Heat and Thermal Energy

Heat and Thermal Energy Study Guide

26. What is “temperature”?

Temperature is one way we measure how much kinetic energy the particles WITHIN a substance has. It is the average measurement.

27. What do we mean by “the average kinetic energy of the particles of a substance?” What is kinetic energy? How do we find an average?

The average is found by adding together all of the kinetic energy of each of the particles, and then dividing by the number of particles. So, the average is a number that shows, in general, how much kinetic energy each particle has.

28. What are the three scales (languages) we can use when we talk about temperature?

Celsius, Fahrenheit and Kelvin

29. The Celsius scale was developed based on the freezing point and boiling point of water. Water freezes at zero degrees Celsius and boils at 100 degrees Celsius.

30. The Kelvin scale was developed with the idea that “zero” should mean no kinetic motion. This special number that means that the none of the particles in the substance are moving at all is called what?

Absolute zero is what we call 0 Kelvin. It means that none of the particles, and no part of the particles (like the electrons) is moving.

31. What is thermal energy?

Thermal energy is another way of measuring the kinetic energy within a substance, but this time, it means the total amount of energy.

32. How is thermal energy different from temperature?

Thermal energy is the total amount of energy, so it would be adding together all of the energy of all of the particles. Temperature is the average amount of kinetic energy, so you would start off by adding the energy of the particles, but then you would divide by however many particles there are, so that you end up with one number that tells you, in general, how much energy each of the particles has.

33. Which would have a higher temperature, a pot of boiling water, or an iceberg? Explain your answer. the pot of boiling water; each of the particles in the pot of boiling water would be moving more than each of the particles in the iceberg.

34. Which would have more thermal energy, a pot of boiling water, or an iceberg? Explain your answer. the iceberg would have more thermal energy, because even though each particle has a lot less kinetic energy, there are so many more particles in the iceberg that when you add them all together, it comes out higher

35. If you had equal amounts of water, ice and steam in jars, which would have the highest amount of thermal energy?

Steam would have more thermal energy. Let’s look at it this way: let’s say there were 10,000 particles in each jar (equal amounts). The particles in the solid (ice) would be moving the least... we’ll say each one has a value of 1, so altogether, they would have a thermal energy of 10,000 (10,000 times 1). Let’s say each of the particles in the liquid (the water) has a value of 5, because, of course, the particles in liquids are more active than the particles in a solid. So, the thermal energy in the liquid is 10,000 times five, or 50,000. The particles in a gas are bouncing around everywhere. Lots of energy. So, we’ll say each of the particles has a value of 10. To find the thermal energy, we’d add ten 10,000 times... or we can take a shortcut and say 10,000 times 10. This would be 100,000. So, if they all carry the same number of particles, then steam would have both higher temperature AND higher thermal energy.

36. Use this graph to answer questions 37-44. 37. At point A, what state or state of matter is the matter in? solid (not ice! this is not water!)

38. At point B something different happens. What is it? the solid melts and starts to become a liquid

39. At point C, the substance starts changing again. What state or states of matter is the substance in, between points C and D? it is a liquid, and the liquid is heating up --- that’s why the line on the graph starts rising again

40. Point D starts another change of state. What is it called? at point D the substance is vaporizing – going from a liquid to a gas

41. What state or states of matter is the substance in, between points D and E? part of it is a liquid and part a gas. At D it is a lot of liquid and little bit of gas, but, as more energy is taken in, more and more of it turns to a gas; but the temperature doesn’t rise until ALL of it has turned to gas

42. Right after point E on the graph, what state or states of matter is the substance in?

It is a gas, increasing in temperature.

43. What is the melting point of the substance? What is the boiling point? How did you know?

The melting point is about 70 Celsius and the boiling point is 140 Celsius. We know this because 70 is where the substance starts turning into a liquid and 140 is where it starts to turn to a gas.

44. Summarize the graph in three sentences.

As particles take in energy, they become more active. When all of the particles are in the same state, and they take in more energy, the temperature goes up. But, when the particles change state (go from one state to another) the temperature doesn’t go up.

Section 4- Heat and Heat Transfer 45. What is heat?

Heat is when thermal energy goes from one substance to another. Thermal energy, in nature, goes from areas where there is more of it, to areas where there is less of it. The energy that is exchanged in this transfer is known as heat.

46. What is thermal equilibrium? When thermal energy moves from one place to another it tries to create a balance – to make each substance equal in thermal energy. This is called thermal equilibrium.

47. What is conduction? Give an example.

When thermal energy moves from a solid to another substance. When you touch a hot skillet and it burns you, that is conduction.

48. What are conductors and insulators?

Conductors allow thermal energy to move easily through them. Insulators tend to trap thermal energy, and don’t allow it to move.

49. Label the items properly as either conductors or insulators.

Conductor or insulator? copper pipes conductor oven mitt insulator sweater insulator baking sheet conductor bottom of frying pan conductor handle of frying pan insulator

What do all of these conductors have in common? they are all metals. metals tend to be good thermal energy conductors.

50. What is convection? Give an example.

When thermal energy moves from a liquid to another substance. When you put ice cubes into soda, the thermal energy moves from the soda to the ice cubes. This is convection. Also, any food you boil is cooked by convection.

51. What is radiation? Give an example.

When thermal energy moves by electromagnetic waves, like the sun heating the earth, or a campfire warming you.

52. In general, thermal energy tends to move from areas with more thermal energy to areas with less thermal energy.

53 . A refrigerator keeps the inside cool by having thermal energy go from areas with less thermal energy to areas with more thermal energy.