cDensity Practice Problems

The density of a substance is a measure of how much mass is packed into a certain volume of the substance. Substances with a high density, like steel, have molecules that are packed together tightly. Substances with a low density, like cork, have fewer molecules packed into the same amount of space.
	The density of a substance can be found by dividing its mass by its volume. As long as a substance is homogeneous, the size or shape of the sample doesn’t matter. The density will always be the same. This means that a steel paper clip has the same density as a steel girder used to build a bridge.

Density = Mass ÷ Volume                 D =  m / v

Use the density formula to solve the following problems. Show all work and the answer must have the correct units. Remember that volume can have different forms. A block of ice with a volume of 3 cm3 would be 3 mL of liquid after being melted.


1. What is the density of CO gas if 0.196 g occupies a volume of 100 ml?

Answer: 0.196g/100ml = 0.00196g/ml

2. A block of wood 3 cm on each side has a mass of 27 g. What is the density of the block? (Hint, don’t forget to find the volume of the wood.)

Answer:  27g/ 3cm = 9g/cm

3. An irregularly shaped stone was lowered into a graduated cylinder holding a volume of water equal to 2 ml. The height of the water rose to 7 ml. If the mass of the stone was 25 g, what was its density?
(Volume = the amount of displaced water)

Answer: 25g/5ml = 5g/ml

4. A 10.0 cm3 sample of copper has a mass of 89.6 g. What is the density of copper?

Answer: 89.6/10 - 8.69g/cm3

5. Silver has a density of 10.5 grams/cm3 and gold has a density of
19.3 g/cm3. Which would have the greater mass, 5cm3 of silver or 5cm3 of gold?

Answer: Gold would have the greater mass.

6. Five mL of ethanol has a mass of 3.9 g, and 5.0 mL of benzene has a mass of 44 g. Which liquid is denser?

Answer: Benzene is denser.

7. A sample of iron has the same dimensions of 2 cm x 3 cm x 2 cm. If the mass of this rectangular-shaped object is 94 g, what is the density of iron?

Answer:  The density is 8 if rounded.


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8.  Why does a heavy piece of wood float in water?

Answer: The density of the wood allows it to float.  It is a lighter object , therefore it will begin to float and stay that weigh with less pressure added to it.


9.  Why does a heavy metal ship float in water?

Answer: It floats because the mass and density it contains.

10. How can you find the volume of an object with an irregular shape by placing it in water?

Answer: When you place the object in the water , the water gets higher by however many. The number it goes up by is your volume.