Temperature is a measure of the average kinetic energy of particles, with higher temperatures indicating faster particle motion. There are three main temperature scales: Fahrenheit, Celsius, and Kelvin. Fahrenheit and Celsius are used to measure temperatures experienced in daily life, while Kelvin is used for scientific purposes since it does not have negative values. Heat is transferred between objects through conduction, convection, and radiation. Conduction requires direct contact, convection occurs through fluid movement, and radiation transfers heat via electromagnetic waves.

1. Heat and Temperature Unit 28

2. Temperature Temperature is a measure of the average Kinetic Energy of the particles in a substance. Remember KE is the energy of motion. The higher the average Kinetic Energy, the faster the particles move Temperature and Heat are NOT the same thing View these sites for more on temperature Temperature and Temperature Scales Temperature

3. Temperature Scales There are 3 Types of Temperature Scales Fahrenheit Celsius Kelvin Celsius Fahrenheit

4. Fahrenheit Scale Most commonly used in United States. (originated in Great Britain) Non-metric system scale Not usually used in science Visit these “cool” web sites Converting between oF and oC Fahrenheit and Celsius Scales History of Fahrenheit Scale

5. How Fahrenheit Works Water freezes at 32°F Water boils at 212°F Zero was based on the lowest they could get water to stay liquid at the time (with salt in it). 100° was based on the highest it was believed humans could survive at the time

6. Celsius Scale Based on Metric System Scale Most used in the world, including Canada, Europe, and Asia Visit these “cool” web sites History of Celsius Scale Converting between oF and oC Anders Celsius

7. How Celsius Works Water freezes at 0°C Water boils at 100°F Absolute zero is -273°C

8. Kelvin Scale Actual Metric System scale. Most often used in Laboratory settings for calculation purposes. There are no negative temperatures. A change (Δ) of 1oC = 1 K. Converting from oC to K William Thomson Baron of Kelvin

9. Absolute Zero Defined as 0 Kelvin. Average temperature of space is 2.7K Scientists have gotten within fractions of absolute zero, but it is impossible to ever completely stop the movement of an atom, since that means it has zero energy. Boomerang Nebula contains the coldest known temperature in the universe at 1K Helium can only become a gas at below 5K

10. Temperature Scale Comparisons 373 K = 100°C 37°C = 99°F 298 K = 25°C 273 K = 0°C -40°C = -40°F 0 K = -273°C

11. Heat Transfer Conduction, Convection, and Radiation

12. Types of Heat Transfer

13. Conduction Takes place between solids or solids with liquids Particles vibrating or moving faster transfer some of their energy to nearby atoms

14. Conduction When particles collide and the faster ones pass some of their energy on to the cooler ones. This results in a change in energy for each particle This causes the faster ones to slow down and cool The slower ones speed up and heat up

15. Examples of Conduction Conduction requires direct contact

16. Convection Occurs in Fluids (liquids and gases) Caused by a change in density due to a change in temperature.

17. Convection con’t The warmer fluid expands, becomes less dense and rises. The cooler fluid contracts, becomes more dense and sinks.

18. Convection con’t Lava Lamps are an example of convection that you have probably seen before.

19. Importance of Convection Convection causes warm water vapor to rise, condense into clouds when it cools, and then falls back as rain Without convection, there would be no rainfall and thus no plants

20. Examples of Convection Magma in the mantle rises due to convection. The heat from the core heats it and then it rises to form volcanoes on the surface

21. Radiation The transfer of energy due to Infrared and other electromagnetic rays. Radiation can travel through space. All things radiate heat.

22. Why are light bulbs hot? They produce infrared radiation in addition to visible light Infrared transfers energy to the molecules that makes them vibrate faster (thus hotter)

23. Thermal Expansion When objects heat up their particles move faster, hit others harder, and bounce further, creating more empty space between the particles. As a result, the entire substance expands. This is known as thermal expansion

24. Examples of Thermal Expansion Roads crack as they expand in the heat On bridges and other sensitive sections, expansion panels allow it to flex.

25. Thermal Expansion continued The liquid in a thermometer expands as it warms. This causes it to head up the tube and tell you the temperature

26. Heat Transfer Heat Conductors Good thermal conductors transfer heat rapidly Metals are good thermal conductors Radiators are metals that transfer the heat in the water to the air Frying pans transfer heat from the stove to the food

27. Heat Transfer Thermal Insulators Poor thermal conductors of heat. Asbestos, cork, ceramic, cardboard, and fiberglass are examples of thermal insulators