1. What is Heat?

2. Why did you put a jacket on this morning? What is cold? What is hot? Why are faucets labeled “H” and “C”? When you first turn on the “hot” water is it hot? Name something you would consider to be hot.

3. Isn’t it really cold compared to something like the sun? How about something you would consider cold? Isn’t it really hot compared to something like liquid nitrogen?

4. So what then is heat? Heat is the transfer of energy between objects at different temperature. Thermal energy always moves from higher energy to lower energy. So why do some things feel cold while others feel hot?

5. Things feel warm because the object that is touching you has more thermal energy than you do. That energy is transferred to you and you feel the extra energy as “heating up” or “warm”.

6. So why do some things feel cold while others feel hot? Things feel cold because the object that is touching you has less thermal energy than you do. That energy is transferred to the object and you feel the loss of energy as “cooling down or “cold”.

7. So what are we trying to describe when we use the words hot or cold? We are describing temperature. Temperature is the average kinetic energy of the particles (atoms and molecules) that make up an object.

8. Would it be possible to measure all of the kinetic energy in an object? Too many particles The energy is constantly moving from particle to particle because they collide. So how can we find the “average” kinetic energy? Temperature.

9. In 1593 Galileo invented the thermoscope which used glass bulbs of varying masses floating in water to determine the air temperature. In 1612 Santorio Santorio became the first to attach a scale to his thermometer. Neither were very accurate

10. Daniel Gabriel Fahrenheit 1686- 1736 Fahrenheit was a physicist, an engineer, a merchant, and more importantly a glass blower. His thermometers were of the highest quality for the time and were nearly identical to each other. So why do we use Fahrenheit’s thermometers?

11. 212⁰ boiling point of water Freezing point of water 0⁰ 100⁰ 20⁰ 40⁰ 60⁰ 80⁰ boiling point of water 32⁰ Freezing point of water 20⁰ 40⁰ 120⁰ 60⁰ 140⁰ 80⁰ 160⁰ 100⁰ 180⁰ 200⁰ 220⁰ 0⁰ Fahrenheit Celsius Centigrade scale

12. 212⁰ boiling point of water Freezing point of water 0⁰ 100⁰ 20⁰ 40⁰ 60⁰ 80⁰ boiling point of water 32⁰ Freezing point of water 20⁰ 40⁰ 120⁰ 60⁰ 140⁰ 80⁰ 160⁰ 100⁰ 180⁰ 200⁰ 220⁰ 0⁰ Fahrenheit Celsius Centigrade scale

13. 212⁰ boiling point of water Freezing point of water 0⁰ 100⁰ 20⁰ 40⁰ 60⁰ 80⁰ boiling point of water 32⁰ Freezing point of water 20⁰ 40⁰ 120⁰ 60⁰ 140⁰ 80⁰ 160⁰ 100⁰ 180⁰ 200⁰ 220⁰ 0⁰ Fahrenheit Celsius Centigrade scale

14. 0⁰ 100⁰ 20⁰ 40⁰ 60⁰ 80⁰ 20⁰ 40⁰ 120⁰ 60⁰ 140⁰ 80⁰ 160⁰ 100⁰ 180⁰ 200⁰ 220⁰ 0⁰ Fahrenheit Celsius Centigrade scale Weida 0⁰ -250⁰ 1350⁰

15. 0⁰ 100⁰ 20⁰ 40⁰ 60⁰ 80⁰ 20⁰ 40⁰ 120⁰ 60⁰ 140⁰ 80⁰ 160⁰ 100⁰ 180⁰ 200⁰ 220⁰ 0⁰ Fahrenheit Celsius Centigrade scale Weida 0⁰ -250⁰ 1350⁰

16. 0⁰ 100⁰ 20⁰ 40⁰ 60⁰ 80⁰ 20⁰ 40⁰ 120⁰ 60⁰ 140⁰ 80⁰ 160⁰ 100⁰ 180⁰ 200⁰ 220⁰ 0⁰ Fahrenheit Celsius Centigrade scale Weida 0⁰ -250⁰ 1350⁰

17. 0⁰ 100⁰ 20⁰ 40⁰ 60⁰ 80⁰ 20⁰ 40⁰ 120⁰ 60⁰ 140⁰ 80⁰ 160⁰ 100⁰ 180⁰ 200⁰ 220⁰ 0⁰ Fahrenheit Celsius Centigrade scale Kelvin 273.15 373 Absolute zero -273.15⁰ C -460 ⁰ F

18. So what then is heat? Heat is the transfer of energy between objects at different temperature. What type of energy is transferred? Thermal Energy

19. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

20. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

21. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

22. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

23. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

24. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

25. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

26. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

27. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

28. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

29. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

30. When objects of different temperatures come in contact, energy will always be transferred. Thermal energy will always pass from the warmer object to the cooler object.

31. This process is called thermal conduction. Substances that conduct thermal energy very well are called thermal conductors. Substances that do not conduct thermal energy very well are called thermal insulators.

32. Another way thermal energy can transfer is through the movement of a liquid or a gas. This is called convection. When you boil water in a pot, the water moves in a roughly circular pattern because of convection.

33. As the water on the bottom of the pot heats up it becomes less dense than the cooler water on top of it. The warmer water rises above the cooler water. The cooler water warms up and rises………………

34. Another way thermal energy can transfer is through radiation Radiation is the transfer of energy as electromagnetic waves. Radiation is what we feel when we put our hands near a heater or a hot stove.

35. Radiation is the transfer of energy as electromagnetic waves. Radiation is how sunlight reaches the Earth.

36. It is the radiated energy from the sun that warms the Earth. That energy is converted into thermal energy that helps warm the Earth. Most of that thermal energy is lost through radiation into space. That is why it is cooler at night. Our atmosphere traps some of the radiation through reflection. This prevents the extreme temperature differences you find on the moon (100°C on the lighted side and -173° on the dark side) or other planets.

37. The addition of “greenhouse gasses” increases the reflection of radiation. This causes the trapping of more radiation. This can lead to an increase in the temperature of the Earth.