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CHEMISTRY - TOPIC 4 - Coggle Diagram
CHEMISTRY - TOPIC 4
INCREASING REACTION RATES
Increase Temperature:
high temperature = more energy = more and faster movement = more collisions per second
numbers of successful collisions increases because more collisions have energy above activation energy
EXPIREMENT: investigate the effect of temperature on the rate of reaction between sodium thiosulphate (Na2S2O3) and dilute hydrochloric acid
INDEPENDENT VARIABLE: starting temperature
DEPENDENT VARIABLE: time taken for cross to disappear (s)
CONTROL VARIABLES: concentration and volume of sodium thiosulphate and dilute hydrochloric acid
Catalysts:
catalysts work by providing an alternative reaction pathway with the lower activation energy
catalysts is not a reactant - doesn't react away
Example: enzymes - biological catalyst - protein molecules that speed up chemical reactions - in living cells - respiration + photosynthesis
EXPIREMENT
Decrease volume
reduces space for particle movement - more compact
increasing frequency of collisions
in gases = increase pressure
EXPIREMENT:
Increase surface area
Any reaction involving a solid can only take place at the surface of solid
ADD PHOTO FOR EXAMPLE FROM SCIENCE VIDEO
If solid if split into several pieces = increased surface area = more room for collisions
smaller pieces = larger surface area
EXPERIMENT: investigate the effect of the surface area of calcium carbonate chips on the rate of reaction between calcium carbonate (CaCO3) and dilute hydrochloric acid.
INDEPENDENT VARIABLE: surface area of cubes
DEPENDENT VARIABLE: the time taken for the Co2 to be lost from the open conical flask
CONTROL VARIABLES: mass of calcium carbonate chips
Increase Concentration
more particles in the same amount of space
more particles = more collisions per second
EXPIREMENT:
COLLISION THEORY
DEFINITION: for a chemical reaction to occur the particle involved must collide with each other
Successful Collisions must have:
particles must have enough energy (combined)
minimum amount need is called ACTIVATION ENERGY
particles must have the correct orientation (position/ angle)
RATE OF REACTION
DEFINITION: the rate at which a reactant is used up, or the rate at which a product is formed.
RoR = amount of reactant used up or product formed / time taken