Density Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Density.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

The mass of a substance per unit volume, measuring how tightly packed the particles are within a material.

Density answers 'how heavy is this for its size?' A small lead ball is heavier than a large foam ball — lead is denser.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Density is an intensive property — it doesn't change with amount. A drop of water and an ocean have the same density.

Common stuck point: Density is not the same as weight. A large block of wood can weigh more than a small piece of iron, but iron is still denser.

Sense of Study hint: When solving density problems, use the triangle method with the formula d = m/V. First identify which two of the three quantities (density, mass, volume) you know. Then rearrange the formula to solve for the unknown: m = d \times V or V = m/d. Finally, check that your units are consistent — common units are g/cm³ for solids and g/mL for liquids.

Worked Examples

Example 1

easy
A block of aluminum has a mass of 135 g and a volume of 50.0\,\text{cm}^3. Calculate its density.

Solution

  1. 1
    Use the density formula \rho = \frac{m}{V}.
  2. 2
    Substitute the given values: \rho = \frac{135\,\text{g}}{50.0\,\text{cm}^3}.
  3. 3
    Evaluate the quotient to get \rho = 2.70\,\text{g/cm}^3.

Answer

\rho = 2.70\,\text{g/cm}^3
Density is an intensive property — it does not depend on the amount of substance. Every sample of pure aluminum has the same density, making it useful for identification.

Example 2

medium
A piece of metal has a mass of 78.0 g. When placed in a graduated cylinder containing 25.0\,\text{mL} of water, the water level rises to 35.0\,\text{mL}. Calculate the density and identify the metal if possible. (Iron = 7.87\,\text{g/cm}^3, Copper = 8.96\,\text{g/cm}^3, Zinc = 7.13\,\text{g/cm}^3)

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Will an object with density 0.85\,\text{g/cm}^3 float or sink in water (\rho = 1.00\,\text{g/cm}^3)?

Example 2

hard
A solid cube has a side length of 3.0 \text{ cm} and a mass of 81 \text{ g}. Calculate its density. If the cube is cut in half, what is the density of each piece? Explain.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

physical property