C1

• test for hydrogen: lit splint in hydrogen, squeaky pop test
• test for oxygen: glowing splint in gas - relights splint
• test for carbon dioxide: gas collected and bubbles in lime water - turns cloudy
• atmosphere contains - 78% nitrogen, 21% oxygen, 0.04% carbon dioxide
• Earth was formed 4.6 billion years ago, an atmosphere composed of Carbon dioxide and lava
• test for chlorine: litmus paper in chlorine turns red then white
• conservation of atoms - no atoms are created or destroyed they just rearrange to form new substances
• exothermic reaction - release more energy to surroundings than they absorb
• endothermic reaction - more energy is absorbed than released
• Reactants - Atoms in reactants are held together by chemical bonds, energy needs to be absorbed from surroundings to break the bonds (endothermic)
• products - when atoms rearrange they form new bonds making new products, energy is released to the surroundings when new bonds are formed (exothermic)
• Hydrogen fuel cells cars do not use fossil fuels, instead they use hydrogen, to get hydrogen electrolysis is used which uses an electrical current to split water into hydrogen and oxygen. the hydrogen is collected and used
• Potable water - drinking water that is safe to drink and is free from harmful microorganisms
• Chlorination - chlorine is added to the water to kill bacteria
• Catalytic converter - A device that is found in car exhausts to reduce harmful nitrogen oxide emissions
• Sulphur dioxide (SO²) - produced in combustion of fossil fuels, causes acid rain
• Carbon monoxide (CO) - produced in incomplete combustion poisonous to humans
• Nitrogen oxide (N₂O) - produced in car engines, greenhouse gases
• Complete combustion - oxidation reaction occurs when a substance chemically combines with oxygen e.g carbon + oxygen = carbon dioxide
• Incomplete combustion - occurs when there is a lack of oxygen present
• Bond breaking - requires energy to be absorbed from surroundings
• Bond forming - releases energy to surroundings
• Activation energy - minimum energy needed to break bonds so that a reaction can begin