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SMC|Academic Programs|Physical Sciences|Heat and Water

Heat and Water

When you mix water of different temperatures, the final temperature of the the mixture is between the two initial temperatures. In this lab we will investigate what things you need to know to predict exactly what temperature the mixture will have.

Part 1

You need three Styrofoam cups and 2  large metal containers (one to boil water in and one to keep cold water in), and a thermometer. Fill one of the cups about 1/3 full (a little less). Mark with a pen on the side of the cup the water level. Pour that water into the second cup, and mark it. Fill the first cup to its mark again, and then pour that into the second cup so it now has twice the original amount of water - mark that water level too. So these two cups have marks that we can call "1X" and "2X" amounts of water. The third cup needs no marks.

You could use regular thermometers or computer connected ones to measure the temperature - we'll use the ones connected to the computer, since they're more fun! Turn on the ULI interface, connect a "Direct connect temperature probe" in the first DIN slot and then start "LoggerPro". Under "File" click on "Open.." then "Experiments", "Probes and Sensors",  "Temperature Probes", and then "Direct Connect Temperature Probe" to start the program that enables you to measure temperature using these probes.

While waiting for the water to heat up, look through the rest of this lab and think about the predictions it asks you to make. You will also be able to play with the thermometer! Please DON'T place the plastic tip of the thermometer directly on the hotplate - it could melt.

When the water is hot enough (around 90 degrees or hotter), fill one cup to its 1X mark with hot water and fill a second cup with the same 1X amount of cold water.

 temperature of cold water = 
 temperature of hot water = 

Predict what temperature the mixture of the two waters will be.

 PREDICTED temperature of mixture = 

Now mix the two waters and measure the temperature.

 MEASURED temperature of mixture = 

 

 If  there was a difference between your prediction and measurement what might have caused it?

 

 

Now, throw out the mixture of water.

Part 2

Fill 1 cup to its 2X mark with HOT water and fill the other cup with COLD water to its 1X mark.

 temperature of cold water = 
 temperature of hot water = 

Predict what temperature the mixture of all the water will be.

 PREDICTED temperature of mixture = 

Now mix the two waters and measure the temperature.

 MEASURED temperature of mixture = 

 

 If  there was a difference between your prediction and measurement what might have caused it?

 

 

 

 Which water sample changed its temperature most? Why do you think this happened?

 

 

Now, throw out the mixture of water.

Part 3

Fill 1 cup to its 2X mark with COLD water and fill the other cup with HOT water to its 1X mark.

 temperature of cold water = 
 temperature of hot water = 

Predict what temperature the mixture of all the water will be.

 PREDICTED temperature of mixture = 

Now mix the two waters and measure the temperature.

 MEASURED temperature of mixture = 

 

 If  there was a difference between your prediction and measurement what might have caused it?

 

 

 

 Which water sample changed its temperature most? Why do you think this happened?

 

So, what things determine the final equilibrium temperature of  mixtures of water?

 

Now, throw out the mixture of water.