1. Temperature, Thermal Energy, and Heat
Chapter 13
Temperature, Thermal Energy, and Heat

2. What determines the Temperature of an Object?
Temperature is a measure of how hot or cold something is compared to a reference point.
One reference point is the freezing point of water.
Temperature is a measure of the average kinetic energy of the particles in an object.

3. Different Scales
Fahrenheit Scale= measure of temperature in the United States.
Celsius Scale= other countries use the Celsius Scale. Both the Fahrenheit and Celsius Scale are measured in degrees.
32 degrees Fahrenheit and 0 degrees Celsius are the freezing points of water.

4. Different Scales
Kelvin Scale- many scientists us the Kelvin Scale. The Kelvin Scale is divided into kelvins(K). A temperature change of 1 K is the same temperature change as 1 degree C.
Zero kelvins, or absolute zero, is the lowest temperature possible.
At absolute zero particles have no kinetic energy.

6. What is Thermal Energy?
Thermal energy is the total energy of all the particles in an object.
Thermal energy depends on the temperature of the object, the number of particles in it, and how those particles are arranged.
The more particles an object has at a given temperature the more thermal energy it has.

8. Particles move as thermal energy is added

10. Heat
You may say an object contains heat, but, strictly speaking, it does not. Objects contain thermal energy.
Heat is the transfer of thermal energy from a warmer object to a cooler object.
Heat will move from a warmer object to a cooler object until both object have equal thermal energy.

11. How does heat move?

12. How is heat transferred?
Heat is transferred from warmer areas to cooler areas by conduction, convection, and radiation.

13. Convection
Convection is a type of heat transfer that occurs only in fluids, such as water and air.
When air is heated, its particles speed up and move father apart. This makes them less dense.
The heated air rises to float to the top of the denser, cooler air.
As the cooler air heats, it moves upward and it pushes the cooler air down. This is called a convection current.
The same principals apply in fluids such as water.
Have you ever wondered why the water at the bottom of a swimming pool is cooler than the water at the top?

14. Convection

15. Convection

16. Radiation
Radiation is the transfer of energy by electromagnetic waves.
Radiation is the only form of heat transfer that does not require matter (medium).
You can sit next to a camp fire and feel the heat of the fire without touching the flames. This is radiant energy.
The sun’s heat travels through a vacuum(open space) millions of miles to warm the earth. This is an example of radiant energy.

17. Radiation

18. Conduction
Conduction transfers heat from one particle of matter to another within an object or between two objects.
The fast moving particles in the floor of the oven collide with the slow-moving particles in the uncooked pizza. This causes the pizza’s particles to move faster, making the pizza hotter.

19. Conduction

20. Thermal Properties
Some materials we use are Conductors and Insulators.
A conductor is a material that conducts heat well. Metals such as silver are good conductors.
Insulators are materials that do not conduct heat well. Other good insulators include air and wool. For example, wool blankets slow the transfer of heat out of your body. Hence you stay warmer throughout a cold night.

22. Thermal Expansion
To loosen a jar lid, you can hold it under a stream of hot water. This works because the metal lid expands more than the glass does as it gets hotter.
As the thermal energy of matter increases, its particles usually spread out, causing the substance to expand.
The expanding of matter when it is heated is known as thermal expansion.

23. Thermal Expansion

24. Thermal Expansion