Did you get a rain gauge set up yesterday? Remember to check it today so that you can start to collect data.
Today we are going to look at a chemical reaction between an acid and an alkali, both of which you can find in your kitchen: vinegar and baking soda.
Remember: although you are going to be working with everyday food items, it is still possible to injure yourself. Vinegar will sting if it gets into a cut or into your eyes. You are also going to be heating up the vinegar so that it boils – you need to take care not to splash any or let it spit as you can burn yourself. The saucepan will be very hot. Do not put a lid on the saucepan when the liquid is boiling as the pressure will build up.
- Measure 1 litre of clear vinegar and slowly add 3-4 tablespoons of baking soda. Stir until it is dissolved and then put the mixture on the heat to boil. You will see some bubbles when you are dissolving the baking soda. The chemical name for baking soda is sodium bicarbonate, so what gas do you think might be in the bubbles?
- Leave to boil for 30 minutes. You’ll start to notice a white substance on the side of the pan. This is sodium acetate, save a bit of this to use later.
- When you see a crust (sodium acetate anhydrous) begin to form, take the liquid off the heat and transfer it to a container. Cover the container to prevent the substance crystallising, then cool it in an ice bath for 15 minutes, or a fridge for a bit longer.
- The liquid needs to cool below room temperature to become a supercool liquid. Once it has cooled, take the lid off and add some of the white sodium acetate you collected earlier.
- As the sodium acetate is introduced, the liquid will begin to crystallise and after a few seconds the entire liquid will ‘freeze’. However, if you touch it, the substance will feel hot not cold, because the process of crystallisation is exothermic. That means that energy is given out in the form of heat, so the liquid turns into a solid.
this happens because most substances have a freezing point, where the molecules rearrange from a liquid into a solid or crystal arrangement. Sodium acetate trihydrate, or hot ice, is a supercool liquid, which means even though it’s a liquid at room temperature, the molecules will rearrange into solid form when disturbed (by adding sodium acetate).
The chemical reaction that takes place when the baking soda reacts with the vinegar is:
Were you right earlier, did you guess that the gas being made was carbon dioxide?
I hope you enjoy today’s experiment. Don’t forget to send us some pictures of your experiment here at The Left-Handed Lemon blog and you could win a prize!
If you want to have a go at tomorrow’s, you will need plastic cups, split pins and cardboard.
Until next time, keep calm and apply some Science!
This activity has been taken from the downloadable pack found on https://www.britishscienceweek.org/