CHAPTER 21 – RATES OF REACTIONS Factors affecting the rate of reaction
There are a number of factors that affect the rate of a chemical reaction: • temperature • concentration of the reactants • surface area of the reactants • adding a catalyst
Temperature
As temperature increases, the rate of reaction speeds up. For example, bread will bake faster at a higher temperature.
Particles have more energy at higher temperatures. As heat is added to a reaction, the particles that make up the reactants gain more kinetic energy and move faster. When these particles collide, they are more likely to have enough energy to react with each other (activation energy).
: Fig. 21.4 Reaction at 25 °C Reaction at 35 °C Eureka
Glow-worms light up because of a chemical reaction that takes place in their tails. This is called bioluminescence. Glow-worms glow brighter at warmer temperatures.
Effective collision
: Fig. 21.5 The rate of the reactions that take place during baking increase according to temperature
? TEST TUBE
3. a. Plot the following data on a graph, with temperature on the y-axis and time on the x-axis: Time (s)
Volume of hydrogen produced at 20 °C (cm3
8 )
Volume of hydrogen produced at 30 °C (cm3
00 0 30 60 90
120 150 180
16 24 32 40 40
10 20 30 40 40 40
b. What effect does an increase in temperature have on the rate of a reaction? )
: Fig. 21.6 The effect of temperature on the rate of reaction