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    Home » Science Experiments for Kids » Biology » What is Yeast?

    What is Yeast?

    Modified: Jun 16, 2021 · Published: Jan 21, 2012 by Emma Vanstone · This post may contain affiliate links · 4 Comments

    Yeast is a living single celled organism commonly used in baking. Yeast is a type of leavener ( baking soda and baking powder can also be used as leavening agents ). Yeast converts sugar and starch ( from the sugar and flour in the bread mix ) into carbon dioxide and ethanol. The carbon dioxide gas makes the dough rise. Yeast works best in a warm, moist environment, which is why it’s best to leave the dough somewhere warm to rise. This conversion of sugar into carbon dioxide and ethanol is called anaerobic respiration.

    We can see respiration occurring in yeast when we make bread or pizza dough.

    Note – respiration in yeast is anaerobic respiration – this means it doesn’t use oxygen

    Pizza Dough Respiration Investigation

    Pizza dough ingredients

    500g Strong White Flour

    7g Yeast (Fast)

    1tbsp caster sugar

    330ml Luke warm water

    1 tsp salt

    1tbsp olive oil

    How to make pizza dough

    • Mix the yeast, sugar and water in a jug and put to one side.
    • Sieve the flour into a mixing bowl and add a pinch of salt.
    • Gradually add the water until a nice elastic dough is formed.
    • Knead the dough well, strong flour will take a lot of effort to get nice and elastic, so work it hard.
    Pizza dough being kneaded by a child's hands
    Knead the pizza dough – image taken from Snackable Science
    pizza dough before rising

    Leave it somewhere warm, we left ours in the airing cupboard for about an hour. Look how much it increased in size.

    Pizza dough risen
    Pizza dough after rising

    Once risen, knead the air out of the dough again and roll it out to make your pizza bases.

    We turned our pizza into a plant cell model. The green peppers are chloroplasts!

    Pizza Plant Cell Model #plantcellmodel
    Pizza Plant Cell model

    More Yeast Experiments

    Did you know you can use the power of yeast to blow up a balloon? First blow up the balloon and let the air out. Pour a packet of yeast, warm water and a tablespoon of sugar into a small bottle and quickly pop the balloon on top. Give the mixture a shake and you should find the balloon blows up thanks to the carbon dioxide gas produced by the yeast.

    Image if yeast bread and pizza for a respiration experiment
    Yeast/Respiration Experiment for Kids

    Last Updated on June 16, 2021 by Emma Vanstone

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    Absorbing Experiments – Simple Science »

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    Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

    These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

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