Rate of Heating

Project #1517 on iSENSEProject.org

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Students explore rate of heating.  Students predict which will come to a boil more quickly, hot or cold water, as well as explain why they believe their prediction is correct.  Students predict how much longer they believe it will take for the other choice to come to a boil.  Students should see that although one boils more quickly than the other, the difference in time is not as great as predicted.   Students then discuss why they think this is so.

 

Data Collection Procedure: 

1. Tap water was used for this experiment.
2. Three (3) cups of tap water were placed in the refrigerator overnight.
3. Chrome book was set up with Vernier program readied for data collection.
4. Hot tap water was run for 2 minutes to get it to hottest point from the tap.  Three cups were measured out and placed in a one quart sauce pan.  Three cups was used to so that as much water as possible would cover the sensor probe.
5. Pot was put on the burner, but burner was not turned on.  A gas stove was used.
6. Data collection started to determine ambient air temperature. 
7. Probe was inserted into pot and when temperature started to level off, burner was turned on high. 
8. Temperature was recorded until water boiled (for several seconds) and temperature leveled off at the boiling point.
9. Contents were emptied and pot was allowed to cool to room temperature, as was the burner.
10. Experiment was repeated using cold water, Steps 6 though 8.

 

Guiding Question:  Which will come to a boil more quickly, hot or cold water? 

 

Student Questions:

1. Which will come to a boil more quickly, hot or cold water?  Why did you select your answer?  

2. How much longer will the other take to come to boil?  Why did you predict what you did?

3.  Draw a graph of how you think the temperature will change until boiling occurs.

4. After looking at the data: 

a. What do you notice about how the temperature changes between the hot and the cold water?

b. Do the lines cross?  Why or why not? 

c. What does the configuration of the lines mean about how fast the temperature is changing in each situation?

Visualization:  After a certain point, the rate of heating is relatively the same for hot or cold water.  Initially, the cold increases at a slightly faster rate than the hot, but that eventually, the rate is pretty much the same.  The hot/cold lines are almost parallel.

Students will usually predict that hot water will come to a boil in less time than cold water.  However, they believe the hot water graph will be much steeper than the cold water graph.

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Name	Units	Type of Data
Time	Seconds	Number
Temperature	Celsius	Number

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Time	Temperature