# Describe and Explain the Conservation of Mass

In this worksheet, students will recall what is meant by the conservation of mass, and apply it to situations such as changes of state and dissolving.

Key stage:  KS 3

Curriculum topic:   Physics: Matter

Curriculum subtopic:   Particle Model

Difficulty level:

#### Worksheet Overview

What is mass?

Mass tells us how much matter is contained inside a substance. It is not the same as weight, which is a force measured in Newtons and depends on the strength of gravity.

Mass on its own has nothing to do with gravity -  it is not a force, and it is measured in kilograms (or grams).

The only thing that an object's mass depends on is how many particles are contained inside it.

Conservation of mass

Mass is always conserved. This means that in any chemical reaction or any physical process, the total mass at the start will equal the total mass at the end.

For example, if 100 grams of ice is melted, it will turn into 100 grams of water. This is a change of state and is a physical reaction.

Even in a chemical reaction, where a total 100 grams of different substances were mixed together, it would still make a total of 100 grams of new substances.

Ultimately, you cannot create or destroy mass because you cannot create or destroy particles.

Let's have a go at some questions now. If you need to check back to this page, just click on the red help button on the screen at any point.

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