Halloween is about all things spooky, slimy, gory and gross! So I bring to you; The Shrunken Heads Experiment! Sounds lovely, right? While this might creep some out, it is actually an awesome way to teach students about food preservation, bacteria and enzymes, while keeping in with the recent theme and festivities of Halloween. PLUS! The end result makes for perfect table decor, if Halloween is your thing!

Before I go ahead with the lesson plan, I would like to introduce some of my other recent Halloween themed educational posts:

Today's addition:

Shrunken Heads - Halloween Experiment (Learn About Food Preservation)

This is quite an open ended experiment and can be directed to accompany many theory lessons. I will however focus it at an angle where one can learn about food preservation and why thinks like salt and lemon juice can help prevent food from rotting. What ever reason you choose to do this activity for, it's super cool for kids to do and is very likely to stimulate an interest in science.

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The Experiment

What you will need:

Apples and potatoes (or similar fruits and vegetables)
A cup of lemon juice
Two tablespoons of salt
A suitable carving knife
Measuring cups and spoons

Instructions:

Start by carving your apples and potatoes like you would a pumpkin, to create a Jack o' Lantern.
You can leave the apple core in, or you could remove it. If yo plan on eating your shrunken heads (pretty creepy right), then I would recommend removing the core.
Add your lemon juice and salt to a jug and gentle mix.
Soak you apples and potatoes in the lemon and salt solution for over a minute, making sure the whole surface is covered.
This next step is determined by the amount of time you have on your hands. If you would like to get the experiment done quickly, then you can place them on a baking tray in a warm (not hot oven), until they start shrinking and drying out. If you would like the students/kids to witness the dehydration process and shriveling as it occurs, then you can set the apples and potatoes in a warm and dry place for a few weeks.

The end result will be a spongy and shriveled apple and shrunken and hardened potatoes. Use markers or pain (or other crafty materials) to spruce up your "heads" and make them as spooky as can be!

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The Lesson

Drying fruit and vegetables to keep them preserved and edible is an ancient practice. In this experiment we used salt and lemon juice as the substance which help preserve the food, but there are many other ways of preserving food stuffs, some healthy, some not so healthy!

So how does lemon juice and salt help prevent fruits and vegetables from rotting?

When a vegetable or fruit (take an apple for instance) is sliced open, you cut into the cells and as a result, enzymes are released.

Enzymes are macromolecular biological catalysts. Enzymes accelerate chemical reactions. The molecules upon which enzymes may act are called substrates and the enzyme converts the substrates into different molecules known as products. Wikipedia

When these enzymes are released they react with the oxygen in the air and as a result, the apples and potatoes etc. start to turn brown. This is when bacteria starts to settle on the produce and decomposition starts to occur.

Lemon juice is acidic and by adding it to the apple, you lower the pH of the apple. The acidity prevents the enzymes from reacting, and helps prevent bacteria from settling in.

Salt helps preserve food because it lessens the water available in the food for microbes to grow in. The combination of the two ingredients used in the experiment help to prevent the apples and potatoes from rotting and from remaining too wet.

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Source link: http://www.shareitscience.com/2017/10/shrunken-heads-halloween-science-experiment.html

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So that's one way you can learn about preserving food, although, the end result doesn't look too appetizing! Non-the-less, the kids will enjoy this activity from start to finish and will end up with a cool shrunken head that they can impress their friends with over Halloween!

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