Combining Elements D. Crowley, 2007

Combining Elements To know what happens when elements combine, and to be able to name compounds To know what happens when elements combine, and to be able to name compounds

Element or not? Name of substance Formula Single element? More than one element? Oxygen O2O2O2O2 Carbon monoxide CO HeliumHe Water H2OH2OH2OH2O Sodium chloride NaCl Carbon dioxide CO 2 YES YES YES YES X X X X X X YES YES

New materials Remember, a compound is formed when two or more elements are chemically bound This results in the compound having different properties than the original elements had E.g. oxygen and hydrogen are a gases, yet combine this together in a chemical reaction and they will form water, a liquid at room temperature E.g. sodium (a grey metal) and chlorine (a greenish-yellow gas) are both very dangerous. But burn sodium in chlorine, and you produce sodium chloride - (table salt)

Naming rules To make your chemical name, you simply combine the names of the elements you reacted together to make your compounds E.g. carbon + oxygen  sodium + chlorine  iron + oxygen  copper + oxygen  carbon dioxide sodium chloride iron oxide (rust) copper oxide The ide is added to the end to tell us the elements have joined together, forming a compound When you add oxygen and 2 other elements, the name usually ends in ate

Symbols A chemical formula is made up of the symbols for the elements it contains E.g. carbon monoxide is CO This tells us it contains carbon and oxygen - for every one carbon atom there is one oxygen atom Many chemical formulas also contain numbers - these tell you what the ratio of elements in the compound is E.g. carbon dioxide is CO 2 This means that for every carbon atom there is, there are two oxygen atoms

Practice Ide Using your sheet, see if you can predict what compound will be made. Be careful of the name If you complete this, try and work out the symbol equation. Ate If you have completed this, try table 2 You have five minutes…

Element + Element  Compound Element+  Compound Carbon (C) +Oxygen (O)  Carbon (C) +Oxygen (O 2 )  Hydrogen (H 2 ) +Oxygen (O)  +  Hydrochloric Acid (HCl) Magnesium (Mg) +Oxygen  +  Iron Oxide (Fe 2 O 3 ) Carbon monoxide (CO) Carbon dioxide (CO 2 ) Water (H 2 O) Magnesium Oxide (MgO) Hydrogen (H) Iron (II) (Fe) Chlorine (Cl)

Element + Element + Oxygen  Compound Element+ +Oxygen  Compound ++  Calcium carbonate (CaCO) Calcium carbonate (CaCO 3 ) Copper+Carbon+Oxygen  Copper Carbonate (CuCO 3 ) Calcium (Ca) Carbon (C) Oxygen (O)

Copper Parcels Experiment: - You are going to hammer squares of copper into a tight parcel that is as air tight as possible You are then going to heat this over a Bunsen burner (using the tongs) Once you have done this, let the copper cool down and tidy up your desk Write down what you have found - explain the difference in colour Represent this using a word and symbol equation

Differences Hopefully you found that you copper parcel has shown a good colour change - one area which was heated has changed to a black, sooty colour, whilst the other remains the original copper colour. This is because some of the copper (the area which was heated) has reacted with the oxygen, forming the compound copper oxide which is a darker red colour (different properties to the original copper element) *The black formation is carbon from the Bunsen copper + oxygen  copper oxide 2Cu + O 2  2CuO