Locusts and Glowsticks

Public summary: 

What do glowsticks and locusts have in common? Watch what happens as we heat them up and cool them down - how long can you get your glowstick to glow? How fast can you make the locusts move?

Using glow sticks to talk about chemical kinetics.
Useful information
Kit List: 

- lamp (heat only if possible)
- 2 tanks of locusts
- glow sticks
- knife/ scissors to open glowstick packet
- ice cubes for cooling
- washing up bowl

Packing Away: 

Bin any used glow sticks.
Return unused glow sticks to stores.

Frequency of use: 

Use cooling glow sticks in ice to stop the light-emitting reaction to show that reactions happen faster when they're warm.

Locusts (cold blooded) in warm and cool environments can be used to point out that this is true of the reactions of life too, but this is not essential.

Possible activities:
- Demonstrating how cooling slows down reactions using glowsticks and ice.
- Demonstrating how cooling slows down reactions using locusts and ice.

Other things to talk about:
- Other reactions which are affected by heat which we see in our everyday lives.

Tips for demonstrating:

- It is quite useful to be aware for this experiment how much difference the "Really Cool Show"/liquid nitrogen demonstration makes to how quickly children pick up the ideas you feed them, especially about temperature/ reactions and the fact that solid carbon dioxide takes up much less space than the gas.


- Place tanks of locusts side by side, shine the lamp on the outer face of one of the tanks.

- Break and cool a couple of glowsticks in icy water as "ones I prepared earlier".

- Start with glowsticks- get a glowstick out. Remove end-cap and ribbon as they cause confusion (children think they're important).

- Have the children seen glowsticks before? When? Fireworks night? Parties?. If not, it may be best to snap the glowstick first and see what it does.

- Do they know how glowsticks work? The usual answer, if any, is "You bend them".Explain that what happens when you bend them is that the inner glass tube breaks and the two chemicals mix. (With the yellow glowsticks you can see the glass tube before breaking it

- Get one of the children to snap the glowstick and give it a shake now that it's glowing.

- How can we stop it? Suggestions usually include "bend it again", "unmix it", "open the tube". Deal with these ideas first - unmixing could be compared to mixing red and green paint to make brown then trying to unmix. Quite often a parent will prompt the child to say "put it in the freezer" in which case the next bit is explaining why, not drawing out what!

- A possible route to how to stop a reaction is through how we stop food from going off... work children round to "put it in the fridge".

- Explain that everything is made up of little bits moving around and banging into each other, and if things are hotter the little bits move faster and bang into each other harder.

- Describe reactions as bits banging into each other and knocking bits off/ getting new bits stuck on, possibly pointing out that you hurt yourself more if you fall off your bike/ fall over when running than if you trip up when walking.

- Get the icy water out and explain that it is colder than room temperature, more like your fridge at home. Put the glowsticks in the water and put it away again.

- Move on to locusts and ask the children to look at the locusts, and to decide which set are moving about more. In general they're pretty obliging and it will in fact be the "warm tank" locusts which move about more.

- Explain to children that the locusts, like them, get their energy to move about from reactions of their food. Tell them that their (the children's) bodies have lots of systems to make sure they stay at the same temperature... they are warm-blooded (many will have heard the term before).

- Explain that locusts haven't got these systems (they are cold-blooded) so they can only get energy out of their food to move about if they're warm enough. Point out that this is like the glowsticks, which only give off light if they're warm enough.

- This all tends to be very counter intuitive to the less scientific parent, some have trouble with the idea that locusts don't just want to lie down if it's hot, like they do themselves!

- Get the icy water out again and show that the glowsticks are glowing much less. They probably won't have gone out yet (unless the group were particularly fascinated by the locusts!).

- How can we start the glowstick glowing again/much brighter?. Warm up the glowstick by removing it from the water (carefully, it will be very cold!) and holding it.

- Explain that now the particles can bang into each other again as they have enough energy (are moving around fast enough).

- If children are still engaged, can talk about the magnetic molecular models.

- Give the glowstick to one of the children. Repeat 'til fade.


- Other reactions which are affected by heat which we see in our everyday lives.

- The differences between hot-blooded and cold-blooded animals.

At one point this experiment was done using dry ice. If doing so in the future this needs to be separately risk assessed - currently we have no source of dry ice.
- If using dry ice: be aware that a box of dry ice with a glowstick inside it will have a fascinating (at least to a small child) glow. It is very important to retain control of the experiment (I often achieve this by sitting on the lid of the polystyrene dry ice box) whilst giving your demonstration since if a small sibling loses interest in your talk (s)he may try to conduct an experiment of her/his own!
- If using dry ice, can talk about dry ice and what it is, maybe put a couple of pieces in a bowl of water and watch them bubble, talk about the gas expanding and taking up more space.
If Dry ice is used for packing away purposes, it can be left in well ventilated area to boil.

Risk Assessment
Date risk assesment last checked: 
Wed, 15/01/2020
Risk assesment checked by: 
Date risk assesment double checked: 
Wed, 15/01/2020
Risk assesment double-checked by: 
Polly Hooton
Risk Assessment: 

Look at glow stick in darkened box then cool using ice/salt mix. Look at it again. Compare with activity of locusts in hot and cold conditions. Wooden "molecules" can be stuck and unstuck from each other (using magnets) to show the idea of a chemical reaction.

Hazard Risk Affected Person(s) Likelihood Severity Overall Mitigation Likelihood Severity Overall
Glow stick contents Glow stick contents are non-toxic, but contents is potentially damaging to eyes. Glass ampoule inside the glowstick is broken to activate stick, but small chance of contents leaking. All 2 3 6 Take care not to break outer skin of glowstick. Demonstrator must know the location of the nearest eyewash. If giving glowsticks to children to take away, warn the parents/guardians that contents should not be allowed to come into contact with eyes and that glowsticks should not be put in the mouth or chewed. Ideally do not give glowsticks to children below the age of about eight years.
If glowstick contents come in contact with skin, rinse immediately. If they get into an eye, demonstrator must call a first aider and may perform an eye wash if trained and confident to do so.
2 2 4
Salt and ice mix Salt ice mix is cold. Contact with it can hurt and prolonged contact could cause skin damage. All 3 3 9 Do not allow anyone else to touch the ice water.
If cold solution is spilt onto anyone rinse off with copious cold (but not freezing cold) water. Call a first aider in the case of injury.
2 3 6
Salt mix Salt solution is strongly ionic and therefore electrically conducting. Risk of electric shock in contact with lamp. All 2 3 6 Ensure that all electrical appliances and plugs are above ground level and safe from spills of salt solution. Do not allow children to put their hands in the cold solution. Do not allow anyone else to touch the lamp, dry hands if you need to touch it.
Call first aider in the case of an injury/shock. Turn off electric power at mains.
Read attached electrical RA.
1 3 3
Salt solution High ionic strength solution will hurt on contact with eyes. All 3 2 6 Advise children not to touch their eyes, if they have touched the wet glow sticks, as the salt will sting.
If an accident occurs, call a first aider, who will consider giving an eyewash.
2 2 4
Lamp The lamp warming the locusts can get hot - risk of burns. All 3 3 9 Warn children not to touch lamp. Do not leave lamp on for unnecessarily long periods of time.
Call a first aider in case of injury. Bathe affected area under cold water for at least 10 minutes if you suspect a burn.
2 2 4
Rare earth magnets Reaction model contains rare earth magnets which are very strong - risk of them slamming together and smashing, or trapping skin. All 3 2 6 Demonstrator to check at beginning of experiment that the magnets are firmly in place in the wooden "molecules". Do not use if magnets are not firmly in place.
Call first aider in case of injury.
1 2 2
Locusts Repeated exposure to locusts could cause the demonstrator or the public to either have an asthma attack (if they already have asthma) or for them to develop an allergy to locusts. All 1 4 4 Demonstrator should be aware of any breathing changes, rash, runny nose that occurs to them when they are near the locusts, and should not perform experiment if they get these symptoms. Demonstrator should also be aware of the possibility that others may be allergic/get an asthma attack.
Do not demonstrate if you find yourself to be allergic to locusts. Call a first aider in the event of an asthma attack. Calm person down, sit them down. Get person to use inhaler if they have one.
1 3 3
This experiment contains mains electrical parts, see separate risk assessment.
This experiment is sometimes run in a darkroom, see separate risk assessment.
Publicity photo: