Rate Of Reaction & Temperature
Noadswood Science, 2012
Wednesday, April 19, 2023
To understand how temperature affects the rate of reaction
Reaction
How do we know if a reaction has taken place? Color change Gas given off Precipitate forms Temperature change pH change
Rate Of Reaction
A variety of factors affect the rate of reaction, including: -
Temperature
Concentration of a dissolved reactant
Pressure of a reacting gas
Surface area of reactants
Catalysts
Particles
How do the particles differ in cold water and boiling water?
In boiling water the particles collide more often and with more force – they are moving quicker and with more energy…
Collision Theory
Particles need to collide with enough energy (activation energy) to react
This activation energy is needed to break the bonds in the reactants – reactions only occur it the particles have enough initial ‘activation energy’
Collisions
Chemical reactions occur when particles of reactant collide with enough energy to react
Anything that increases the chance of effective collision increases the rate of reaction (e.g. surface area, temperature, pressure, using a catalyst etc…)
Collisions
If the temperature is increased: The reactant particles move more quickly More particles have the activation energy or greater The particles collide more often, and more of the
collisions result in a reaction The rate of reaction increases
Equation
The rate of reaction can be worked out simply, recording either the amount of reactant used / product formed and the time taken…
Rate of reaction = amount of reactant used or amount of product formed
time taken
Experiment
Plan and carry out an experiment investigating how temperature affects the rate of reaction (record your results)…
Measure 50cm3 sodium thiosulfate into a conical flask
Heat the sodium thiosulfate to the required temperature
Add 5cm3 hydrochloric acid and begin timing whilst swirling the flask (stop the clock when the cross disappears)
Repeat using different temperatures
Graph your results and write a conclusion
Experiment
Temperature (oC)
Time for cross to disappear (sec)
Test 1 Test 2 Test 3 Average
30oC
40oC
50oC
Experiment
Why did the cross fade quickest with the highest temperature?
Why did the cross fade?
Was this a fair experiment?
Experiment
sodium thiosulphate + hydrochloric acid → sodium chloride + sulphur dioxide + sulphur + water
2HCl + Na2S2O3 → 2NaCl + SO2 + S + H2O
The cross faded quickest when the temperature was greatest as a temperature increases will increase the rate of reaction – this is because the particles are moving quicker and with more energy, increasing both the chance the particles collide and the force at which they do
The cross fades as a sulfur forms (this is solid and causes the solution to go cloudy), although it is difficult to swirl with the same amount of force, so this would make our experiment unreliable!
Collisions
At higher temperatures molecules move faster – as a result there are more collisions per second and so a faster reaction occurs
Question
Question
Question