Data Analysis and Concept Development

1. State the relationship for the three graphs.

2. Write the relationship as an algebraic formula.

3. Suppose you were given 205 mL of 30.0°C water that is mixed with 101 mL of 75.0 °C water, what is the final temperature of the mixture?

4. Assuming that the temperature of water in the coffee urn or insulated cooler didnÕt change, find the per cent error.

5. How good was your precision and accuracy in your originally designed experiment?

6. How could or did you design the procedure to improve accuracy?

7. Suppose you mixed 105 mL of 15.0 °C water with 70.0 mL of unknown temperature, and the final temperature of the mixture reached 43.0 °C. What was the initial temperature of the hotter water?

Reference This activity was originally developed at SUNY Cortland; this version was enhanced by John Ricketts of DePauw University.

Implications and Applications

Mixing liquids of different temperature and predicting the final temperature is an everyday phenomenon. We do it when we add milk to our coffee. Whenever there is a power plant and also in many factories, waste heat is removed through cooling water that is dumped into the environment, often into a passing stream or river. This leads to a temperature increase, often one leading to serious ecological consequences.

Heat is exchanged between two large bodies of different temperature that are brought into contact. In countries where malnutrition abounds, breast milk is often the only source of energy for a baby. However, the mother also provides heat while nursing (and at other times) that reduces the babyÕs total energy needs.

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