- Matter is anything that occupies space and has mass.
- Element is a pure substance, which can neither be decomposed nor built from simpler substances by any physical or chemical means. It contains only one kind of atom.
- Broadly speaking, elements can be divided into metals, non-metals and metalloids.
- A compound can be decomposed into two or more simpler substances. In its formation, energy is usually evolved or absorbed.
- The components of a mixture can be separated by simple mechanical means.
- The smallest particle of an element or a compound, which can exist in the free state, is called a molecule.
- According to Dalton's atomic theory, all matter is made up very small particles called atoms, which cannot be further divided.
- The law of constant proportions states that all pure specimens of a compound always contain the same elements combined together in the same proportion by weight.
- A mole contains 6.023 x 1023 particles. This is called Avagadro's number.
