1. Ch 15 and 16
Energy and Heat

2. Energy is the ability of an object to cause change
Basic unit is the Joule (J) =Nm

3. 3. Chemical = wood, gasoline 4. Electrical = lightning, batteries
Forms of energy
1. Mechanical = PE+KE
2. Thermal = heat
3. Chemical = wood, gasoline
4. Electrical = lightning, batteries
5. Electromagnetic = visible light, x-rays
6. Nuclear = fission, fusion

4. Kinetic Energy – energy in the form of motion
a. Greater mass, more KE
b. Greater velocity, more KE

5. A 20-kg kid slides down a slide at a velocity of 2 m/s
A 20-kg kid slides down a slide at a velocity of 2 m/s. What is the kinetic energy of the kid?

6. Potential Energy – stored energy
a. Amount depends on:
1. Position
2. Shape

7. a. Higher up, more PE b. Greater mass, more PE
Types of PE:
1. Gravitational – related to height above Earth’s surface
a. Higher up, more PE
b. Greater mass, more PE

8. 2. Elastic – object that is stretched or compressed

9. 3. Chemical – found in food or fuels

10. PE=mgh=Fgh
SI unit is Joule=J=Nm PE mg h

11. A potted plant on a 2. 5 m high window sill has a mass of 3-kg
A potted plant on a 2.5 m high window sill has a mass of 3-kg. What is the potential energy of the plant?

12. A man weighing 950N stands at the top of 30m cliff
A man weighing 950N stands at the top of 30m cliff. What is the man’s potential energy?

13. 3 people of equal mass climb the mt using different paths
3 people of equal mass climb the mt using different paths. Which path shows the person gaining the most PE?

14. Roller coaster
max height PE
speed ME

15. Energy Conversion – process of changing energy from one form to another

17. Law of Conservation of Energy states that matter cannot be created nor destroyed

19. STAR Questions List the 6 forms of energy
Mechanical, chemical, electromagnetic, thermal, electrical, nuclear
Work depends on what 2 things?
Distance and force
KE, chemical PE, elastic PE or gravitational PE?
Bouncing ball
Rock at edge of cliff
Glass of Orange Juice
Car battery
Compressed spring KE
Gravitational PE
Chemical PE
Elastic PE

20. Ch 16-HEAT
Heat =energy that flows from higher temps to lower temps
What will happen to the temperature in the beakers over time?
30oC
90oC

21. Temperature –measure of average KE of the particle in a sample of matter
a. Increase temp = greater KE
b. Decrease temp = lower KE
c. Absolute Zero=0K= KE of all particles cease

22. Thermal Energy – the total energy of the particles in a material (both KE and PE)
a. More mass at the same temp means greater thermal energy

23. KE of 3?
TE of 3?
50oC
70oC
70oC
200g
400g
200g

24. Thermal Expansion & Contraction
a. Hot temps cause materials to expand
b. Cold temps cause materials to contract

25. Specific Heat (C) – amount of energy needed to raise the temp of 1g of a material by 1oC
Think of it as “resistance to temperature change”
The higher the c, the harder it is the change the temp.

26. An iron spoon and a silver spoon have the same mass
An iron spoon and a silver spoon have the same mass. Which becomes hotter when both are left in hot chocolate for one minute? Pg 476 for c values

27. Why does a piece of steel heat up more than an equal mass of wood when both absorb the same energy?
The metal has a lower specific heat than the wood, so its temp increases more as thermal energy is absorbed

28. Which substance will have the greatest increase in temp when equal masses absorb equal amounts of thermal energy?
Water (4.18 J/goC)
Ethyl alcohol (2.43 J/goC )
Ammonia gas (2.1 J/goC )
Aluminum (0.90 J/goC )
Lead (0.46 J/goC )

29. Answer : A

30. The same energy was added to each sample
The same energy was added to each sample. Which material has the highest specific heat?
Al, b/c Temp rises the least for a given amt energy added. Smaller ΔT means a larger specific heat 30

31. Conduction – transfer of energy through matter by direct contact of particles
a. Energy is transferred when particles moving at different speeds collide
b. Occurs in solids, liquids, and gases
1. Solids conduct better

32. Convection – transfer of energy by the movement of matter
a. Fluid – anything that flows
b. Occurs in liquids & gases

33. Radiation –transfer of energy in form of waves
a. Shiny materials reflect radiant energy
b. Dull materials absorb
c. Darker colors absorb more
d. Lighter colors absorb less

34. STAR Questions Decrease temperatures = ___________ KE Decreased
Hot temperatures cause materials to ______
Expand
The higher the C-specific heat, the _________ it is to change the temp
Harder
Dull materials ___________ radiant energy
Absorb
Lighter colors reflect ___________ radiant energy
less