ELEMENTS AND COMPOUNDS

Science 9

Models of Matter

The Particle Theory of Matter All matter is made up of tiny particles All particles of one substance are the same.

Different substances are made of different particles

The particles are always moving – the more energy they have, the faster they move

There are attractive forces between the particles – the closer they are, the more attracted they are to one another

Pure Substances

Contains only one kind of particle

Ex. Aluminum, gold, copper, oxygen

Ex. Carbon dioxide, sugar, table salt

Mixtures

Contains at least two different substances

Ex. Pop, bread, ice cream

Classifying Mixtures - Homogeneous

A solution can be made up from solids, liquids or gases

Ex. Air is a solution of gases

Ex. Salt water Alloys are

mixtures of metals

Classifying Mixtures – Heterogeneous

Heterogeneous mixtures have different visible parts

Ex. Pizza, cereal and milk, yogurt and berries

Pure Substances - Elements Elements cannot be chemically broken

down into smaller parts They are organized on the periodic table Most are found in nature but an

increasing amount are being made synthetically

Ex. Hydrogen, helium, lithium, etc.

Pure Substances - Compounds Elements can chemically combine to

form compounds Compounds are composed of two or

more elements in a fixed proportion They can be written in chemical formula Ex. Water is two parts hydrogen, one

part oxygen H2O CO2

C6H12O6

What is all matter made up of? Atoms are the basic building blocks of all

matter

Every element on the periodic table is composed of one type of atom

The periodic table is composed of over 100 elements, so this means there are over 100 kinds of atoms

Atoms Make Molecules

When atoms join other atoms, they form molecules

They must contain at least two atoms but the amount of combinations are limitless

Sometimes, the atoms are all the same in a molecule, like O2, and sometimes they are different, like NaCl

Models of Molecules

It is impossible for us to physically see molecules because they are so small

We construct models of them, instead, to help visualize what they look like