Gas mixing – fermentation

Gas mixing – fermentation

Short description
Full description
Short description

Gas mixing - fermentation

Type of resource:  Website

Web address

Language: English, Italian


How gases intervene in dough, biological fermentation.
How to create sourdough.

Scientific concept introduced

Sourdough, dough, microorganisms, glucose, fermentation, carbon dioxide, activators.

Creative and critical thinking

Critical thinking:
- Reasoning
- Prediction

Creative thinking:
- Imagination
- Curiosity
- Production

Mathematical reasoning


Scientific thinking

- Observing and making predictions

- Asking questions

- Analysing results

- Drawing conclusions based on experience

Learning how to learn

- Follow the instructions of an experiment

- Plan and organise work in time
- Describe the phases of a work
- Make hypotheses
- Recognise and argue changes in a substance
- Write the chemical formula of a gas
- Make a yeast


- Knowing how to work in a team
- Following safety rules
- Developing manual skills
- Sharing ideas

Full description

Gas mixing - fermentation

Overall aims

Organisation and planning over time
Developing observation and hypothesis skills
Developing ability to listen and follow instructions
Acquiring working methods of the scientific method
Improving scientific vocabulary
Identifying some simple chemical reactions that occur in everyday elements
Promoting the increase of manual skills
Promoting collaboration
Increasing the sense of self-efficacy

Vocabulary - keywords should be understood

Carbon dioxide

Expected learning outcomes (operational aims)

The child/student will be able to:
- follow the instructions of an experiment
- plan and organise the work in time
- describe the phases of a work
- make hypotheses
- recognise and argue changes in a substance
- write the chemical formula of a gas
- make a yeast

STEM skills - to which the learning unit is related to


- Observing and making predictions
- Asking questions
- Analysing the results of an experiment
- Drawing conclusions based on experience


- Knowing how to work in a team
- Following safety rules
- Developing manual skill
- Sharing ideas

Teaching methodologies/activity outline

Can you mix a gas? In the ingredient list of a recipe we usually only find solids and liquids... it never says to add a gas. Only apparently, because gases are essential to lighten many doughs.
How can a gas be generated in a dough? You need a leavening agent.
For thousands of years, yeast has been the only means known and used to make dough soft.
What are yeasts and how are they created? What do they have to do with gases? Yeasts are micro-organisms that take their name from the Latin verb "levare", meaning to raise.
Shall we discover together how the oldest yeast in the world is created and what it produces?
Mother yeast.


The pupils will be divided into small groups (3/4).
Each group will have to share the tasks from the beginning (kneading, documenting with smart phones or other means, planning the work and collecting information during the days of the activity).

1) Mix the flour with water and add a teaspoon of honey. Put this mixture into a glass jar. Close it with a damp gauze and wait 48 hours.

Note to the teacher: The children can be helped to plan the work through a series of questions.  What they have done
What they expect
Result at each stage
Questions raised

Natural (mother) yeast is created by allowing flour and water to acidify; it feeds on the sugars in the flour, triggering a fermentation process. To ensure success, we add honey (activator).

Stimulating questions:
Why honey? Can other activators be used?

2) After 2 days we weigh 100 g of dough, add 100 g of flour and 50 g of water, close with gauze and wait another 48 hours. Repeat at this rate for 10 days.

Note to the teacher:
When the dough starts to ferment, a chemical transformation takes place and 'bubbles' are created.
Biological (sourdough) fermentation is primarily a lactic fermentation; in addition to alcohol and carbon dioxide, lactic acid and acetic acid are also produced. Already after 48 hours, the dough should start to rise.
At the end of 10 days, the yeast should be quite liquid and full of bubbles.

Stimulating questions:
- How can I see that fermentation has started?
- Can I observe the carbon dioxide?
- Why does it smell sour, what is it? (because of the alcohol) What other aromas can we distinguish?
- Let us try to write down what we have observed in the form of a chemical formula.

At the end of the experiment, each group will be able to report their work to their classmates in a multimedia presentation, trying to give scientific reasons for what they observed and for the result obtained. What questions did the activity raise and how did you try to answer them?
What went wrong and why? What could have been done differently?

Note to the teacher:
We have learned to observe what is happening around us, not to take it for granted and to ask questions. We will never look at bread the same way again, now we know where it comes from! It is the
fruit of a long process... it needs an activator, to be started; inside there is something we did not expect and therefore were not able to see: a gas. Yeast is similar to us, we also need an activator to trigger a long process to allow us to grow!

Assessment of learning

Reflection on the experience, the processes, the group dynamics and what has been learnt;
Reconstruction, exhibition and evaluation of the products made;
Teacher self-assessment: by means of a satisfaction questionnaire and questions relating to strengths and weaknesses.

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

Glass jar
Smartphone or tablet

Kind of setting

Laboratory room or school kitchen

References - source

Bressanini, D. (2014), The science of pastry - the basics: the chemistry of the cream puffBonci
, G. (2012), The pizza game


Gas mixing - fermentation

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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