UVA PHYS 635 - Heat And Temperature Worksheet

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Lab 14b - Heat and Temperature 245 ______________________________________________________________________________ University of Virginia Physics Department Physics 635, Summer 2009 Lab 14b: Heat And Temperature Worksheet Make sure the brass cylinder has been placed in the pot of boiling water. I. Mixing the same materials Material: 2 Styrofoam cups, 2 thermometers, sources of water at two different temperatures (hot and cold), digital balance, bucket to dump excess water. 1. We will be mixing water at various temperatures and determining experimentally the final temperatures of the water. You can use hot and cold tap water. Prediction 1-1: discuss with your group and write down below what you think the final temperatures of the following combinations of water will be: a) equal amounts at temperatures T1 and T2. b) unequal amounts by a factor of two at temperatures T1 and T2. Cup 1 has mass 2m at temperature T1 and cup 2 has mass m at temperature T2. 2. Now let’s discuss the experiment. Do not begin until instructed to do so here! Use two Styrofoam cups and the digital balance to determine the mass of your cups. Then obtain the water from your instructor and fill the cups no more than 1/3 full. Measure the mass of your cups until you obtain the amount of water you want. Measure the water temperature of each cup with a thermometer. In a minute you will pour the cold water into the cup of hot water and will need to read the temperatures of both thermometers until they come to equilibrium. When you are ready, you may begin. You will need to do both experiments described in 1a and 1b. Describe in your journal what happens. Do your experimental results agree with your predictions?246 Lab 14b - Heat and Temperature ______________________________________________________________________________ University of Virginia Physics Department Physics 635, Summer 2009 1a Equal Amounts at Temperatures T1 and T2 Mass of Cup: Mass of Cup: Mass of Cup + Hot Water: Mass of Cup + Cold Water: Mass of Hot Water: Mass of Cold Water: T1: T2: T1+2: Question 1-1: What happened? Do your results agree with your prediction? Discuss. 1b Unequal Amounts by a Factor of 2 at Temperatures T1 and T2 Mass Cup: Mass Cup: Mass Cup + Hot Water: Mass Cup + Cold Water: Mass Hot Water: Mass Cold Water: T1: T2: T1+2: Question 1-2: What happened? Do your results agree with your prediction? Discuss Question 1-3: Use your results to formulate an equation to predict the final temperature T of mass m1 of water at temperature T1 mixed with mass m2 of water at temperature T2.Lab 14b - Heat and Temperature 247 ______________________________________________________________________________ University of Virginia Physics Department Physics 635, Summer 2009 II. Mixing different materials Material: tongs, digital balance, Styrofoam cup, hot metal object, room temperature water, thermometer. Prediction 2-1: Predict what would happen if you placed a piece of hot metal into a cup of room temperature water of the same mass. How will the temperatures of each material change? Discuss this with your group and write your prediction below. 1. Follow the directions of your instructor, which may be different than given here. You should have already placed the 88.6 g brass cylinder in the boiling water so that it has reached thermal equilibrium. Measure an equal amount of room temperature water in a large Styrofoam cup. Remember to take account of the mass of the cup. 2. Place the thermometer in the cup and measure the temperature. You will be placing the hot metal object into the cup of water and measuring the temperature. You do not want to lose heat to the outside surroundings. Is there anything you can do to prevent this heat loss? Carefully using the tongs, grab the hot piece of brass from the boiling water, shake off the water on the brass, briefly wipe the excess water off with a paper towel, and place the brass cylinder carefully into the cup of water. Stir and measure the temperature of the water often. Record the temperature when it is constant; it will take a few minutes. 2 Equal Amounts of Different Materials at Temperatures T1 and T2 Mass Cup: Mass Brass Object: Mass Cup + Water: Mass Water: Tw: Tb: Tw+b:248 Lab 14b - Heat and Temperature ______________________________________________________________________________ University of Virginia Physics Department Physics 635, Summer 2009 Question 2-1: What happened to the temperature of the metal object during the experiment? Was the final temperature of the water consistent with your prediction? Explain why or why not. Question 2-2: Does the formulation you made in Question 1-3 apply in this case? Why or why not? If not, formulate another relation that predicts the final temperature for the present experiment. Question 2-3: Now let's determine the specific heat of the brass cylinder. Assume the initial temperatures of the water and brass are Tw and Tb, respectively, and the final temperature of the water is T. The heat lost by the brass is mbcb∆Tb where ∆Tb is the temperature lost by the brass, Tb - T. The heat gained by the water is mwcw∆Tw where ∆Tw is the temperature gain by the water, T - Tw. Now it should be easy to determine the specific heat of brass cb. Compare your experimental value with the accepted value of 0.092 cal/(g


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UVA PHYS 635 - Heat And Temperature Worksheet

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