Opening Remarks about Heat Capacity

Proposed Opening Remarks by a Teacher Introducing Heat Capacity

You could start out by mentioning a few very "heady" things - such as showing them Einstein's equation and then mentioning the need ALSO to be concerned about the conservation of energy equation. Then you can allow a little mental relaxation to occur when you tell them that there is an easier way to do heat capacity than dealing with Einstein's equation. NEVERTHELESS, they MUST still be concerned with the conservation of energy equation.

"Are you ready for this?" you ask the class. "Well here it comes, and you will all learn it in its greatest detail. Are you REALLY ready?" you ask to re-provoke their worrying. "Here it is:"

energy lost = energy gained

"Got it? Let me give you a quiz!" You point at someone in class: "Stand up and answer this in terms of the conservation of energy equation: you are out camping and you need to heat some water. All you have is a plastic bucket, which, of course, you cannot set on the fire. You half fill the bucket with stream water, and then, smartly, using sticks, lift a hot, clean rock from your campfire and drop it into the water. What happens to the water? Use the conservation of energy equation and tell why you answered as you did."

The kid should say that the hot rock heats the water, and that the amount of heat energy that leaves the rock equals the amount of heat energy gained by the water.

This should be obvious to all the students. The class mindset is established, and then you can enter into the fine details of the equation:

| (Δtemp_w x mass_w x C_{v_w}) | = | (Δtemp_x x mass_x x C_{v_x}) |

Remembering that:

You can move the terms around to get to the final equation:

C_rel = | (Δtemp_w x mass_w)/(Δtemp_x x mass_x) |

((This might be said to be in the line of pedagogical reasoning used by Noah Webster and McGuffy's Readers - add some practical relevance to what the kids are studying. Here it is learning how to apply what one learns in class to heating water while camping. Literally far afield!))