Science T2

• Chemical equation


  Describes what happens in a chemical reaction
• General structure of a chemical equation

  Reactants - products
• Word equation


  Replacing the reactants and products with chemical name or each substances
• Reactants must equal the number of atoms of even numbers in the products. When this happens, a formula is referred to as being balanced
• Exothermic reaction


  Chemical reactions that release energy in the form of heat or light
• Endothermic reaction


  Chemical reactions that absorb energy
• Combustion


  Any chemical reaction in which a substance burns in oxygen gas to produce light or heat - exothermic reaction
• Hydrocarbon


  Substances with only carbon and hydrogen atoms
• Incomplete combustion


  Combustion in a limited supply of oxygen
• Respiration


  A chemical reaction that goes on inside the cells of all living things
• You exercise


  You get hot because of respiration. When you require more energy, you respire more and so you produce more heat
• Corrosion


  Most metals will combine with oxygen gas in the air to form metal oxides
• Decomposition reaction


  A chemical reaction in which one reactant breaks apart into two or more products
• Combination reaction


  Two reactants combine together to form a single product
• Precipitation reaction


  When two clear solutions are mixed together, they react to form an insoluble solid that precipitates out of the solution
• Neutralization reaction


  Occurs when an acid reacts with a base
• Acid


  Any substance that releases hydrogen ions when dissolved into water
• Neutralization equation


  Acid + base ---> salt + water
• Rate of reaction


  The speed at which a chemical reaction proceeds
• Factors affecting rate of reaction

  • Temperature
  • Concentration of reactants
  • Surface area
  • Agitation
  • Catalyst
• Increasing temperature


  Normally increases the chemical reaction
• Concentration


  The amount of a particular substance present in a particular volume or liquid
• Increasing concentration of reactants

  Increases the rate of reaction
• Agitation


  Stirring reactants
• Catalyst


  Chemicals that speed up chemical reactions but are not consumed or used up in the reaction. They reduce the amount of energy required to convert reactants into products and make it easier for reactant molecules to collide and form products.
• Enzymes


  Biological catalysts. Natural molecules that hold reactant molecules together until they rearrange to form products.
• Law of conservation of mass: during a chemical reaction, atoms cannot be created or destroyed.