1. Year 8 Chemistry

2. Table of Contents Atoms, Elements and the Periodic Table
Metals, Non-metals and Metalloids
Compounds
Chemical Reactions
Reaction Rates
Acids and Bases
pH Scale
Indicators

3. Atoms and Elements All matter is made up of atoms.
An element is a substance that is made of only one type of atom.
Each element has a letter symbol – usually derived from its English name (first letter in capitals) or its original language name.

4. Periodic Table
The original Periodic Table was constructed by Dmitri Ivanivich Mendeelev, using data collected by many experimental scientists (Physicists and Chemists).
It organises the elements into groups based on their properties – in columns and rows.

5. Sub-atomic Structure
Each atom is made of three types of particles – electrons, protons and neutrons.
The atomic number of an element tells us how many protons an atom has.
The mass number of an element tells us how many protons plus neutrons an atom has.
Each atom has an equal number of negative (electrons) and positive (protons) charges – which means the atom has an overall neutral charge.
charge
position
mass
Electrons
Negative
Shells of energy
Nil
Protons
Positive
Nucleus
1 amu
Neutrons
Neutral

6. Metals, Non-metals & Metalloids
The three main groups of elements are:
Metals – they are usually solid at room temperature, often shiny, can be shaped (malleable), drawn into wires (ductile) and usually conduct heat and electricity.

7. Metals, Non-metals & Metalloids
Non-metals – they are usually gases at room temperature, they are semi-conductors of electricity or heat, are brittle and therefore can’t be drawn into wires or shaped

8. Metals, Non-metals & Metalloids
Metalloids – these are a small group of nine elements that have a mixture of characteristics from both the metal and non-metal groups, including Astatine – an element so rare that there is less than a third of a gram in the earth’s surface.

9. Compounds
Compounds are formed when elements join together as the result of chemical reactions.
They have a set formula and different properties to the elements that make them. For example; Hydrogen and Oxygen gases combine to form water (2H2 + O2  2H2O)

10. Chemical Reactions
Substances that react together are called reactants.
The substances they produce are called products.
Not all elements are able to react with other elements.

11. Chemical Reactions
Physical Changes – no new substance is produced, but some of the properties may change.
Chemical Changes – occur following a chemical reaction and the properties of the products do change.

12. Chemical Reactions How do we know a reaction has occurred?
Production of Gas
Production of Light or Heat
Change of Mass
Permanent Change in colour
Formation of a precipitate.

13. Law of Constant Mass
Antoine Laurent Lavoisier developed the law of constant mass in the 1750’s – not long before losing his head to the guillotine
“Matter is neither created nor destroyed, rather it is simply transferred or transformed.”

14. Reaction Rate The speed a reaction takes place at is effected by:
Temperature
Concentration of reactants
Size of particles of reactants
Use of a catalyst

15. Acids and Bases
Acids are a group of chemicals with similar properties, one is that they are sour to taste.
Acids occur naturally and are found in foods and our digestive systems.
However, they can cause problems in the environment when in too great a concentration or in the wrong place.

16. Acids and Bases
Bases – are a group of chemical compounds that can be thought of as the opposite to acids. They have a bitter taste and soapy feel.
They too are found in nature, but cause problems when too concentrated or in the wrong place.

17. Acid + Base  Salt + Water
Acids and Bases
Neutralisation – when acids and bases combine in a chemical reaction they cancel each other out and form a salt and water.
Acid + Base  Salt + Water

18. pH Scale
The degree of acidity or ‘basisity’ are measured on the pH scale.
Acids are found between 1 and 7 and Bases between 7 and 14 on the pH scale with 7 being seen as neutral

19. Indicators We use a range of indicators to measure pH Litmus Paper
Universal Indicator
pH probes