glow stick kinetics experiment

• what's a rough guide for how an increase in temp affects rate of reaction?

  for every 10 degree celsius rise in temp, the rate of reaction will double.
• why does temp increase rate of reaction?

  as temp rises the molecules move faster and so collide more often and so the number of reactions per second increases.
• what does this experiment demonstrate?

  that heating a reaction increases its rate as the molecules involved move faster and so collide more frequently. And that cooling a reaction has the opposite affect so molecules will move slower, colliding less frequently and the number of collisions will be less.
• what equipment do we need for this experiment?

  glowsticks, a transparent pudding bowl, ice and hot tap water.
• what is method 1?

  1. fill the pudding bowl with ice cubes and add some water and salt.
  2. break and shake a glow stick, then place it in the pudding bowl so the lower half is immersed in the ice slush bath and the upper half isn't.
  3. after a few minutes, you should notice a difference in the brightness of the lower half compared to the upper half.
• in method 1, why do we add salt to the pudding bowl?

  adding salt reduces the temperature of the resulting slush.
• in method 1, explain the reasons behind the result.

  after a few minutes you should be able to notice a difference in the brightness of the lower half compared to the upper half. This is due to the rate of reaction in the lower half being lower than the upper half as the molecules of hydrogen peroxide and oxalate ester are moving slower and so colliding less than the molecules in the upper half.
• what is method 2?

  1. take 2 identical glowsticks, break and shake them both and place 1 in the freezer and the other in a bowl of hot water.
  2. leave for 5-10 minutes than take both out and compare their brightness, the one from the freezer will be significantly dimmer than the one from the hot water.
  3. now place the glowstick from the freezer in the hot water for 1 minute then take it out and shake it and repeat. The brightness of the glowstick should increase as it gets hotter since the molecules are colliding more frequently.
• in method 2, explain the results.

  the brightness of the glowsticks is directly proportional to the temperate, reactions get faster as they get hotter and slower as they get colder. This is why freezing food allows it to be kept longer as the reactions within the bacteria which normally would cause it to spoil are slowed down by the lower temperature.