Science exam

• All substances are composed of atoms
• Elements are made from only one type of atom
• There are about 100 different elements
• An atom is the smallest part of an element that can exist
• Elements have specific physical and chemical properties
• Physical properties= state, appearance, smell, magnetic. Etc
• Chemical properties= what it reacts with and how reactive it is
• Elements are organised in the periodic table
• The periodic table is organised into periods and groups
• Groups are vertical columns
• Periods are horizontal rows
• Elements in a group have similar chemical properties
• Metals are on the left hand side of the staircase and non-metals are on the right hand side of the staircase
• Compounds are formed from elements by chemical reactions
• Chemical reactions always involve the production of one or more new substances
• A compound contains two or more elements chemically joined together in fixed proportions
• A compound has different properties from the elements its composed
• Compounds can only be separated into elements by chemical reactions
• A molecule is two or more non-metal atoms chemically joined together - this can be an element like H2 or a compound H2O
• Usually the metal goes first and the non-metal goes second
• The chemical formulae of a molecule or compound tells you which elements and how many atoms of each are in one molecule
• Speed = distance / time
• Distance travelled = speed x time
• a solution with ph 7 is neutral
• Aqueous solutions of acids have pH values less than 7
• Aqueous solutions of alkalis have pH values greater than 7
• An aqueous solution is any solution in which the solvent is water