EDEXCEL GCSE FOUNDATION MATHS - What is Density

Edexcel GCSE Foundation Maths: What is Density?

What is Density?

Density is a measure of how much mass is contained in a given volume. It tells us how tightly packed the matter is in an object.

Formula:

The formula for density is:

Density = Mass / Volume

Units:

• Mass: Usually measured in grams (g) or kilograms (kg).
• Volume: Usually measured in cubic centimeters (cm³) or cubic meters (m³).
• Density: Usually measured in grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

Example:

Imagine you have two cubes, both the same size. One cube is made of wood, and the other is made of lead. The lead cube will be much heavier than the wooden cube, even though they have the same volume. This is because lead has a higher density than wood.

How to Calculate Density:

1. Measure the mass of the object. Use a balance scale to find the mass in grams or kilograms.
2. Measure the volume of the object.
   • For regular shapes like cubes or rectangular blocks, you can calculate the volume using the formula: Volume = Length × Width × Height.
   • For irregular shapes, you can use water displacement method:
     • Fill a graduated cylinder with water and record the initial volume.
     • Carefully place the object in the cylinder, ensuring it is fully submerged.
     • Record the new volume.
     • Subtract the initial volume from the new volume to find the object's volume.
3. Divide the mass by the volume. This will give you the density of the object.

Example Calculation:

• Mass of an object: 50 grams
• Volume of the object: 20 cm³

Density = Mass / Volume
Density = 50 g / 20 cm³
Density = 2.5 g/cm³ 

Key Points to Remember:

• Density is a property of matter. It doesn't change with the size or shape of the object.
• Objects with higher densities are more compact, meaning they have more mass packed into a given space.
• Density can be used to identify different materials.

Applications of Density:

• Identifying materials: Density can be used to determine the type of metal or other material an object is made of.
• Engineering and construction: Engineers use density to calculate the weight and strength of building materials.
• Science: Density is an important concept in many areas of science, including physics, chemistry, and biology.

Practice Problems:

1. A block of wood has a mass of 100 grams and a volume of 50 cm³. What is its density?
2. A piece of metal has a density of 8 g/cm³. If its volume is 2 cm³, what is its mass?

Answers:

1. Density = 2 g/cm³
2. Mass = 16 grams