How yeast works? The Science Behind Yeast

How yeast works? The Science Behind Yeast

Short description
Full description
Short description

How yeast works? The Science Behind Yeast 

Type of resource:  Web page

Web address

Language: English


With just a few household items, we can see how the tiny fungi work to create those pockets of air that make bread so delightfully squishy.

Scientific concept introduced

Reactions, microorganisms, growth, gas production, fermentation.

Creative and critical thinking

Inductive thinking

Ability to observe and relate phenomena.

Mathematical reasoning

Measuring (keeping the proportions)

Counting (time in an analogic timer)

Scientific thinking


Ask questions

Analyze facts

Obtain conclusions

Learning how to learn

Active learning through experimentation and manipulation of different substances.


Learn to be cautious when handling substances that may react.

Full description

How yeast works? The Science Behind Yeast 

Overall aims

To develop the ability to observe and discover
To enhance the interest of experimenting and manipulating with different objects and materials.
To improve the ability to relate phenomena
To know the existence of small living beings that we can’t see
To demonstrate the presence of gases

Vocabulary - keywords should be understood

Little fungi, yeast, reactions, growth, sugar, gases, water, balloons, bottles, air, explosion, fermentation, bread cooking

Expected learning outcomes (operational aims)

To compare situations and recognize different elements

To explain a biological reaction

To carry out an experiment

To discover the existence of microorganisms

To recognize the presence of gas

STEM skills - to which the learning unit is related to

Asking questions

Analyzing and solving problems

Designing experiments

Drawing conclusions based on results

Motivation to learn and engage

Self-discipline and self-regulated learning (cognitive autonomy)

Relate facts and phenomena

Teaching methodologies/activity outline

With just a few household items, we can see how the tiny fungi works to create those pockets of air that make bread so delightfully squishy:


1 - Lest go to see what we need to start the experiment:

Give them the following elements: 2 bottles, 2 balloons, active dry yeast, a big glass of warm water, and a spoonful of sugar.


2 - Prepare and develop the experiment:

Students may prepare the two bottles with a little bit of warm water with sugar, then, they must add the yeast in one of the bottles and stir. In the other, they do not add it as a control. Finally, they should place the balloon on the neck of the bottle blocking the exit.


3 - Results of the experiment:

Wait a few minutes and observe what is happening.

Ask them what they think is going to happen. They should predict the balloon with yeast will inflate and get big the balloon. They also should think about why the control with only water and sugar do not inflate the balloon.

When they put their ear on the balloon, they can hear the bubbles as they formed and grew out of the jar and into the balloon. Soon the balloon will get so big that you should be worried if it explodes.


4 - Conclusion:
As the yeast eats the sugar, it releases a gas called carbon dioxide. The gas fills the bottle and, as more and more gas are produced, it fills the balloon.

In bread dough, the carbon dioxide from the yeast gets trapped in the gluten from the flour. The yeast dies in the hot oven leaving and the gluten solidifies leaving us with wonderfully soft bread!

Assessment of learning

Initial evaluation

Get to know the previous knowledge about fungi, microorganisms growth, gases, biological reactions, cooking fermentation procedures...

Continued evaluation

Think, create, elaborate explanations of the real phenomena.

Observe and explore the immediate, natural and physical environment, with an attitude of curiosity.

Use the oral language, gesture and images to express ideas. Listen and participate actively in regular situations.

Manifesting the necessary abilities to be able to listen, observe and interpret.

Final evaluation

To evaluate the learning objectives, use the chart in which the more important elements will be highlighted.

Equipment and materials to be used in learning unit (tools, ingredients etc)

- 2 bottles

- 2 balloons

- active dry yeast

- a big glass of warm water

- a spoonful of sugar.

Kind of setting

Preschool room

References - source


How yeast works? The Science Behind Yeast 

1. Usefulness for STEM education - integrating content of different disciplines

Cross-curricular character of the resource 


The range of S-T-E-M subjects included 


The presentation of possibilities of including artistic activities (STEAM approach)


2. Expected learning outcomes

Consistency (links) with preschool core curriculum


Communicativeness of description


3. Methodology of teaching

Clarity, communicativeness of instructions for teachers


Meaningful learning - using practical life problems


Original idea 


The level of ease in implementing the methodology to preschool age children


The level of ease in preparing necessary ingredients, materials and equipment needed


4. Sustainability

Ecological characteristics of materials/ results


Supporting healthy eating habits 


Low ecological footprint


Possibilities of inclusion (respecting cultural diversity and food intolerances)


5. Class management

Using differentiated forms of work - individual, team work etc.


Individual work





Team work





Whole group




6. Time management


Short activity (10-15 minutes)




Medium activity (20-30 minutes)




Long activity (1 hour or more)




Very long activity (1 day or more)

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