chemistry revision notes

    Cards (23)

    • acids are solutions that reacts with alkalis, turns litmus paper red and has a pH of lees than 7
    • alkalis are solutions that contain excess OH- ions, turns litmus paper blue and has a pH of more than 7
    • neutral is a solution that is neither acidic or alkaline and has a pH of 7
    • 0-6 acidic
    • 7 neutral
    • 8-14 alkaline
    • yellow/orange/red - acid -the closer to red the stronger the acid
    • green - neutral
    • blue/purple - alkali - the closer to purple the stronger the alkali
    • blue litmus paper turns red under acidic conditions
    • red litmus paper turns blue under alkaline conditions
    • independent variable - changed
    • dependent variable - observed and measured
    • controlled variable - kept the same
    • chemical change - new substances formed and they are not easily reversed
      signs of chemical change - colour change, temperature change, gas produced, light produced, odour produced, precipitate formed
    • physical change - no new substances formed and is easily reversed, often involves a change of state
    • endothermic reactions take in energy from the surroundings
      some rections are exothermic because - breaking bonds requires energy, making bonds release energy, more energy is taken in than given out
    • exothermic reaction transfers energy to surroundings
      some reactions are exothermic because - breaking bonds requires energy, making bonds releases energy, more energy is given out than taken in
    • for a reaction to occur, particles of the reactants must collide with eachother
    • rates of reaction will increase if there are more high-energy collisions between particles
    • heat energy - unit is J joules
    • temperature - units is °C
    • 7 stores of energy - thermal, kinetic, chemical potential, gravitational potential, elastic potential
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