Measuring Density

1. Density

Density is the amount of mass per unit volume of a substance.

Formula

Density = Mass ÷ Volumeρ = m / V

Units of Density

• g/cm³

• kg/m³

2. Mass

What is Mass?

• Mass is the amount of matter in an object

• It does not change with place

Measuring Mass

• Measured using a balance or weighing scale

• Types:

  • Electronic balance

  • Beam balance

Units of Mass

• gram (g)

• kilogram (kg)

3. Volume

What is Volume?

• Volume is the amount of space occupied by an object

A) Measuring Volume of Regular Solids

Use a ruler and calculate:

• Cube / cuboid: Volume = length × width × height

• Cylinder: Volume = π × r² × h

Units: cm³ or m³

B) Measuring Volume of Irregular Solids

Use water displacement method:

Steps:

1. Fill a measuring cylinder with water

2. Note the initial water level

3. Put the object into the water

4. Note the final water level

5. Volume = final level − initial level

C) Measuring Volume of Liquids

• Use a measuring cylinder, beaker, or pipette

• Read the liquid level at eye level

Units:

• milliliter (mL)

• liter (L)

4. Measuring Density

Density is calculated, not measured directly.

Steps:

1. Measure the mass of the object

2. Measure the volume of the object

3. Use the formula:

Density = mass ÷ volume

Example

Mass = 300 g Volume = 100 cm³

Density = 300 ÷ 100 = 3 g/cm³

5. How Mass is Measured

• Tool: balance or scale

• Unit: g or kg

• Tells how heavy an object is

6. How Volume is Measured

• Regular objects: ruler + formula

• Irregular objects: water displacement

• Liquids: measuring cylinder

• Units: cm³, m³, mL, L

7. Why Density is Important

• Identifies materials

• Explains floating and sinking

• Used in science, engineering, and research