄 = 𝑚𝑐Δ𝑇
𝑄 = (4186 𝐽/(𝑘𝑔 °𝐶))(10 𝑘𝑔)(100°𝐶−15°𝐶)
𝑄 = 𝐽

19. Chapter 16
Heat Transfer
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20. Conduction Heat transfer through physical contact
In order for conduction to occur the two objects must begin at different temperatures. Objects at the same temperature will not transfer heat and are said to be at thermal equilibrium.
Each material has an innate ability to absorb or give off heat – specific heat
The amount of heat an object can transfer depends upon three things:
The mass of the object, m (in Kg)
The specific heat of the object, Cp ( in J/g°C)
The temperature change of the object, t (in ºC)
Heat is transferred according to the equation:
Q = mCpt
The heat transferred is measured in a unit called a calorie.
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21. Convection
Unlike conduction which transfers energy without transferring mass, convection requires a current – or mass movement of molecules in a fluid.
Keep in mind that a fluid in physics is either a liquid or a gas
Convection occurs because when fluids are heated they become less dense and rise past the colder, denser molecules – this creates the current which allows for heat transfer
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22. Convection Wind is a form of convection
Using the furnace in your house is a form of convection
Boiling water is also a form of convection
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23. Radiation
Radiation is the transfer of energy via an electromagnetic wave.
Electromagnetic waves include radio waves, microwaves, and light
Packets of energy called photons are carried on a wave front
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24. The Greenhouse Effect
A car parked in the sun can get significantly hotter than the outside temperature, this is the greenhouse effect. It occurs because the glass windows let heat in as an electromagnetic wave (sunlight), but then don’t let the resulting heat waves back out.
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25. Solar Power
Solar Power is the rate at which the Earth receives energy from the sun.
Solar power can be used by either passive solar heating (greenhouse effect) or by using photovoltaic cells, also called solar panels, to convert the solar energy to electricity.
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26. Change of Phase
Chapter 17
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27. Phases Changes
Phase changes require that a substance absorb energy or release energy to occur.
There is NO Change in Temperature associated with a phase change!
Different words are used to denote direction when dealing with a phase change.
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28. Vocabulary of a Phase Change
Freezing – change from liquid to solid.
Energy is released!
Melting – change from solid to liquid
Energy is absorbed!
Both of these changes happen at the same point; 0° C for water!
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29. Vocabulary of a Phase Change
Condensing – change from gas or vapor to a liquid.
Energy is released!
Boiling – change from liquid to gas or vapor
Energy is absorbed!
Vapor is the gas phase of any substance which is normally a liquid at room temperature!
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30. Energy Required for a Phase Change
Just like specific heat is a set amount of energy for each substance – the amount of energy required for a phase change is also substance specific.
Heat of Fusion – ΔHf , is the amount of energy absorbed or released when a substance melts or freezes!
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31. Energy Required for a Phase Change
Heat of Vaporization – ΔHv , is the amount of energy absorbed or released when a substance boils or condenses!
Mathematically:
Q = mΔHf for Fusion or
Q = mΔHv for Vaporization
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32. 400,000 calories or 400 Kilocalories
Sample Problem
How much heat is required to melt 5 kg of ice at 0° C?
Solution
Q = mΔHf = (5000 g)(80 calories/g) =
400,000 calories or 400 Kilocalories
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33. Phase Diagram
120
100 -5
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