4.1 RATES OF REACTION
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What determines if a chemical reaction can happen
If the reactant particles collide with enough energy
What is the the activation energy
The minimum amount of energy the reactant particles need to react
What happens to particles that collide with little energy
They rebound and remain unchanged
What is collision frequency
How often the particles collide with each other
What is the percentage succsess
The percentage of the collisions that have enough energy to react
What are the 5 factors that affect rate of reaction
1) Solid surface area 2) Temperature 3) Concentration 4) Pressure (gas only) 5) Catalysts
Higher surface area increases rate because:
More solid is exposed to other particles - So collision frequency is higher - More successful collisions per unit time
Higher concentration / gas pressure increases rate because:
There is a higher proportion of particles per unit volume - So collision frequency is higher - So the proportion of successful collisions is higher per unit time
Higher temperature increases rate because:
The particles have more kinetic energy - So the percentage of collisions with enough energy is higher - There are more successful collisions per unit time
Catalysts increase rate because:
They provide an alternative route with a lower activation energy - So the percentage of collisions with enough energy is higher - So there are more successful collisions per unit time
How do you increase the surface area of a solid
Cutting or grinding it
What is the independent variable in the calcium carbonate surface area experiment
the surface area of the calcium carbonate chips
What is the dependent variable in the calcium carbonate surface area experiment
Volume of Carbon Dioxide produced
Name 3 control variables in the calcium carbonate temperature experiment
Mass of calcium carbonate chips, volume and concentration of HCl, Temperature
How does the surface area of the calcium carbonate chips in the surface area experiment affect the results shown on a graph measuring CO2 production
Higher surface area chips have a steeper start because the rate has increased so the volume of carbon dioxide is increasing faster, however they all end in the same place because, the amounts of reactants hasn’t changed, so eventually the reaction produces the same amount of CO2.
What is the independent variable in the black cross concentration experiment
The concentration of the sodium thiosulphate
What is the dependent variable in the black cross concentration experiment
Time taken for the cross to disappear
What is the 3 control variables in the black cross concentration experiment
Total volume of solution, concentration of HCl and temperature
How is rate calculated
1 / Time Taken ( in seconds)
What is the unit for rate
S ^ -1
What are the results of the concentration black cross experiment
Proportional - Straight line through the origin
What is the independent variable in the magnesium ribbon temperature experiment
Temperature from Hydrochloric Acid
What is the dependent variable in the magnesium ribbon temperature experiment
Time taken for the magnesium ribbon to disappear
What are the 4 control variables in the magnesium ribbon temperature experiment
Mass and surface area of magnesium, volume and concentration of HCl