chapter 11 chemical

• Physical change 

  -No new substances formed 

  -Can be reversed 

  -Easily separated 
• Chemical change 

  -One or more substances formed 

  -Cannot be reversed 

  -Hard to separate 
• before after change

  H2O H2O physical change

  CO2 CO chemical change
• Reactants vs products 

  Reactants

  -Substances that react with each other

  Products

  -new substances formed 

  E.g carbon+oxygen=carbon dioxide and water 

  Carbon and oxygen is reactants 

  Carbon dioxide and water is product 
• Representing chemical reactions 

  Reactants on the left and products on the right 

  E.G methane +oxygen -> carbon dioxide + water 
• Rearrangements of atoms 

  -rearrange themselves and combine chemically to form products 

  -atoms are neither destroyed or created 

  -number of atoms remains the same during the reaction 
• Combustion 

  -substance in the presence of oxygen to form one or more new substances 

  Carbon + oxygen -> carbon dioxide 
• Thermal decomposition 

  -substance breaks down into two or more simpler substances during heating 

  Calcium carbonate -> calcium oxide +carbon dioxide 
• Oxidation 

  -substance gains oxygen 

  -rusting formed when iron reacts with oxygen and water 

  Glucose + oxygen -> carbon dioxide + water 
• Neutralisation 

  -when an acid is mixed with an akali 
• ACIDS 

  -Sour taste 

  -Dangerous as they can burn skin 

  -Blue litmus paper turns red in contact 

  -Reacts with alkalis, metals and carbonates 
• ALKALI 

  -Bitter taste 

  -Soapy feeling 

  -Red litmus paper turns blue

  -React with acids in neutralisation reactions 
• Chemical reactions between acids and alkalis

  Acid + alkali -> salt + water 

  hydrochloric acid + sodium hydroxide -> sodium chloride + water
• Chemical reactions between acids and metal

  Acid + metal -> salt + hydrogen 

  hydrochloric acid + magnesium -> magnesium chloride + hydrogen
• Chemical reactions between acids and carbonation 

  Acid + carbonate -> salt + carbon dioxide + water 

  hydrochloric acid + magnesium carbonate -> magnesium chloride + carbon dioxide + water

  limewater can test for the presence of carbon dioxide by turning cloudy
• Ph scale 

  -ph values below 7 are acidic 

  -lower the ph level, the more acidic the solution 

  -solution neither alkaline nor acidic, its neutral 
• Neutralisation


  • Alkaline added to acid, pH level increases
  • Acid added to alkaline, pH level decreases
• Mixing


  1. Two or more reactants are mixed together to form one or more products

  2. Hard to separate

  3. Chemical change
• Heating


  An increase in temperature

  Heat is needed for thermal decomposition and combustion
• Types of indicators 

  -litmus paper

  -methyl orange

  -bromothymol blue

  -phenol red
• Exposure to light

  -photosynthesis is a chemical reaction that occurs in the presence of light

  Carbon dioxide + water ---> glucose + oxygen
• Interaction with oxygen

  Copper turns green in the presence of water and oxygen

• Electroplating


  1. Electric current passed through a solution containing gold particles

  2. Flows through from one point to another

  3. Coat the objects in gold
• Cooking


  • Softens food
  • Improves flavour
  • Easier for body to absorb nutrients
• Respiration

  1. Glucose molecules react with oxygen

  2. Produce carbon dioxide and water

  3. Energy released allows an organism to survive and reproduce
• Decay

  1. Breaking down organic matter into simpler substances

  2. Nutrients return to the environment

  3. Vacuum packing food slows down decaying

  4. Reduce the amount of oxygen

  5. Limit growth of bacteria
• Rusting


  • Occurs in humid climates
  • Painting
  • Oiling
  • Galvanising
  • Drying are ways to prevent this process
• Carbon monoxide

  -Burning of fuel in the presence of insufficient oxygen

  -Colourless, odourless, highly toxic gas

  -reduce amount of oxygen taken up by red blood cells leading to headache and death
• Sulfur dioxide


  • Burning of sulfur-containing fuel
  • Volcanic eruptions
  • Irritate eyes, nose and lungs
  • Dissolve in rainwater to form acid rain
  • Harm aquatic life and damage buildings
• Oxides of nitrogen

  • Burning of fuel at high temperature
  • Reaction of nitrogen and oxygen in the air
  • irritate eyes, nose and lungs
  • dissolve in rainwater to form acid rain
  • harm aquatic life and damage buildings