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# Thermodynamics: Energy Transfer

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Author: Janice VanCleave

Your daily life brings you in contact with hot and cold objects. You observe that iced drinks get warmer and hot drinks get cooler. These everyday experiences can be explained by thermodynamics, the study of energy movement. Thermodynamics is from the Greek word thermos, which means "heat," and dynamics, which implies movement.

In this project, you will determine the direction of energy transfer of two materials. Calculations of heat content will be made. You will study the effect that a substance's specific heat has on the amount of energy needed to change the temperature of the substance, and you will also determine the specific heat of a substance.

### Getting Started

Purpose: To determine the direction of energy transfer when two materials of different temperatures are placed together.

### Materials

• 2-quart (2-liter) metal teakettle with lid
• water
• stove
• l-quart (l-liter) bowl
• thermometer
• ruler
• scissors
• string
• 3 stainless steel nails (16-penny size)
• tongs

### Procedure

1. Fill the teakettle three-fourths full with water and heat it.
2. While waiting for the water to boil, fill the bowl half full with cold tap water.
3. Use the thermometer to measure the temperature of the cold water in the bowl. Record this temperature as the initial temperature of the water.
4. Measure and cut a 12-inch (30-cm) piece of string.
5. Tie the nails together with one end of the string.
6. Lower the nails into the kettle of boiling water so that the nails are positioned in the center of the water.
7. Lay the string over the top of the kettle and close the lid. Note: The lid should hold the string stationary with the nails suspended in the water (see Figure 28.1).
8. Heat the nails for five minutes. The metal in the nails will heat to the temperature of the boiling water, which is 212°F (100°C). Record this temperature as the initial temperature of the metal.
9. Use tongs to move the nails from the boiling water.
10. Shake off as much of the hot water as possible from the nails and immediately immerse the nails into the bowl of cold water.
11. Gently stir the water with the thermometer (see Figure 28.2).
12. Observe the temperature of the water in the bowl. When the water reaches a constant temperature, stop stirring and record this temperature as the final temperature for both the metal and the water.
13. Calculate the change in temperature of the metal and the water by taking the absolute difference (subtracting the smaller from the larger number) between the initial and final temperatures of each. See Appendix 1 for an example calculation.
14. Construct a data table such as the one shown here.

### Results

The exact change of temperature of the water and the metal depends on the amount and initial temperature of the water in the bowl. Other factors affecting the temperature changes of materials will be studied later, but, in this experiment, the metal makes the greater temperature change.

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