Glossary
The terms of this app, from A to Z, each with the page that explains it.
- Boiling point
The temperature at which a liquid becomes gaseous. For a pure substance it is always the same.
- Change of state
In a change of state such as melting or evaporating the substance stays the same. Only the state of matter changes.
- Chemical reaction
In a chemical reaction substances turn into other substances. The new substances have different properties from the old ones.
- Coefficient
A coefficient is the big number in front of a formula. It tells how often the formula occurs.
- Compound
A compound consists of atoms of different elements joined in a fixed ratio, for example water or carbon dioxide.
- Conservation of mass
In a chemical reaction the total mass of the substances afterwards is just as large as before.
- Formula
A formula uses element symbols to show which atoms a substance is made of. A small subscript number, the index, tells how many atoms there are.
- Melting point
The temperature at which a solid becomes liquid. For a pure substance it is always the same.
- Molecule
A molecule is a small particle made of several joined atoms, for example a water molecule.
- Particle model
In the particle model every substance consists of very small particles, which you imagine as balls.
- Property of a substance
A property of a substance is something you can use to recognise a substance and to tell it from other substances, for example its colour, its smell, its hardness or its density.
Explained on the page Properties of substances – a short recap
- Reaction equation
A reaction equation describes a reaction with formulas. The starting substances are on the left of the arrow, the products on the right.