Descent into the Ice
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Student Handout
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Is It Icy Water or Watery Ice?
You
are familiar with ice and water coexisting—ice on a pond or ice cubes in
your drink. But where is the point at which water turns into ice, or ice into
water? In this activity you will study the borderline between water and ice.
Procedure
Choose one person in your team to run the experiment, one to be the
timekeeper, and one to be the recorder.
Fill one beaker with ice water and one beaker with room-temperature water.
Put ice in the 16-ounce foam cup.
Make an ice/salt bath in your 8-ounce foam cup. Put 2 tablespoons of ice
water in the cup, add a teaspoon of salt, and stir well with your plastic
spoon. Add ice in halfway up the cup and stir well again.
Add 3 centimeters of room-temperature water to your test tube. Place the
thermometer in the water for 1 minute and then record the temperature in the
data table on your "Experiment Data Sheet" handout. Hold the test tube at the
top as you do this so that your hand does not increase the temperature of the
water.
Place the test tube all the way into the foam cup, and have the timekeeper
start timing when you do so. Don't let any ice get in the test tube.
Record the temperature every 15 seconds. Once each minute, the student
running the experiment should quickly pull out the test tube to see if any ice
has formed, and the recorder should note the tester's observations.
At the end of every 3 minutes, the recorder should add more ice to make up
for any ice that has melted. Ice can be added all the way to the top of the
cup.
Continue the experiment for 12 minutes.
When you finish, put the test tube in warm water to melt the ice and free
the thermometer.
Using your graph paper, graph your results with time on the x-axis
and temperature on the y-axis.
Questions
Write your answers on a separate sheet of paper.
What was the temperature of the flat section in your graph?
How long did the temperature stay the same? Why do you think it remained the
same?
Why do you think the temperature began to fall again at the end of the flat
section?
What can you conclude about the temperature when you had a liquid-only
state? A solid-only state? What about when both states coexisted?
How would the shape of the graph change if you started with more water in
the test tube? Explain your reasoning.
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