Thermal Energy and Temperature Lab. Experiment Question: How can the difference between thermal energy and temperature be experimentally observed?

Transcription

1 Thermal Energy and Temperature Lab Name 7 th Grade PSI Grade / 20 Experiment Question: How can the difference between thermal energy and temperature be experimentally observed? Hypothesis Starters: 1. What is temperature? 2. Do all substances have the same amount of thermal energy at the same temperature? Explain your thinking. 3. What factors influence the amount of thermal energy an object has? Purpose: During this experiment, you will explore the difference between thermal energy and temperature. Often people think of temperature as being a measure of how much energy something has, but this is not the case. Temperature is related to energy but takes additional factors into account. If there are two objects that have the same amount of energy, they may have different temperatures if one has twice the mass of the other. In that case, each molecule would only have half as much energy, so the temperature is

2 lower. Other factors also play a role as you have hopefully already discussed in your hypothesis starters. In this experiment, you will observe how temperature changes as water transitions between its three phases: solid ice, liquid water, and water vapor. Pay close attention to when the temperature rises and when it remains constant. Also, since you will be adding energy to make the phase changes happen, be careful not to get burned. Materials: For each person: Safety goggles Apron (optional) For each group: One heat source (hot plate, Bunsen burner, or candle) Matches or lighter (if using Bunsen burner or candle) One thermometer (non-mercury for safety and a digital thermometer is preferred) One test tube and test tube holder (if using the Bunsen burner or candle) One small flask or beaker and a pair of tongs (if using the hot plate) Crushed ice Tap water Balance or scale Clock, stopwatch, or other timer Safety: You are dealing with heat sources and hot glassware. Use the test tube holder or tongs to hold the hot glass. If you are using a flame, make sure long hair is pulled back and avoid loose fitting clothing. Never point a container that is heating at someone. Make sure it is pointed away in a safe direction in case something splashes out. Procedure: 1. Gather all materials and read all directions before getting started. 2. Add crushed ice to the test tube, flask, or beaker. If you are using a candle as your heat source use between 2.0 g and 3.0g of ice. If you are using a Bunsen burner or a hot plate, use between 15.0g and 20.0g of ice. 3. Place the thermometer so that it is down in the ice in your container. 4. Add enough tap water to cover the bulb of the thermometer or if you are using a digital thermometer, add enough water so that about 1.5cm of the tip is under water.

3 5. Once the temperature stabilizes, record the temperature of the ice/water mixture and record this as the time 0.0 minutes temperature on the data table or in your lab notebook. 6. Turn on your heat source and start heating the ice water mixture. (Set hot plates to medium high power.) 7. Every 20 seconds until enough water has boiled away that the thermometer is not able to give an accurate reading, make a measurement of the temperature and record it in the data table. REMINDER: Do not let your thermometer bulb touch the bottom or sides of the glass while you are heating. The glass should be hotter than the water inside. That is what causes the energy to flow. 8. When the ice has completely melted, put an M beside that time in the data table. 9. When the liquid begins to boil put a B beside that time in the data table. 10. When you can no longer accurately measure the temperature, turn off your heat source. 11. Clean up your laboratory station and return all materials to their proper locations.

4 Graphing Results: Using the results from your data table, draw a graph of temperature (vertical axis) versus time (horizontal axis). Be sure to include units on your axis labels. Using a different color than you used for the data points, connect the data points to form a curved shape. Use the graph to help you answer the Laboratory Questions below. Laboratory Questions: On a sheet of paper or in your laboratory notebook, answer the following questions about the experiment. 1. What happened to the temperature of the mixture as the ice melted? 2. What happened to the temperature of the liquid water after it was done melting but before it started boiling? 3. What happened to the temperature of the water while it boiled? 4. Did your heat source ever stop giving energy to the water? 5. If all of the energy from the heat source was absorbed by the water, how do you explain why the temperature did not change significantly during each of the phase changes? Conclusion: On a sheet of paper or in your laboratory notebook, write one or two paragraphs that summarize the experiment results and cover the following key points. 1. Explain in your own words how the experiment shows that temperature and thermal energy are similar but not the same thing. 2. Explain what happened to temperature in each of the three time periods: Melting, Heating, and Boiling. 3. Explain whether this is an endothermic or an exothermic process.

5 TEMPERATURE RESULTS DATA TABLE Time (seconds) Temperature (degrees Celsius) Time (seconds) Temperature (degrees Celsius)