Get two clear jars or cups and fill one with water and the other with rubbing alcohol. Using a waterproof (permanent) marker, write 2 of the same message – each on a sheet of tough paper (we used index cards). Gently fold or roll up the messages and soak them – one in each jar of solution. Now watch and see what happens over time.
What happens after 10 minutes? An hour? A day? (Different inks react differently, but most will gradually disappear over time in the alcohol, but stay legible in the water.)
Different liquids dissolve different substances. Alcohol can dissolve many inks while water cannot. You can watch other things dissolve differently between water and alcohol too.
Now Try This Dissolving Salt Experiment
Put some water in a mason jar and add salt to it. Stir it until the salt dissolves. Now put some rubbing alcohol into a second jar and add salt to it. Stir it and stir it, but it won’t dissolve. Alcohol can dissolve inks, but it can’t dissolve salt!
Alcohol is made up of different molecules than water. Salt dissolves in water and makes a solution. Molecules in the water invade the salt and pull it apart, making it seem to disappear (it hasn’t really disappeared though– it’s just broken down. If you tasted it you could clearly deduce that there is still salt in the water! You can also allow the water to evaporate over time and watch the salt reappear.) Alcohol can’t break the salt molecules down though. Alcohol is better at breaking down certain substances and water is better at others.
Try the same experiment using sugar. Which solutions does sugar dissolve in?
- You can go on any household tips websites to find hints on how to remove stains. You can tell what liquids dissolve things by reading the hints. Hairspray, alcohol, bleach, and various temperatures of water are all popular solvents for many household stains.
- You made ink disappear in this experiment, but why not try making invisible ink appear? Just write a message on a sheet of paper using lemon juice. To make it appear, heat it up under a hot lamp. The acid from the juice breaks down the paper and the part where you wrote the message will turn brown. This works with vinegar or other acids too.
- Heat often affects the way things dissolve. For example, you can dissolve more salt in hot water than in the same amount of cold water. Set up an experiment and test this out.