TEMPERATURE. 2. How did your right hand feel (in terms of temperature) when it was placed in the room temperature water?

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1 TEMPERATURE Name(s) PART 1 WHAT TEMPERATURE IS IT? A) Obtain a bucket of hot water (but not so hot that it will burn your hand), a bucket of ice water, and a bucket containing water at room temperature. (In order to be sure you are using room temperature water, you should use water which has been sitting out in the room for several hours.) Place your left hand into the bucket of hot water, and place your right hand into the bucket of ice water. Leave both hands in these buckets for ten seconds. When time is up, immediately put both of your hands into the bucket containing room temperature water. Observe how this water makes your hands feel, and then answer the following questions. 1. How did your left hand feel (in terms of temperature) when it was placed in the room temperature water? 2. How did your right hand feel (in terms of temperature) when it was placed in the room temperature water? 3. Why do you think the room temperature water felt different to each of your hands? 4. What does this activity suggest to you about a human's ability to determine the temperature of things? B) Place your cheek against six different objects in the room. Your goal is to try and rank the objects according to their temperatures; starting with the one with the highest temperature, and going to the lowest. (You are asked to use your cheek because they are particularly sensitive to temperature variations.) After you have attempted to order the objects according to their temperatures, you should go back and actually measure the temperatures of the objects by placing the bulb of a thermometer against each one. Some materials you may wish to investigate include those made from wood, metal, and cloth. There is a table on the next page so that you may record your results. II-45

2 Object Touched Perceived Order of Temperature Hottest Coldest Actual Temperature What does this activity suggest to you about a human's ability to determine the temperature of an object? PART 2 A PARTICLE MODEL FOR HEAT It should be apparent from the preceding activities that our human senses can not be relied upon to accurately determine the temperature of objects. Fortunately, the particulate model of matter can be utilized to give a reliable definition for temperature. ACTIVITY #1 A) Obtain two small jars. Label them A and B. Fill A with very hot water, and fill B with ice water. Drop one drop of food coloring into each jar, and watch the drops spread out. 1. Based on your observations of the two jars of water, what would you say about the motion of the water molecules in the hot jar as compared to the motion of the water molecules in the cold jar? Now obtain two sugar cubes and place one into each jar. Stir the waters a bit and note which of the sugar cubes dissolves more quickly. II-46

3 2. Using a particle model, what is an explanation for the different rates at which the sugar cubes dissolved? ACTIVITY #2 1. If you shake a jar of water vigorously, what do you think will happen to the speeds of the water molecules? 2. If you shake a jar of water vigorously, what do you think will happen to the temperature of the water? You will try this water-shaking activity in a bit, but first, you will try it with sand. Obtain two dry jars, and fill them both about 2/3 full of sand. Carefully measure the temperatures of the sand in the two jars. Jar A Jar B Tighten a lid onto each jar. Wrap each jar with several layers of wrinkled newspaper, and secure the newspaper with tape. Shake jar A as hard as you can for 5 minutes without stopping. (Do not just slosh the sand around. Shake it with a hard, jerking motion.) Do not shake jar B, but have another person hold it as tightly as jar A is being held. You may trade positions with your partners if one of you gets tired before the five minutes are up. When the five minutes are up, quickly measure the temperatures of the sand in the two jars. 3. Did the temperature change in jar B? 4. If so, by how much? II-47

4 5. What do you think caused the change in temperature (if it did change)? 6. Did the temperature change in jar A? 7. If so, by how much? 8. What do you think caused the change in temperature? (If the temperature in your jar did not seem to change, check to see what result others in the class obtained.) Now repeat this activity by filling two small jars 2/3 full of room temperature water and shaking one of them vigorously for five minutes. Follow the same procedure as before in terms of using newspaper for insulation and making careful measurements of the water temperatures. Report on your findings below. In particular, compare the change in temperature of the water to the change in temperature of the sand which you found previously. Is this result consistent with what was found regarding the rates at which land and water heat up due to sunlight? Summarize your understanding of the relationship between the temperature of a substance and the motion of the particles making up the substance. II-48

5 PART 3 HEATING UP A GAS A) Reconstruct the physical model of a gas you made in the last section on Atomic and Molecular Motion by using marbles and a petri dish. Shake the dish slowly to simulate a gas at a relatively low temperature. Note how hard the gas particles are hitting against the walls of the dish. B) Now shake the dish harder to simulate a gas at a higher temperature. Again note how hard the gas particles are hitting the walls of the dish. 1. In which instance was the gas pressure greater, when the gas was at a low temperature or at a high temperature? (Explain your reasoning.) 2. Explain why a container of gas tends to expand as the gas inside gets hotter. C) Obtain an empty pop bottle and a balloon. Secure the balloon over the top of the bottle, and place the bottle in a container of hot water. Observe the balloon/bottle system until no more changes occur. D) Next, place the bottle into a container of ice water, and again observe the changes in the balloon and bottle system 3. Explain your observations of the balloon based on your particulate model of temperature. II-49

6 GAS THERMOMETER Many common thermometers are made of a hollow glass tube containing alcohol or mercury. When the thermometer is put into a warm substance, the liquid "rises" to a higher reading. A very sensitive thermometer can also be made using a gas instead of a liquid water A) Put a 1 cm "plug" of colored water in a clear plastic tube as shown in the diagram. B) Position the straw part way into a flask and seal the top of the flask with clay so that no air can go in or come out. C) Place your warm hands on the flask and observe the water plug. D) Place the flask into cold water and again observe the water plug. flask clay 1. Explain the observed motion of the water plug by describing the changes in the gas particles in the flask. 2. Some people think the liquid in a thermometer rises when the temperature goes up because "heat rises". Turn your thermometer upside down and show that heating the flask does not make the water plug rise. EGG IN THE BOTTLE The following classic egg-in-the-bottle teacher demo can be understood by pulling together particle ideas on pressure, temperature and motion. Find a fruit-juice jar and a peeled, hard-boiled egg that is just a little too large to fit easily through the top of the jar. Get a piece of paper (perhaps 8 inches by 2 inches), matches, and a tub of water. Think for a moment about fire safety. No one with long hair that is not tied back should handle a burning object. The tub of water is to drop burning materials into if necessary. Remove flammable materials from your work area. Light the paper on fire, drop it into the jar, and then place the egg on the top of the jar. Record your observations, and explain the events in terms of air pressure. Then, devise a means of getting the egg back out of the jar without destroying the egg. Describe your method. II-50