Density

Outcomes

Know that as the density of matter increases, the number of particles in the matter increases.
Know that as the density of particles decreases, the number of particles in the matter decreases.

What is density?

Density is a measurement that compares the amount of matter an object has to its volume.
An object with a lot of matter in a certain amount of volume has high density.
An object with a little matter in the same amount of volume has a low density.
Temperature has an effect on density. When the temperature of a substance increases, density decreases because the atoms are moving all around the place having less matter in one space. When the temperature of a substance decreases, the density increases because the atoms move slower making the atoms stay in one place. Many substances follow this rule, but there are exceptions. Water is one such exception. When water freezes, it makes ice that is less dense than liquid water.

Calculating density

Activities:

1. Define mass?

2. Define volume?

3. Define density and show the formula for calculating density.

4. Why does changing the shape of an object have no effect on the density of that object?

5. Aluminum is used to make airplanes. Cast iron is used to make weightlifting equipment. Explain why the densities of these metals make them useful for these purposes?

6. What is the density of water? Remember for water 1g=1ml=1cm3

7. Why does an air bubble rise to the surface of a glass of water?

8. Calculate the densities of the following objects. Remember to place units after each number.

Object A length = 6cm width = 3cm height = 1cm mass = 36g

volume = _____ density = _____

Object B length = 10cm width = 5cm height = 2cm mass = 300g

volume = _____ density = _____

Object C Use the water displacement method to determine the density of object C (silly putty). initial water level in graduated cylinder = 25ml final water level after placing silly putty into graduated cylinder = 29ml mass of silly putty=8g

volume = _____ density = _____

9. Which of the following materials will float on water (density 1 g/ml)?

air = .001 g/cm3 corn oil = .93 g/cm3 glycerine = 1.26 g/cm3 corn syrup = 1.38 g/cm3 wood = .85 g/cm3 steel = 7.81 g/cm3 rubber = 1.34 g/cm3 ice = .92 g/cm3 water = 1.00 g/cm3

10. Assuming the materials don’t mix, show how the materials would "stack up" in a graduated cylinder.

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