C1

• In solids, strong attractive forces hold the particles in place, so that they can only vibrate in position. 

  As the substance is heated, the particles gain energy and vibrate faster and faster. Eventually, the particles have so much energy that they can overcome the forces holding them together, and the substance melts into a liquid.
• The particles in a liquid slide past one another as the liquid flows. The particles in liquids are held close to each other by weaker attractions than those between solid particles. This means that there is more space between the particles in a liquid than in a solid. As a result, liquids take up the shape of any container they are put into. They also have no fixed volume - if you heat a liquid it expands and takes up more room.
• Solids have a rigid structure because the particles are packed tightly together and held in place by strong intermolecular bonds
• When a gas is heated, the particles gain kinetic energy and move faster. 

  If the gas is trapped within a container that cannot expand, it means that the volume of the gas is fixed, and so the pressure inside the container increases.
• exothermic reaction

  a reaction that releases heat into the surroundings
• endothermic reaction

  a reaction that absorbs heat from the surroundings
• what type of reaction is shown by this reaction profile?

  endothermic

  
• what type of reaction is shown by this reaction profile?

  exothermic

  
• what happens during a chemical reaction?

  The bonds of the reactant molecules are broken. Then, the atoms rearrange themselves to form the bonds of the product molecules.
• In the first billion years, the gases that formed Earth's early atmosphere came mainly from which source?

  Volcanos
• During the first billion years, which two gases were released from volcanoes?

  Water vapor and carbon dioxide.
• 1. Around a billion years after it formed, the earth began to cool. This allowed water vapor to condense into liquid water and form the oceans. 
  2. When the oceans formed, carbon dioxide dissolved in the water, and carbonates were precipitated, producing sediments.
  3. This dramatically reduced the amount of carbon dioxide and water vapour in the atmosphere
• Starting 2.7 billion years ago, which process started to increase the amount of oxygen in the atmosphere, and further decreased the amount of carbon dioxide?

  Photosynthesis by plants and algae
• Describe why carbon monoxide is harmful for humans. 

  When we breathe in carbon monoxide, it diffuses into our bloodstream and binds to our haemoglobin. This reduces the amount of oxygen it can carry so less oxygen is carried to our tissues. This can result in fainting, coma or death.
• When burning fossil fuels, how is sulfur dioxide formed?

  Sulfur is an impurity in some fossil fuels and is oxidised when they're combusted
• When burning fossil fuels in an engine, how are nitrogen oxides formed?

  Nitrogen from the air is oxidised from the high temperatures within the engine.
• what are the greenhouses gases?

  methane, carbon dioxide, water vapour
• greenhouse effect

  Solar radiation from the sun passes through the atmosphere and hits the earth. Some of this energy is reflected back into space, and some of it is absorbed by the earth then re emitted into space. Some of this energy makes it all the way back into space, however some is absorbed by molecules called greenhouse gases. This trapped energy keeps the atmosphere warmer and more stable than it would be.
• chlorine gas test

  expose it to damp blue litmus paper, if chlorine is present the litmus paper will turn red and then bleach white
• oxygen gas text

  expose it to a glowing splint, if oxygen is present the glowing splint will relight
• hydrogen gas text

  expose it to a lit splint, if hydrogen is present there will be a squeaky pop
• carbon dioxide test

  bubble it through lime water, if carbon dioxide is present the limewater will turn cloudy
• hydro oxygen fuel cell

  the oxygen enters the cathode compartment and hydrogen enters the anode compartment
• main advantages of a hydro oxygen fuel cell

  hydrogen and oxygen are both renewable. fuel cells last longer than batteries. the reaction doesn't produce any pollutants.
• main disadvantages of a hydro oxygen fuel cell

  hydrogen gas requires a large space to store. it requires energy to produce hydrogen. hydrogen is highly flammable.
• what is the criteria for water to be potable?

  levels of dissolved substances must be fairly low. ph level must be between 6.5 and 8.5. no micro organisms.