Atoms and Molecules

Elements and Compounds

Substances and Mixtures

Atoms

➲ The simplest particles that make up matter

➲ Represented by balls

Molecules

➲ Molecules are made when two atoms are attracted to each other with strong forces and bond

➲ When two or more atoms join together to make a molecule, it is called a chemical reaction

Elements

➲ Elements are substances formed by atoms of a single type

Elements cannot be broken down into more simple substances

➲ There are three kinds of elements: Atomic elements Molecular elements Elements with a crystal structure

Compounds

➲ Compounds are substances formed by different atoms, always combined in fixed proportions

They are represented by formulas formed by the symbols of their elements and subscript numbers which indicate the number of atoms of that element in the compound

CO2

➲ Two types of compounds Molecular compounds Compounds with a crystal structure

1)Pure substances

Formed by similar particles

➲ Homogeneous mixture/solution: when we cannot differentiate between their components

Sea water, air

➲ Heterogeneous mixture: when we can distinguish the components of the mixture

Granite rock

2)Mixtures

Substances and Mixtures

➲ Pure substances are formed by similar particles (atoms or molecules)

Most of the matter that we see is a mixture of substances

➲ The main difference between pure substances and mixtures is that the first have well definied specific propertires: density, fusion and boiling temperatures, while mixtures do not