Lesson 7 of 10
Keeping microbes from growing
Show on a big screenA jar of jam keeps for months on a shelf. What stops microbes growing in it?
Step 1 of 4
- Jam and salted fish hold a lot of sugar or salt.
- Sun-drying takes the water away.
- A fridge slows the microbes down.
- Heating kills many microbes. A tight lid keeps new ones out.
The rule
Jam keeps because it holds a lot of sugar. To preserve food is to keep it from spoiling for longer.
A lot of salt or sugar stops most microbes growing. A little does not.
| Way | What it does |
|---|---|
| Salt or sugar, a lot | Most microbes cannot grow |
| Drying | Takes away water |
| Cold | Slows growth |
| Heating | Kills many microbes |
| A tight lid | Keeps new microbes out |
Drying slows microbes because they grow faster with more water.
Add salt to the jar. Find where the microbes stop growing.
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Try the lab to finish this lesson.