MYP Physics Density Notes

Density Describes How Much Mass Is Packed Into a Volume

1. When you compare two objects of the same size, one might feel much heavier than the other.
2. This is not only about how big the object is, but it is also about what it is made of.

Comparing Size and Mass

1. Objects can be compared by their size (volume) and mass, but this does not fully describe the material.
2. Two objects can:
   1. have the same size but different masses,
   2. have the same mass but different sizes.
3. These differences are caused by how tightly matter is packed inside the object.

What is Density?

1. Density describes how much mass is contained in a given volume.
2. It explains why materials with the same size can have different masses.
   1. High-density materials have particles packed closely together.
   2. Low-density materials have particles spaced further apart or contain air gaps.

$$\text{density} = \frac{\text{mass}}{\text{volume}}$$

Units of Density

1. Standard SI unit of density: kilograms per cubic metre (kg m⁻³).
2. Other commonly used units: grams per cubic centimetre (g cm⁻³).
3. Volume units are cubic, not linear.

Measuring Mass

1. Mass is measured using a balance.
2. Common units are grams (g) and kilograms (kg).
3. Mass must be measured carefully before calculating density.