| Question | Answer |
| Column 1 | alkali metals |
| Column 2 | alkaline- earth metals |
| Column 3-12 | transition elements |
| Column 13 | metalloids |
| Column 17 | halogens |
| Column 18 | noble gases |
| H20 | 2 hydrogen atoms and 1 oxygen |
| C6H1206 | 6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms |
| Mg(OH)2 | 1 magnesium atom, 2 oxygen atoms and 2 hydrogen atoms. |
| Element | Is a substance made up of only 1 type of atom.
E.g. Sulfur |
| Compound | Is a substance made up of 2 or more DIFFERENT types of atoms chemically joined together.
E.g. H20 |
| Mixture | Consists of 2 or more different substances mixed together but NOT chemically combined.
E.g. Air |
| Non-metals | Most are gases
Don't conduct electricity & not ductile
Often have atoms joined together to form molecules e.g. H2, O2. |
| Metals | Most found in earth's crust
Mostly shiny, good conductors.
Most are solids at room temp. |
| Alloys | A mixture of 2 elements 1 of which is a metal.
Often harder than metals.
Sometimes used to prevent rusting.
Have different properties (melt and boil point) |
| Physical change | Easily reversible
Change of state, temp, shape
Don't involve formation of new chemical
. Dissolving is an example of a physical change |
| Chemical change | Isn't easily reversed
Occurs when substance combine in different ways to form new substance |
| Signs of Chemical reaction | Gas given off
Change in temp
Smell given off
Light given off
Colour change
New substance made |
| Combustion | You need 3 things:
oxygen, fuel and heat |
| Burning | Hydrogen + oxygen = water |
| Metals reaction | Metals react with oxygen to form oxides |
| Rusting | Chemical name- Hydrated iron oxide.
For rust to occur you need water and oxygen
. rusting is a chemical reaction |
| Prevention of rusting- Paint | Adv. cheap
Dis. friction causes it to flake |
| Prevention of rusting- Oil | Adv. cheap
Dis. not long lasting |
| Prevention of rusting- Galvanising | Adv. long lasting, effective
Dis. very expensive
coat iron w/ thin layer of zinc. This reacts with oxygen instead of iron so iron doesn't rust. |
| Prevention of rusting- Alloying | involves mixing iron w/ other chemical such as Carbon.
dis. very expensive |
| Reversing Chemical Changes | Difficult to reverse but can be done. ELECTORLYSIS is a common way of causing a compound to break down into constituent elements.
E.g. water splits into hydrogen gas and oxygen gas. |
| Carbon dioxide | to make- add marble chips to hydrochloric acid.
to test- bubble the limewater- if limewater goes from clear to cloudy then gas is carbon dioxide |
| Hydrogen gas | to make- add metal- magnesium to hydrochloric acid
to test- take a lit flame to the gas, if it ignites w/ squeaky pop then gas is hydrogen. |
| Oxygen gas | to make- add magnesium dioxide powder to hydrogen peroxide
to test- take a glowing splint to the gas. If the glowing splint relights then the gas is oxygen. |
