Monday, December 15, 2014

Experimenting with Yeast as a Microorganism: Aligned with NGSS

1 packet of active dry yeast
1 cup of warm water
2 tablespoons of sugar
1 balloon
1 empty water bottle

Mix water, sugar and yeast in the bottle and place the balloon on top.  
Encourage students to set 
up several experiments using different combinations.  Try cold water. 
Try no sugar.  
Label each and record your results.  
Observe what happens. 

Questions for students:  
Do you think the yeast is alive?  
Will the same thing happen if we leave out the sugar?  
Why does the yeast need sugar?  
What is the gas inside the balloon?   
Why is yeast used when baking bread? 

Have students examine a piece of bread.  Record Observations.

Teacher Background Information:
The purpose of any leavening agent is to produce gas that makes the bread rise.  Yeast feeds on sugars and releases carbon dioxide in the process.  Yeast is tiny!  Just one gram holds about 25 billion cells!  That amount of fungi can produce a significant amount of carbon dioxide provided it has simple sugars to use as food.  As the yeast feeds on the sugar and produces carbon dioxide, the balloon fills up with this gas.   A similar process happens as bread rises.  Carbon dioxide from the yeast creates bubbles in the dough.  Once the bread has baked, this will give the loaf an airy texture. 

Science and Engineering Practices 
Planning and Carrying Out an Investigation
Constructing Explanations

Crosscutting Concepts
Cause and Effect
Stability and Change
Scale, Proportion and Quantity

Disciplinary Core Ideas
LS1 From Molecules to Organisms: Structure and Function
LS2 Ecosystems: Interactions, energy and dynamics

Below for you a printable for reading informational text.

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