Item Description: In this activity, students are asked to test four materials and decide which would be the best for use as a heat mass. Students heat up the materials and then monitor heat loss over time. They then graph the temperature versus time of each of the substances and decide which material would make the best heat mass. A student's decision should be based on a combination of two factors: (1) how warm the material gets when heated and (2) how slowly the material cools down once the heat stops being supplied. These two factors are very much subject to a material's specific heat (or heat capacity). For any material there is a certain amount of heat required to raise the temperature. Materials with low heat capacity require very little energy to raise their temperature. This material would then tend to cool quickly as it would not have a large store of energy. Thus a good heat mass would be one with a low heat capacity. It would heat slowly during the day so that the home would not get hot too quickly, but it would also store a lot of energy with the low temperature change so that the heat would be given back to the house during the cool night. One other factor here is the ability to absorb heat by radiation (light). Water seems to have a low heat capacity because it warms very slowly, however, water is actually a very poor absorber of light. For this reason, it neither absorbs much energy or gets very warm. ME124 Rubric Criteria 1: Student draws graph which shows one of the materials at all times or all of the materials at one time. (Q1) OR Student lists one of the materials as being the best heat mass. (Q3) Criteria 2: Student's graph clearly and accurately shows all data. (Q1) OR Student chooses a material and uses any argument which agrees with his/her data (Q3). Example: Styrofoam cools faster. OR Student uses a defense which is correct (parameters in criteria three) but disagrees with data. For example, saying sand cools down the least when gravel does according to the data. Criteria 3: Student defends choice with idea (and data) that show the material cools down slowly (or keeps a constant temperature). (Q3) OR Student's defense uses idea of something heating up quickly to a high overall temperature. (Q3) Criteria 4: Student combines ideas of a material cooling slowly and having higher overall temperatures in defending their choice of heat mass. No specific substance is needed, although sand and gravel will be the most likely choices in this criteria. (Q3)