Question

topic 8: density
study guide

• formula: density = mass + volume.
• units: g/cm³ or g/ml.
• float/sink: < 1 g/ml = floats; > 1 g/ml = sinks.
• characteristic property: unique for each substance.

activities

1. formula practice: density = ____ + ____
2. multiple choice: mass = 20 g, volume = 4 cm³ → density?

a) 80 g/cm³ b) 5 g/cm³ c) 0.2 g/cm³ d) 24 g/cm³
answer: ____________

1. fill - in - the - blank: if an object floats in water, its density must be ______ than 1 g/cm³.
2. short answer: why is density a characteristic property?
3. problem solving: mass = 36 g, density = 3 g/cm³ → volume =?
4. true/false: two objects with same volume always have same density. ______

Explanation:

Step1: Recall density formula

Density = Mass $\div$ Volume

Step2: Solve multiple - choice question

Given Mass = 20 g and Volume = 4 $cm^{3}$, Density = $\frac{20}{4}=5$ g/$cm^{3}$. So the answer is b).

Step3: Fill - in - the - blank

If an object floats in water, its density must be less than 1 g/$cm^{3}$.

Step4: Answer short - answer question

Density is a characteristic property because it is unique for each substance and does not depend on the amount of the substance.

Step5: Solve problem - solving question

From Density = Mass $\div$ Volume, we can get Volume = Mass $\div$ Density. Given Mass = 36 g and Density = 3 g/$cm^{3}$, Volume = $\frac{36}{3}=12$ $cm^{3}$.

Step6: Answer true/false question

False. Density depends on both mass and volume. Two objects with the same volume can have different masses and thus different densities.

Answer:

1. Mass; Volume
2. b) 5 g/$cm^{3}$
3. less
4. It is unique for each substance and does not depend on amount.
5. 12 $cm^{3}$
6. False