Urban Ecology

Growing Bacteria

What it does

This experiment shows that temperature affects the growth of bacteria.

What you need

• Milk
• Measuring cup
• 2 small glass jars with covers
• Refrigerator

What to do

1. Pour one cup of milk in each jar and close the jars.
2. Place one jar in the refrigerator.
3. Place the other jar in a warm place
4. Observe the milk in each jar every day for 7 days.

What it's all about

The warm milk will become thick and lumpy, and it will smell sour. The cold milk should look and smell the same as it did in the beginning. Warm temperatures allow bacteria to grow faster, and bacteria cause food to spoil. Cold temperatures slow down bacterial growth. That is why we put food in the refrigerator. Even cold food will eventually spoil, but it will take much longer.

Remember, be sure you have a parent, teacher, or other adult help you!

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