C3

• Atom


  The smallest part of an element that can exist
• Mass


  The amount of matter an object contains. Measured in kilograms (kg) or grams (g)
• Element


  A substance made of one type of atom only
• Molecule


  A collection of two or more atoms held together by chemical bonds
• Formula


  A combination of symbols that indicates the chemical composition of a substance
• Relative formula mass (Mr)


  The sum of the relative atomic masses of the atoms in the numbers shown in the formula
• Ionic compound


  An ionic compound occurs when a negative ion (an atom that has gained an electron) joins with a positive ion (an atom that has lost an electron)
• Law of conservation of mass


  No atoms are lost or made in a chemical reaction. Instead, the atoms join together in different ways to form products.
• In a balanced symbol equation, the number of atoms of each element is the same on both sides of the equation.
• The total mass of the products is equal to the total mass of the reactants.
• The sum of the relative formula masses of the reactants is equal to the sum of the relative formula masses of the products.
• Calculations using the law of conservation of mass

  Mass of one substance in a reaction can be calculated if the masses of the other substances are known
• Closed system


  In chemistry, a system in which no substances can enter or leave during a reaction
• Reactions in closed systems, such as a stoppered flask, have the total mass of the beaker and the substances in it stay the same during the reaction.
• Solution


  Mixture formed by a solute and a solvent
• Non-enclosed system


  In chemistry, a system in which gases or other substances can enter or leave during a reaction
• Solute


  The dissolved substance in a solution
• In non-enclosed systems, the total mass will look as if it has decreased if a gas escapes, or increased if a gas is gained. However, the total mass stays the same if the mass of the gas is included.
• Dissolve


  When a substance breaks up and mixes completely with a solvent to produce a solution
• Thermal decomposition


  Type of reaction in which a compound breaks down to form two or more substances when it is heated
• Solvent


  The liquid in which the solute dissolves to form a solution
• Concentration


  A measure of the mass or amount of solute dissolved in a given volume of solvent or solution
• Calculating concentration


  Mass of dissolved solute in g / Volume of solution in dm^3
• Concentration can be increased by dissolving more solute in a given volume of solution or by allowing some of the solvent to evaporate