Temperature and KE Lab 8th th Grade PSI Science Score /23. Part I: Kinetic Energy

Transcription

1 Temperature and KE Lab 8th th Grade PSI Science Lab Name Score /23 Part I: Kinetic Energy Objective: Investigate how the motion and spacing of water molecules differ in hot water versus cold water. Predict: Which will change color the fastest when food coloring is added: hot water or cold water? Explain your prediction. Materials: hot water in a clear cup* cold water in a clear cup* food coloring * You can use any amount of water between ml, just be certain to use the same amount of water in each cup. Procedure: 1. At the same time, put the same amount of food coloring (1-2 drops) in each cup of water. 2. Without disturbing the water, carefully observe what happens and write these observations down in the following table. Water Observations Cold Hot

2 Analysis: 1. Describe the differences in how the colors moved and mixed in the hot water versus the cold water. 2. Was your prediction correct? 3. What do your observations tell you about the speed of the water molecules in the hot and cold water? 4. Draw a model to represent the molecules in the hot water and the cold water. Use circles to represent the molecules and consider how spaced apart the molecules should be in each model. Circle whether the molecules move fast or slow. Cold Water: fast or slow Hot Water: fast or slow

3 5. The following is a list of variables in this experiment. State whether this variable was the same for each cup or different. Explain why it was important to either keep the variable the same or make it different in this experiment. Variable Same or Different Explanation Amount of water Drops of food coloring When the food coloring was added to the water

4 Part II: Building a basic thermometer Objective: Investigate how a thermometer works and relate it to the spacing and motion of molecules. Predict: Which takes up more space: hot or cold water? Materials: Safety goggles Clear plastic bottle with a narrow neck Isopropyl Alcohol Food coloring Tap water funnel Long clear plastic straw Modeling clay Marker Paper towels large bowl of ice cold water large bowl of warm or hot water Procedure: 1. Put on your safety goggles. 2. Pour equal parts of water and alcohol into the bottle using the funnel. Only fill about ¼ of the entire bottle with this mixture. 3. Add a couple of drops of food coloring to the water and alcohol mixture. Put the lid on the bottle and shake it to distribute the food coloring. 4. Uncap the bottle and drop the straw in. 5. Plug the opening of the bottle with the clay. See diagram below. modeling clay clear straw alcohol, water and food coloring

5 figure from energquest.ca.gov 6. Now that your rudimentary thermometer is finished, let it sit for several minutes undisturbed on your desk to bring it to room temperature. 7. Using your marker, draw a horizontal line level with the liquid level in the straw and label this room temperature. room temperature 8. Place your thermometer into the bowl with cold water. Observe what happens to the liquid in the straw and write these observations down in the following table. 9. Take your thermometer out of the cold-water bowl. Use a paper towel to dry it off before placing it into the bowl with hot water. Once in the hot water, observe what happens to the liquid in the straw and write down your observations. Bowl Observations of liquid in the straw Cold water Hot water

6 Analysis: 1. Describe how the liquid level changed relative to its level at room temperature when you placed the thermometer in the COLD water. Explain why this happened using what you know about how molecules move in COLD liquids. 2. Describe how the liquid level changed relative to its level at room temperature when you placed the thermometer in the HOT water. Explain why this happened using what you know about how molecules move in HOT liquids. 3. Based on your observations, state the relationship between the temperature of a liquid to its volume. 4. Suppose you repeated this experiment but instead of using a mixture of water and alcohol in your thermometer, you used mercury. Mercury consists of molecules with a higher attraction to one another. How do you think your observations would differ?

7 Part III: Measuring Temperature Objective: Measure water temperature using a standard thermometer and convert between the three scales of temperature. Predict: Before each temperature measurement, hypothesize what the temperature will be in Celsius. Materials: Celsius thermometer hot water in a clear cup* cold water in a clear cup* * Any amount of water can be used. Procedure (for each temperature measurement): 1. Predict the temperature in Celsius and record this value. 2. Measure the temperature by placing the thermometer undisturbed in the liquid or environment you are measuring. 3. Wait until the liquid level in the thermometer is stable and record the temperature in C in the table below. 4. Convert each measured temperature to Fahrenheit and Kelvin and record. Environment Hot water Predicted Temperature ( C) Measured Temperature ( C) Converted Temperature ( F) Converted Temperature (Kelvin) Cold water Classroom Outside

8 Analysis: 1. Describe how you came up with your predicted temperature values. 2. Were your predictions close to the measured values? Why or why not? 3. Show your mathematical work for your conversion to Fahrenheit and Kelvin for ONE environment here. 4. Compare your measured values with another group. Are they the same or different? If they are different, explain possible causes for the differences.