1. Forces, Motion, and Energy Ch. 6, Sec. 1 8th Grade - Mrs. Boguslaw
Temperature
Forces, Motion, and Energy Ch. 6, Sec. 1
8th Grade - Mrs. Boguslaw

2. What is temperature?
a measure of the average kinetic energy of the particles in an object
the faster an atom or molecule is moving, the more kinetic energy it has
a measure of how hot (or cold) something is

3. What is temperature?
temperature DOES NOT depend on how much of a substance you have

4. Particle Movement Particles of matter are ALWAYS moving
…but in different directions
…and at different speeds
We can’t measure the kinetic energy of every particle, so we measure the average kinetic energy

5. Measuring Temperature
Tool : thermometer
How does it work? Thermal expansion
thermal expansion: an increase in the size of a substance in response to an increase in the temperature of the substance
as temperature increases, particles move faster and faster and spread out…which takes up more room!

6. Thermal Expansion at Work
Expansion joints on highways
Hot air balloons

7. Temperature scales

8. Temperature Scales Measured in… degrees Celsius degrees Fahrenheit
Kelvins

9. Absolute Zero Absolute zero = 0 Kelvins
The temperature at which atom movement STOPS
Has not been achieved, but scientists have gotten close

10. Temperature Conversions

11. Forces, Motion, and Energy Ch. 6, Sec. 2 8th Grade - Mrs. Boguslaw
What is Heat?
Forces, Motion, and Energy Ch. 6, Sec. 2
8th Grade - Mrs. Boguslaw

12. Heat
Heat: the energy transferred between objects that are at different temperatures
Heat moves; cold doesn’t!

13. Thermal Energy
thermal energy: the kinetic energy of a substance’s atoms

14. Conduction
thermal conduction - the transfer of thermal energy from one substance to another through DIRECT CONTACT
Example: when you put a hot spoon in a hot liquid, the end of the spoon eventually gets hot

16. Conductors and Insulators
thermal conductor - a material through which energy can be transferred as heat
thermal insulator - a material that reduces or prevents transfer of heat

17. fiberglass insulation
Conductors
Insulators
curling iron
flannel shirt
cookie sheet
oven mitt
iron skillet
plastic spatula
copper pipe
fiberglass insulation
stove coil
ceramic bowl

18. Convection
convection - the transfer of thermal energy by the circulation or movement of a liquid or gas
Example: boiling water repeatedly rises and sinks, wind is created by convection currents

20. Radiation radiation - the transfer of energy as electromagnetic waves
Example: portable heater, the sun

21. Thermal Conductivity
thermal conductivity - the rate at which a substance conducts thermal energy
high thermal conductivity —> heat transfers easily
low thermal conductivity —> heat doesn’t move through it easily

22. Specific Heat
specific heat - the quantity of heat required to raise a unit mass of a homogenous material 1K or 1ºC
conductors - low specific heats
insulators - high specific heats
Do you expect the specific heat of water to be low or high?

23. Calculating Heat heat = specific heat x mass x change in temperature
heat = Joules (J)
specific heat = J/kg x ºC
mass = kg
temperature = ºC

24. Forces, Motion, and Energy Ch. 6, Sec.3 8th Grade - Mrs. Boguslaw
Matter and Heat
Forces, Motion, and Energy Ch. 6, Sec.3
8th Grade - Mrs. Boguslaw

25. States of Matter
states of matter - the physical forms in which a substance can exist
three main states: solid, liquid, and gas

26. Solids
particles do not move fast enough to overcome the strong attraction between them, so they are held tightly in place.
particles vibrate in place

27. Liquids
move fast enough to overcome some of the attraction between them
particles slide past each other

28. Gases
particles move fast enough to overcome almost all of the attraction between them
particles move independently of each other

29. Changes in State
changes in state - the change of a substance from one physical state to another
only a physical change, not a chemical change. It looks different, but identity is the same

31. Forces, Motion, and Energy Ch. 6, Sec.4 8th Grade - Mrs. Boguslaw
Heat Technology
Forces, Motion, and Energy Ch. 6, Sec.4
8th Grade - Mrs. Boguslaw

32. Hot-Water Heating a hot-water heater raises the temperature of water
water is pumped through pipes that go to a radiator in each room
radiators heat the colder air around them
water goes back to the water heater to be reheated

33. Warm-Air Heating
air is heated in a furnace by burning fuel, usually natural gas
Warm air travels to ducts in different rooms
Warm air heats the rooms, cool air sinks down to a vent near the floor
A fan forces cooler air back into the furnace to be heated

34. Heating and Insulation
During cold weather, heat easily escapes a house; during warm weather, heat easily moves into a house
Insulation reduces the transfer of thermal energy
When insulation is used in walls, ceilings, and floors, less heat passes in and out of the building
Keeps homes cooler in the summer (keeps hot air from moving in) and warmer in the winter (keeps hot air from moving out)

35. Solar Heating The sun gives off a LOT of energy
Solar heating systems use the energy of the sun to heat homes and buildings
can be passive (sun heats directly through the building) or active (see picture)
Not great in really cold climates

36. Heat Engines heat engine: a machine that uses heat to do work
heat engines burn fuel through a process called combustion
external combustion engine: fuel burned outside the engine
internal combustion engine: fuel burned inside the engine

37. External Combustion Engine

38. External Combustion Engines
fuel is burned to heat water into steam
Steam expands, which pushes a piston or a turbine
The piston or turbine is attached to other parts of the machine that do work

39. Internal Combustion Engine

40. Internal Combustion Engines
fuel (gasoline) is burned inside the cylinders in the engine
Intake stroke - a mixture of gasoline and air enter the cylinders as the piston moves down
Compression stroke - the crankshaft turns and pushes the piston up, compressing the fuel mixture
Power stroke - a spark plug uses electrical energy to ignite the compressed fuel mixure
As the fuel and air burns, it expands and forces the piston down
Exhaust stroke - crankshaft turns and piston is forced back up, pushing exhaust gases out of the cylinder

41. Cooling Systems
Cooling systems transfer thermal energy out of an area so that it feels cooler
Thermal energy usually travels from higher temperature to lower temperature, so to move thermal energy the opposite way requires work
Most cooling systems (like refrigerators or air conditioners) require electricity to do work

42. Thermal Pollution
thermal pollution: the temperature increase of a body of water that is caused by human activity and has a harmful effect on water quality and the ability of that body of water to support life
Often happens near large power plants
If the temperature of water is increased, it can harm animals that live there and disrupt the ecosystem