Some Like it Hot Part I: By the Beautiful Sea 1) Imagine you were to place a thermometer in a pot of water and heat it to boiling, how would you expect the graph of temperature versus time to look for this situation. Draw your prediction on the graph below. Be prepared to discuss on the whiteboard. Temp Students may assume a linear
relationship or not have a clue of any
relationship
t 2) You will fill four beakers with 50, 100, 150 and 200 ml. of water. You will use a heat plate to increase the temperature of the water. Assume that your results from the discussion in Question 1 are the results for 100 ml. of water. Using the graph below, draw a prediction of how you would expect each of the beakers to change temperature when heated on the hot plate at the high setting. Clearly label each of the four volumes. Temp t 3) Now run the experiment in LoggerPro, setting the data collection for ~25 minutes, collecting 12 samples per minute. Run the experiment to plot the temperature versus time until the water in each of the beakers is ~100 degrees Celsius. Sketch your results below, clearly labeling each of the samples. 50 ml
Temp 100 ml
150 ml
200 ml
t 3) Did your measured values match your prediction in Question 2? Please explain why or why not? Answers will vary. They may not know that
increased mass causes a longer heating time
and results in a shallower slope.
4) In a sentence or two explain what effect the amount of water has on the rate at which the temperature changes? More water requires a longer heating time and
shallower temperature/time slope
5) What, if anything, was similar among all of the graphs. What does this indicate? They all have the same plateau, boiling point.
Part II: Down Among the Sheltering Palms (beach) 1) Fill three beakers with equal amounts of water, sand, and ethanol. Use an electronic balance so that you have equivalent masses (somewhere around 100-­‐150 grams). Predict how the temperature versus time graph will look for each of the materials. Clearly label your samples. Temp t 2) Now run the experiment in LoggerPro, setting the data collection for ~25 minutes, collecting 12 samples per minute. Turn the hot plate to high. Do not let the temperature of any of the samples exceed 130 degrees Celsius. If one of the samples reaches that temperature pull the probe out and continue measuring the temperature for the remaining samples. Sketch your results below, clearly labeling each of the samples. Temp Sand heats up past 130. Make sure students
remove. Heats up fastest
Water boils at 95-100 C
Ethanol. Boils at 78-79.
t 3) Did your measured values match your prediction in Question 1? Please explain why or why not? Answers will vary
4) Each hot plate was set at the same level and input the same amount of energy. Assuming each hot plate input the same energy, how does the temperature versus time graph vary based upon the material? Explain. Different materials have different heat
capacities. Sand is about 20 times smaller than
water and ethanol is about half of water.
5) What, if anything, was similar among all of the graphs. What does this indicate? They all reached
a plateau. Sand stopped due
to probe limitations. Water boiled at 100 C while
ethanol was closer
to 78.
Part III: Sweet Georgia Brown 1) Fill a beaker with a combination of ethanol and water. Carefully record the ratio of the two solutions. The combined amount should be around 100-­‐150 ml. Using your results from Part II, predict what a temperature versus time graph would look like. Include your results from the previous section of ethanol and water for comparison. Clearly label all three curves. Water
Temp Mixture should be between
Ethanol
t 2) Now run the experiment in LoggerPro, setting the data collection for ~25 minutes, collecting 12 samples per minute. Turn the hot plate to high. Do not let the temperature of any of the samples exceed 130 degrees Celsius. If one of the samples reaches that temperature pull the probe out and continue measuring the temperature for the remaining samples. Sketch your results below. Temp Results will vary. The boiling point will increase
with a greater water concentration. Don't have
the discuss the slight rise after the plateau. It is
t a more complex reaction
due to solution and
boiling point. They should just see the
increased boiling point and shallower curve.
3) Did your results match your prediction? Be prepared to discuss your results with your classmates on the whiteboard. Be sure to share with your classmates what ratio ethanol and water you used. Part IV: Sweet (Salty) Blues 1) Add 100 ml of water to each of two 250 ml beakers. To one of the beakers add between 2 and 20 grams of salt. Using your results from Part I & Part III, predict what a temperature versus time graph would look like as each liquid is heated. Clearly label each sample on the graph. Water and salt
Temp Water
t 2) Now run the experiment in LoggerPro, setting the data collection for ~25 minutes, collecting 12 samples per minute. Turn the hot plate to high. Do not let the temperature of any of the samples exceed 130 degrees Celsius. Make sure you record the highest temperature. Sketch your results below, clearly labeling each of the samples. Temp t 3) Did your results match your prediction? Be prepared to discuss your results with your classmates on the whiteboard. By adding the salt the boiling point increased. The
heating curve is dependent on mass. The heat curve
for the water and solution is the same. The dissolving
of salt is a physical change. The heat curve is solely
dependent on water, the heat input of the hot plate and
the amount of water.
4) If you were to add salt to your pot to cook dinner, what, if anything, would change? How would this affect the cooking? Be prepared to discus this question and the previous one on the whiteboard at the same time. Increases the boiling point. If the temperature is
higher there is more energy in the water and it
cooks the food faster.