Bouncing Eggs – Potty Science Club
Hello and welcome to Potty Science Club Episode Five!
If this is the first time you have joined us you will find all our experiments are conducted in a home environment and not in a laboratory and will be safe and simple using equipment and items you can find in your own home. The experiments will reflect on an item or exhibit held in the Museum’s collections.
PLEASE NOTE. For this experiment, check with an adult about allergies, you may also need some adult supervision, and be warned that the experiment can produce some smelly (though harmless) gases!
The Potteries Museum has several collections of bird eggs, snail shells and sea shells. Bird eggs are the most fragile of the shell collections and need special care when handling but they also have some amazing qualities.
Although you may think there can be no connection between these different collections, they are all made up of Calcium carbonate, which is a common substance also found in rocks such as limestone, a type of sedimentary rock consisting mainly of calcite.
In this session of Potty Science, we will be using two common kitchen ingredients, one egg and a small bottle of vinegar. So, what will the experiment be looking at? Well, this experiment actually has three parts and several things will happen. For our first experiment you will need:
1. A clean glass jar or other clear container so you can see what’s happening
2. A bottle of vinegar (white vinegar is best so you can see what’s happening)
3. One egg
First, put the egg into the jar or container and add enough vinegar to cover the egg.
You will notice that the vinegar (which is also known as ethanoic or acetic acid) will start to react straight away with the egg shell, producing loads of bubbles as the calcium carbonate begins to dissolve producing carbon dioxide.
Vinegar is a mild acid. Eggshells are made of calcium carbonate – mix the two together and we get a chemical reaction. By soaking the egg in vinegar, we will see that the eggshell absorbs the acid, breaks down and dissolves. The calcium carbonate becomes carbon dioxide gas, which will dissipate into the air. Once the eggshell has dissolved, we will be left with the soft tissue lining of the inside of the eggshell. And amazingly we can make it bounce! Which is our next experiment.
After three days of soaking your egg, carefully remove it, you will notice that the egg is a bit bigger than when you first started (if you leave the egg too long you may have trouble getting it out of the jar). This is because some of the vinegar and water in the vinegar has moved through the membranes to the inside of the egg. This is called osmosis. Carefully wash the remaining shell off the egg
You will notice that your now naked egg feels rubbery.
Experiment 2 is simple – You can drop your rubber egg from several centimetres and see it bounce! Don’t go too high or you will break it (which will be messy!)
Take a look at the video to see how we did it!
For our final experiment, if you want to see your egg get really big, simply pop it into cold water and leave it. The water will move inside the egg through the egg’s membrane. This is called osmosis.
Osmosis equalizes the concentration of water on both sides of the egg membrane. Which means the egg will swell with the water and grow bigger. Remember, do not let your egg get so big that you cannot get it out of the jar, believe me this can happen!
You can shrink your rubber egg again by leaving it to dry.
Remember that at some time your egg will start to go off, and may become a bit smelly, so don’t keep it to long.
Happy eggs-perimenting, see you next time!
By Rob Gagliano, Casual Learning Development Leader and Natural Science Collections Volunteer