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