Chemical Reactions: Fast and Slow Investigating how temperature affects the rate of a reaction
A glow stick contains two chemicals in separate tubes. When you crack a glow stick the inner glass tube (which is made of very thin glass) breaks. This allows the two substances in the glow stick to react.
Using glow sticks, plan, design, carry out and write up an investigation about how temperature affects the rate of a reaction.
1. What energy transfers are happening in the glow stick?
2. How can you tell whether the chemical reaction is happening faster or slower in each glow stick?
3. Some people place glow sticks in the freezer to make them last longer. Why do you think this works?
Rate of reaction
Niamh was investigating the reaction between magnesium and hydrochloric acid, which produces magnesium chloride and hydrogen gas. The data that she collected can be seen in the table below.
Investigation
Time needed to collect 10 cm3 of the hydrogen gas (s)
A 15
B 4
C 46
Use the information in the table to answer the following questions: 1. Which investigation had the slowest rate? 2. Which investigation had the fastest rate? 3. In which investigation is it likely that the testing conditions were the same?
4. The only variable that Niamh changed was the temperature. Which investigation took place at the highest temperature?
Concentration and Rate of Reaction
As you increase the concentration of reactants, you increase the number of particles in a given volume.
As there are more particles in concentrated solutions, there are more collisions. These collisions increase the rate of the reaction.
z Fig. 12.4.3
The effect of concentration on reaction rate
211
Low concentration results in fewer collisions
High concentration results in more collisions
D 15 E 30 z c a Glow worms glow F
because of a chemical reaction that takes place in their tails. This is called bioluminescence. Glow worms glow brighter at warmer temperatures.
