Investigating Water Density Dr. Sanders
Which is denser: cold or hot water? Fresh or salty water? Your objective is to determine what factors affect water density and how differences in density may affect the movement of a fluid like water or air.
EQUIPMENT AND SUPPLIES
- Two clear plastic wide-mouth bottles of the same size and shape. Gatorade and Snapple bottles work well, as do large plastic spice bottles.
- Two colors of food coloring. Blue and red work best. Blue and yellow also work well.
- An index card covered with plastic mailing tape. This “laminates” the card to make it slippery and water repellant.
- Tray (to contain spills).
- Water samples of different characteristics.
- Test Salty water vs. Fresh (tap) water.Temperature of the two samples must be the same, so take your samples from the buckets of room temperature water (on the cart).
- Test Cold water vs. Hot water. The hot water must be very hot! Let the hot water tap run until it gets as hot as possible.For the cold water, use the bucket with ice cubes in it. Don’t put ice in your bottle, though—just liquid water.
- Fill one of the plastic bottles with one type of water, and the other with the other type. Fill the two bottles all the way to the very tip-top!
- Add blue food coloring to one container, and eitherredor yellowto the other. Record which is which (for example, which one is Salty and which one is Fresh).
- Place the laminated index card over the mouth of one bottle. (Make sure the bottle is filled to the very tip-top!)
- Holding the card in place to prevent spills, invert the bottle and place it on top of the other one. Reminder: Both bottles should be completely full!
- Carefully slide the card out, keeping the bottles in place.
- Observe and record what happens to the water.
- Repeat the experiment, but this time switch the positions of the two water samples, placing the opposite sample on top.