1. Chapter 6
Heat

2. Heat What words would you use to describe heat?
Flame is a hot gas that will burn you if you touch it.
It is so hot that it glows.
The flame produces heat.
In chapter 6 you will learn about heat energy and its sources. Also, you will learn how heat affects matter and how it travels.

3. Section 6.1
What is Heat?

4. What is Heat? What happens when you hold an ice cube in your hand?
This is because your hand is ___________ than the ice cube.
Heat causes ice to melt.
Heat is a form of energy that results from the motion of particles in matter.
Heat energy flows from a warmer object to a cooler object.
Heat is a form of energy. Energy can do work. Therefore, heat can do work.
Steam Engine—burning fuel produces gases that make the engine work.
Car Engine

5. Sources of Heat
The faster particles move the more heat energy you have.
All matter is made up of atoms and molecules which are always moving.
This random motion and vibration of particles is a way to measure heat energy.

6. Sources of Heat: Sun
The sun is the earth’s most important heat source.
A heat source is a place from which heat energy comes.
Nuclear reactions in the sun are the source of heat energy that warms you.
Electricity is also a source of heat.
Example: Toaster—electric current passes through the wires of the toaster, the wires become hot.

7. Sources of Heat Other forms of energy can be changed into heat energy.
Example: hold your hands together and rub rapidly.
Friction between your hands a form of mechanical energy that produces heat.
Example: Oil well drills (mechanical energy) produce heat as they drill through rock. Workers must cool the drill with water to keep it from melting.
Chemical reactions sometimes produce heat.
Natural gas and other fuels burning produces heat.

8. Sources of Heat Nuclear energy is also a source of heat.
Nuclear energy is energy that is stored in the nucleus of the atom.
When the nucleus of an atom is split, the nucleus becomes smaller nuclei.
Energy is released in the form of heat and light.
The reaction is called nuclear fission.
Nuclear energy is also released when atoms are joined together.
When two nuclei combine they form a larger nucleus.
This reaction is called nuclear fusion.
Examples of nuclear energy: stars and sun.

9. How heat affects matter
Section 6.2
How heat affects matter

10. How Heat Affects Matter
Matter exists in different states.
In a gas the particles are typically far apart and move freely.
In a liquid the particles are close together but are still able to move freely.
In a solid the particles are close together and are not able to move past each other.
Heat causes particles to move faster and farther apart.
Heat can change from one state to another.

11. Changing from a Liquid to a Gas
What happens when you boil water?
Heat makes the water molecules move faster.
As the molecules move faster, they bump into each other more often and push each other apart.
As a result, the water evaporates (changes from a liquid to a gas).

12. Changing from a Gas to a Liquid
Frost forming on the inside of a window is an example of condensation.
The temperature outside is cooler than the temperature inside your home.
Condensation occurs when water vapor in the air returns to its original liquid state.
This happens the air cools and the temperature of the air drops.
The molecules in the air move at a slower speed.
Cold air cannot hold as much water vapor as warm air.
Some of the water vapor condenses to form tiny drops of liquid water.
Water drops that appear on a mirror after you have taken a hot shower are another example of condensation.

13. Changing from a Solid to a Liquid
What happens to an ice cube (solid) when it is left in a warm room?
Why does it melt?
Heat speeds up the vibrational motion of the molecules in the ice cube.
This motion disrupts the structure of the ice crystal.
The molecules are free to move around relative to each other.
The solid ice cube changes to liquid water.

14. Expanding and Contracting Matter
Heat causes particles in matter to push farther apart.
Then the matter expands, or becomes larger in size (It fills up more space).
Example: Metal Bridge—Summer heat makes the material in the bridge expand.
What could happen if the bridge did not have an expansion joint.
Solid, liquids, and gases do not expand equally.
Typically, liquids expand more than solids.
Gas usually expands the most.

15. Expanding and Contracting Matter
Sometimes matter loses heat.
Particles in matter move more slowly and stay closer together as they lose heat.
The matter contracts, or becomes smaller (It takes up less space).
Example: Bridge—the bridge contracts in cold weather.
Water: contracts until it reaches 4 degrees Celsius.
Water: Expands until it freezes at 0 degrees Celsius.

16. Section 6.3
Temperature

17. Temperature
What happens when you put your hand in a bowl of cool water?
Heat energy from your hand flows into the water and makes the water warmer.
The more your hand heats the water, the faster the water particles move.
Temperature is a measure of how fast an object’s particles are moving.
The higher the temperature, the faster an objects particles move.
Touching an object does not always give an accurate measurement of an object’s temperature.

18. Thermometers
How can you measure temperature accurately?
A thermometer is a device we use to measure temperature.
Examples: Traditional thermometer and electric thermometer.

19. Temperature Scales Two common scales are used to measure temperature.
Fahrenheit (F) and Celsius (C)
Scientists use the Celsius scale.
Temperature is always measured in units called degrees.
The symbol for degrees is ______ .
Any temperature below 0 is written with a minus (-) sign.

20. Temperature Conversion
If you know the temperature of a substance on one scale, you can convert to an equal temperature on the other scale.
Formulas:
F = 9/5 x C + 32 or F = 1.8 x C + 32
Example: C = 22. Solve for F.
C = 5/9 x (F - 32)
Example F = 48. Solve for C.

21. Freezing Point
What happens when you place a container of water in the freezer?
The water gradually changes to ice.
As the temperature of the water decreases, the water loses heat and eventually becomes a solid.
Freezing Point Celsius: 0
Freezing Point Fahrenheit: 32

22. Melting Point
The temperature at which a solid changes to a liquid is called its melting point.
The melting point of a substance is the same as it’s freezing as its freezing point.
The term melting point is used when a substance is being heated.

23. Boiling Point
The boiling point of a substance is the temperature at which it changes from a liquid to a gas under normal atmospheric pressure.
Boiling Point Celsius: 100 (Water)
Boiling Point Fahrenheit: 212 (Water)
Every substance has its own freezing and boiling points.
Scientists use the freezing and boiling points of substances to help identify unknown substances.

24. Changing Freezing Point and Boiling Point
You can change the freezing point and boiling point of a substance by mixing substances together.
Example: Adding alcohol to water causes the freezing point of the mixture to be lower than the freezing point of water alone.
Example: Antifreeze contains alcohol
This keeps water in the radiator from freezing which prevents engine damage.
Antifreeze also has a higher boiling point than water and boils more slowly than water in hot weather.
Certain compounds of sodium and calcium are used on icy roads and walkways in the winter.
These compounds lower the freezing point of water and change the ice back to a liquid.

25. Temperature and Heat Temperature and heat are different.
Temperature is a measure of how fast the molecules in a substance are moving.
The higher the temperature, the greater the atomic or molecular motion.
Heat depends on the temperature of a substance and the amount of matter, or mass, the substance has.
As the temperature of an object increases, the amount of heat in the object also increases.
If two objects of different mass are at the same temperature, the object with a greater mass will give off more heat.
Example: Lighted candle versus bonfire.

26. Section 6.4
How Heat Travels?

27. How Heat Travels
Think about different ways that you travel/move from one place to another.
Cars, bike, walk, run, train, boat, plane, etc.
Energy also has different ways of moving from warm matter to cool matter.

28. Radiation
The is 150 million kilometers from the earth yet the sun still heats the earth.
To do this the sun’s energy must travel through a vacuum.
A vacuum is a space which has no matter.
Energy from the sun reaches us by radiation.
Radiation can carry energy where there is no matter.
Radiation is the movement of energy through a vacuum.
Heat from sources other than the sun can also travel by radiation.
Example: Heat from a fireplace moving into a room.

29. Conduction Why does a strip of metal get hot when held to a flame?
The metal gets hot because of conduction
Conduction is the movement of heat energy from one molecule to the next.
Heat travels by conduction when molecules bump into each other.

30. Conduction Energy moves easily through some kinds of matter.
A substance that allows heat energy to flow through it easily is called a conductor.
Most metals are good conductor (copper, silver, gold, aluminum, and tin).
A material that does not conduct heat well is called an insulator.
Energy does not move easily through insulators.
Insulators are used in the walls of homes to heat out in the summer and keep cold out in winter.
Examples of insulators: glass, wood, sand, soil, Styrofoam, and air.

31. Convection
Convection is a method of heat movement that happens when the particles of a gas or liquid rise (as they rise they carry heat).
Example of a heater:
Convection also happens in liquids.
Example: Pot of water on a stove.
Warm water rises and cold water sinks.