YEAR 9 CHEMISTRY REVISION GOOD LUCK!

Structure of Atom In the cloud : Electrons (negative) In the Nucleus: Protons (positive) Neutrons (neutral)

Subatomic Particles In an atom: The Protons = the Electrons If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral The neutrons have no charge; therefore they do not have to equal the number of protons or electrons

Atomic Number Atomic number: this number indicates the number of protons (and electrons) in an atom Ex: Hydrogen’s atomic number is 1 So hydrogen has 1 proton and 1 electron Ex: Carbon’s atomic number is 6 So carbon has 6 protons and 6 electrons

Physical Change A changes in certain properties such as: Shape State (Solid, liquid, gas) NO NEW SUBSTANCES ARE CREATED Examples: dissolving sugar, melting ice

Chemical Change Chemical changes produce new substances Heat Gas Bubbles Light Examples: making toast, burning wood

Metals React with acids They are more of them than non-metals and are on the left side Conducts electricity Glows quickly and cools quickly Generally sink Shiny and strong They a sonorous (make a ringing sound) Solids at room temperature They Malleable and Ductile

Non Metals On the right side of the periodic table Generally float Gases at room temperature Don't conduct electricity and so they are insulators Really slow to heat up or cool down Very brittle- which means they break easily Very dull looking

Acids pH 1-6 React with Metals turn blue litmus paper red corrosive sour taste red/pink in universal indicator Common examples: Milk, HCL, Citric Acid

Bases pH 8-9 Turns red litmus paper blue bitter blue/ purple in universal indicator common examples: soap, detergent, cleaning products

Neutrals pH 7 No reaction to litmus paper Green in universal indicator ACID + BASE = Neutralisation Common Examples: Water

Acid and Metal Reactions Acid + Metal -> Salt + Hydrogen Gas Acid + Metal Carbonate -> Salt + water + Carbon Dioxide Acid + Base -> Salt + Water