Name: ______
Density of Water Experiment
1. Why does the water always seem colder at the bottom of a lake? Is it because the sun only shines on the top or is there another reason? Explain.
2. Why are icebergs so dangerous for ships at sea and what's unique about the way water changes from liquid to solid?
Here's what you'll need:
Three 250 mL beakers filled to 100 mL of room temperature water
A 250 mL beaker of cold water filled to 100 mL
A 250 mL beaker of hot water filled to 100 mL
Red and blue food coloring
If you dropped a few ice cubes into a glass of room temperature water---- What would the ice cubes do? If you said they float, congratulations. You've just proven that ice is less dense than liquid water! Ice is "cool" stuff because most substances actually get denser when they change from a liquid to a solid, but not water.
As water freezes into ice, the volume actually increases.
Okay, so if water gets less dense when it freezes, then what happens when different-temperature waters meet?
Here's the challenge:
3. How do different-temperature waters react when they flow together? Do they sink, float, or mix together? Write down your prediction and explain why you think it is correct.
What you do:
4. Begin by predicting what will happen when ice-cold water meets room-temperature water. Make sure you explain why you think this might happen.
5. Then predict what will happen when hot water meets room temperature water. Make sure you explain why you think this might happen.
6. After you've made your predictions, put 2 drops of blue food coloring into the cold-water beaker and stir it. Slowly pour 50 mL of the blue water into a beaker of room temperature water. What does it do? Was your prediction right?
7. Now, put 2 drops of red food coloring into the hot water beaker and stir it. Slowly pour 50 mL of the red water into another beaker of room temperature water. Did it do the same as the cold? Based on your experiments, what do you think happens to the density of water as it changes temperature?
8. Based on the observation that ice floats on (and is less dense than) water, make a reasoned prediction about how waters of different temperatures will react when they flow together.
9. Pour the remaining 50 mL of blue-colored cold water and the remaining 50 mL of red-colored hot water into the last beaker of room temperature water. Do waters of different temperatures sink, float, or mix together? Explain what happened.
Understand that when water gets hot, it gets less dense; and that when water gets cold, it gets denser EXCEPT when it freezes and turns to ice, in which case it becomes less dense!