The screw we used weighed 31 grams (1.1 ounces) in air. When submerged in water it weighed 27 g. In corn syrup the weight was 25 g. These are the red numbers in the chart below. We used this data, along with the knowledge that water has a density of 1 g/cc, to calculate the volume and density of the screw, and the density of corn syrup. The numbers we calculated are in blue.

Our calculations

The screw weighed 4 g less when submerged in water than when weighed in air. According to the law of buoyancy, this means that the screw displaced, or pushed aside, 4 g of water. Since 4 g of water occupies 4 cc of space, the volume of the screw must also be 4 cc.

Since the screw weighs 31 g its density is 31 g / 4 cc = 7.75 g/cc. Our textbook says that the density of steel is 7.8 g/cc so this is pretty close.

The screw weighed 25 g when submerged in corn syrup. The screw displaced 6 g of syrup. The volume of corn syrup displaced by the screw has to be 4 cc since the volume of the screw is unchanged. 4 cc of corn syrup weighs 6 g so the density of corn syrup is 6 g / 4 cc = 1.5 g/cc. Our textbook claims that the density of corn syrup is 1.38g/cc. Our result is a bit high. Maybe our corn syrup is different or maybe there is some inaccuracy in our spring scale.

		Digging Deeper
		Find out more about
	buoyancy.

Try these ideas

1. Repeat this experiment with other liquids such as corn oil or glycerine.
2. Use an object made of a different metal such as aluminum or lead.
3. Mercury is an unusual metal in that it is liquid at room temperature. Its density is 13.5 g/cc. What would happen if we put the screw we used for this experiment into a container filled with mercury?