YEAST DEMONSTRATION
1. Read Ann Morris's book, Bread, Bread, Bread. Discuss the idea that some of the foods
in the bread group may be flat, but some are raised, soft, and made up of small holes like
a sponge. This discussion about yeast will explain why.
2. Explain to the children that bread that is fluffy has a special ingredient called yeast.
Yeast is a living thing that eats and "breathes". When you buy yeast at a store it is
"resting" because the conditions are not right for being active. Show the children the
yeast from the package. It is dry and looks like grains of sand. When it is awakened it
will begin to breathe.
3. When we breathe out, our expelled air simply spreads out into the room, but we can
capture our expiration in a rubber glove to "see" it. Show the children what happens when
you breathe into a rubber glove.
4. Explain that if yeast "breathes", its expirations will simply spread out into the air,
unless we catch it somehow. Remind the children that once awakened, the yeast will
breathe. Because yeast is a tiny organism, it only gives out small expirations. Demonstrate
by breathing many small puffs of breath into the glove to eventually fill it.
5.. Explain that if we "wake up" the yeast with warm water, and feed it by giving it some
sugar, it will begin to breathe. Put the yeast into a jar or bottle with about an inch of
warm water. Add a spoonful of sugar. Swirl to mix. Now, explain that you will capture the
yeast's expirations with a rubber glove. Stretch the glove over the mouth of the
jar/bottle, squeezing out any air and securing at the base with an elastic band. Observe
over the next half hour as the yeast becomes active and bubbly, and the glove begins to
inflate.
6. Once the demonstration is complete, discuss the idea of catching the expirations
instead of letting them spread out into the room. In this demonstration the yeast
expirations were captured in a glove. When added to bread, the yeast is spread out into
the dough, and the many small puffs of expiration are captured by the bread dough, filling
it with many gas bubbles and making the bread fluffy like a sponge.
You will need:
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A packet of yeast (available in the grocery store)
A small, clean, clear, plastic soda bottle (16 oz. or smaller)
1 teaspoon of sugar
Some warm water
A small balloon
What to do:
1. Fill the bottle up with about one inch of warm water. (When yeast is cold or dry the
microorganisms are resting.)
2. Add the entire yeast packet and gently swirl the bottle a few seconds. (As the yeast dissolves, it
becomes active - it comes to life! Don't bother looking for movement; yeast is a microscopic
fungus organism.)
3. Add the sugar and swirl it around some more. Like people, yeast needs energy (food) to be
active, so we will give it sugar. Now the yeast is "eating!"
4. Blow up the balloon a few times to stretch it out then place the neck of the balloon over the
neck of the bottle.
5. Let the bottle sit in a warm place for about 20 minutes. If all goes well the balloon will begin to
inflate!
How it Works:
As the yeast eats the sugar, it releases a gas called carbon dioxide. The gas fills the bottle and
then fills the balloon as more gas is created. We all know that there are "holes" in bread, but how
are they made? The answer sounds a little like the plot of a horror movie. Most breads are made
using YEAST. Believe it or not, yeast is actually living microorganisms! When bread is made, the
yeast becomes spread out in flour. Each bit of yeast makes tiny gas bubbles and that puts millions
of bubbles (holes) in our bread before it gets baked. Naturalist's note - The yeast used in this
experiment are the related species and strains of Saccharomyces cervisiae. (I'm sure you were
wondering about that.) Anyway, when the bread gets baked in the oven, the yeast dies and leaves
all those bubbles (holes) in the bread. Yum.
From Early Childhood Science Technology and Engineering Standards; Practices,
Crosscutting Ideas, Disciplinary Core Ideas Draft; January 2013
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Observe and ask questions about observable phenomena (objects, organisms or events)
Plan and carry out investigations - Draw on prior knowledge and experience to predict what
might happen and inform investigations - Plan and implement investigations using simple
equipment; design/build a solution to a problem - Use senses and simple tools to observe,
gather, and record data (e.g., dictate, draw, photograph, write)
Make meaning from experience and data - Describe in many ways what happened during
an investigation or in building (engineering) - Talk and think about (reflect on) what
happened during an investigation or in solving a problem and why what happened might
have happened
Cause and effect: Identify cause and effect in events, relationships and patterns, (e.g. light
and shadows, force and moving things, temperature and melting ice; forces and building
collapse.)
Stability and change: Explore and reflect on events and things that change and those that
stay the same (e.g. buildings that stand and those that fall, melting, freezing, growth of
living things, seasons, apparent motion of the sun (seasons and seasonal change,
apparent motion of sun and moon).
From MA Guidelines for Preschool Learning Experiences
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Ask and seek out answers to questions about objects and events with the
Make predictions about changes in materials or objects based on past experience.
Observe and identify the characteristics and needs of living things: humans, animals, and
plants.
Investigate, describe, and compare the characteristics that differentiate living from non-living
things.
Use their senses of sight, hearing, touch, smell, and taste to explore their environment using
sensory vocabulary.