Specific Heat Activity

Transcription

1 Title of Lesson Subject Area Age or Grade Level Specific Heat Activity Understanding energy transfers within the lense of specific heat 7 th grade This lab is designed to be an easy way to teach students the concept of specific heat. This is meant to be a follow up to lessons about types of energy, energy conversions, and basic energy transfers. Brief Overview Students will measure the temperature of water and sand within two beakers over one class period. Both beakers will be under a heat lamp. 15 minutes in the heat lamps should be shut off. This way the first 15 minutes should show an increase of temperatures in both (albeit at different rates) and the second 15 minutes will show a decrease in temperatures (again, at different rates). See Attached documents for a detailed methodology of lab experiment and analysis & calculations. Estimated Time Standards/Unit Goals Essential Questions Skill Objective(s) By end of this lesson, students will be able to Knowledge Objective(s) By end of this lesson, students will know 2 classroom days. One day for the lab and the 2 nd class day dedicated to discussion the analysis questions and graphs. Homework is assigned from the 1 st day to the second day which is also discussed on the 2 nd day..have the students understand the concept of specific heat and how it is in an individual material propterty. 1) What is the specific heat capacity of water? 2) What is the specific heat capacity of sand? 3) Which sample, sand or water, had the highest change in temperature during heating? 4) Which sample, sand or water, had the lowest change in temperature during heating? 5) Describe what happened during the heating of water compared to the heating of sand. 6) Describe what happened during the cooling of water compared to the cooling of sand. Understand the concept of specific heat, and the idea that it is an individual material property. Students will graph a short time-series of data. In this case the change of temperature over time (~30 minutes) - Specific heat vocabulary. - More precise and accurate measurement skills.

2 Materials Needed ml beakers - Thermometers - sand sample (to fill 150 ml per beaker) - water (~150 ml per beaker) - triple beam or electronic balance watt light bulb or heat lamp - stopwatch - Technology Tools Used Useful Vocabulary. New Vocabulary Word 1 Specific Heat Prerequisite knowledge/skills Understanding of types of energy, energy conversion, and methods of energy transfers. Anticipated Student Preconceptions/Misconceptions Instructional Tips/Strategies for the Teacher Students will have a hard time grasping the concept of specific heat at first. Before the lab, have a short discussion about which material (sand or water) will heat up faster or cool down faster. Opener. Introduce the lab and have students review the lab procedures. Have the students create a hypothesis of how much each material (sand or water) will heat up and cool down. Do not guide the students to any one particular answer. Development Day 1: Start the laboratory experiment detailed in the methodology. After the first 3 measurements (~2 minutes) have the students start discussing the graphs they will create. Have them draw rough graph sketches on page 4. Lesson Sequence The second set of measurements occur at minutes with the light being turned off at 15 minutes. Between 15 min and 29 minutes pass out the graphing sheets and have the students start graphing data. Whatever is not finished should be assigned as homework. Homework for night 1 is analysis questions 4-7 and finishing the graph. Development Day 2: Day 2 of this lesson should be devoted to discussion and deconstruction of the previous days data collection. Start off by analyzing the graphs (given as homework the previous day) and making sure all of the axis, vairiables, titles, etc are correctly done. Have the students describe and discuss the trends of the graphs of sand and water. This should lead into a discussion about specific heat values (table on page 3). Have the students try and describe

3 different every day materials in terms of specific heat. The rest of the class (~15) should be devoted to finishing up the data analysis questions. In particular, #10 should be written as a letter to a factory/pan company president. Resources Weblinks Reproducible Materials References Assessment Closure: Have students deconstruct the lab experiment and come to a overall conclusion. As a class discuss the variations in graphs observed and the possible reasons why the different temperatures might have occurred (external factors can play a large effect here) See attached pdf below Students should be graded on their letters written (in answer to question #10). This question should require a whole understanding of speicifc heat and it s day to day applications. Have some of the students read out their letter (emphasizing presentation skills) and have the class critique them. Extensions/Explorations Reflections Contact Information

4 Science 8 Specific Heat Lab Grade Level- Lab Activity Problem: How do the specific heat of sand and water affect how quickly water and sand heat up and cools down? Background Information: If you ve ever hiked up a mountain, walked barefoot on a sandy beach, or taken a summer vacation, you know that the Earth does not heat evenly. How quickly the ground or water heats during the day and cools during the evening is a function of specific heat of the ground or water. Specific heat is the amount of energy required to increase the temperature of a substance 1 C. If matter has high specific heat, it warms more slowly but holds heat longer than matter with low specific heat. Materials: ml beakers 2 thermometers sand sample water triple beam balance reflector light 2 pieces 4x4 cardstock 2 ring stands 2 ring clamps 100 watt light bulb Part A Directions: Complete the following in your composition book. Photo 1 Hypothesis: If, then. Complete your chart based on the experiment. Independent Variable (IV) Constants Dependent Variable (DV) 1

5 Part B: Create a Data Table in your comp book for 15 minutes of heating and 15 minutes of cooling: Time (minutes) Temperature of Sand ( 0 C) Temperature of water ( 0 C) Heating Cooling (turn light off) Part C: Procedure for collecting data: 1. Fill one 250 ml beaker with 150 ml of sand. 2. Fill one 250 ml beaker with 150 ml of water. 3. Insert thermometer through the cardstock so that it is suspended into each beaker. 4. Set up the lab equipment as shown in Photo 1. The thermometers should be suspended in the substances and should not rest on the bottom of the beakers. 5. Place the light so it is equal distance to the two samples. Turn light on. Turn on timer. 6. Take the temperature of each beaker every minute for 15 minutes. 7. Using the timer, turn light off after 15 minutes. Leave the remainder of the experiment unchanged. 8. Record the temperature of each beaker every minute for 15 minutes (minutes 16-30). Procedure for calculating data: 9. Use the triple beam balance to find the mass of the empty 250 ml beaker to the nearest tenth of a gram. 10. Fill one 250 ml beaker with 150 ml of sand. 11. Fill one 250 ml beaker with 150 ml of water. 12. Use the triple beam balance to find the mass of the sand and water. Record the mass in grams on the data table. Make sure to subtract the mass of the empty 250 ml beaker. 15. When the experiment time is over, record all data on the data table below. 16. Remove thermometers from beakers and wipe clean. 2

6 Look at the table below. Notice the difference in heat capacity of the items listed. Specific Heat Capacity Substance Specific Heat Capacity J/g ( 0 C) Wood Gold Glass Alcohol Water Sand Copper Note: (J) Joule is the amount of energy it takes to lift an apple 1 meter! Part D: Data Analysis Directions: Answer the following questions, using complete, reflective sentences in your comp book. 1. Graph your data on the graph paper. Remember, you are looking at the change in temperature over a 30 minute period. 2. What is the specific heat capacity of water? 3. What is the specific heat capacity of sand? 4. Which sample, sand or water, had the highest change in temperature during heating? 5. Which sample, sand or water, had the lowest change in temperature during heating? 6. Describe what happened during the heating of water compared to the heating of sand. 7. Describe what happened during the cooling of water compared to the cooling of sand. 8. If an element has a high specific heat, it takes energy to change its temperature. 9. If an element has a low specific heat, it takes energy to change its temperature. 10. You have been hired as a director of a frying pan production company, because of your knowledge of specific heat capacity. The president of the company believes that the company could save millions of 3

7 dollars a year by removing the plastic coating on the frying pan handles. Write a letter to explain to the president of the company why you should/ or shouldn t continue to use plastic for the handles. Copper has a specific heat capacity of J/g ( 0 C), and is used for producing the base of frying pans. A plastic used for a frying pan handle has a specific heat capacity of 1.5 J/g ( 0 C). Comparing data of different groups: 11. How does the data collected compare to the data collected by other groups? 12. Why aren t the results identical for all groups? The small changes in an experiment that affect results are called sources of error. What could be sources of error in this experiment? How well did your group control the constants you listed? Explain your answer. 4

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