|#8: Density Explorations|
Make a rainbow with different densities of sugar water.
Using six heat-safe containers, add 1 tablespoon of sugar to the first cup and add an increasing amount of sugar to each cup, adding an additional tablespoon each time.
Add food coloring to each cup, according to the colors of the rainbow.
Move from least dense to most dense, releasing each new layer on the bottom of a test tube, with the straw, instead of trying to pour it onto the top.
Density Column That Holds Objects
Add three liquids to a glass: corn syrup, water and oil and they will layer naturally by density. Then add a rock, a grape, an ice cube and a cork are. The rock lays on the bottom, the grape sits on top of the corn syrup, the ice cube sits on top of the water and the cork sits on top of the oil.
Density Layers in Soil
Archimedes' Density Discovery
The most widely known anecdote about Archimedes tells of how he invented a method for determining the volume of an object with an irregular shape. A new crown had been made for King Hiero II, and Archimedes was asked to determine whether it was of solid gold, or whether silver had been added by a dishonest goldsmith. Archimedes had to solve the problem without damaging the crown, so he could not melt it down into a regularly shaped body in order to calculate its density. While taking a bath, he noticed that the level of the water in the tub rose as he got in, and realized that this effect could be used to determine the volume of the crown. The submerged crown would displace an amount of water equal to its own volume. By dividing the weight of the crown by the volume of water displaced, the density of the crown could be obtained. This density would be lower than that of gold if cheaper and less dense metals had been added. Archimedes then took to the streets naked, so excited by his discovery that he had forgotten to dress, crying "Eureka!" meaning in Greek "I have found it!"With this story in mind, we set up a simple demonstration to show this concept. Don't worry no bathtub involved. We took a bowl and set it in a baking dish. We then filled the bowl to the brim with water.
We then took two objects of identical weight.We determined that the rubber ball symbolized the lump of gold, and placed it in the bowl of water. It displaced a certain amount of water.We then placed our candle, which represented the crown, and we saw that it displaced some more water, showing that although its weight was similar, its density was not.
I have found out that both 4 quarters and 5 Hershey's Chocolate Kisses weigh 1 ounce, so these can be used. You can use a postal scale if you have one, to prove this as part of your experiment. Carry out the experiment the same as above and you should see that the candies have more mass and displace more water.
Salinity and Temperature Densities
|Sometimes you will see little currents in the straw as one type/color of liquid passes another.|
This is a bit more challenging. The task is to create four distinct layers in straw cylinders using only colored water and salt. The ocean is made up of layers of water of different densities. Cold water is denser than warm water, water with salt is denser than fresh water. The more closely packed the molecules in a substance, the denser the substance.
|Please excuse the messiness of our school table.|
I usually clean it off after every activity, but has been one of those crazy weeks for us.
For this experiment you will need: - 4 Styrofoam cups or insulated containers, kosher salt, plastic straws, medium raw potato, medicine droppers, a package of food coloring
Have students write in their journals a key to the colors:
red-hot and salty
blue-cold and salty
yellow-hot and fresh
green-cold and fresh
Have four containers to hold water and label them as above, adding about 15 drops of the appropriate food coloring to each container. Fill the containers with water, two with hot water and two with cold. Add 1/3 cup of kosher salt to both the red and blue water. Stir. Add ice to the blue and green containers.