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Hi class, I hope you are ready for our next lesson. Are you ready? 3, 2, 1, go!

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Today we are going to talk about the three main chemical reactions, ok?

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So, let's start.

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The first chemical reaction is combustion.

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When a substance gets in contact with oxygen, some energy is produced, for example light or heat.

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But, we need three different things to produce that combustion.

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We need fuel, for example wood.

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We need oxygen.

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And we need an energy, for example a hot environment.

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This process produces a new substance that, in the case of fire, is smoke or ash.

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The next one is oxidation.

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And it is when a substance that could be fuel or even metals gets in contact with oxygen.

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That produces a color change.

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In the case of metals, rust appears.

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Remember that rust is a reddish brownish substance that easily breaks apart and usually makes the original object useless.

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You have to remember that salt speeds it up.

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That's why that in the sea, if you have a house in the sea, you can see that those metal objects get rusty quicker than in magic, for example.

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The last one is fermentation.

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In this case, we don't need oxygen.

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We just need microorganisms that produce a sugar transformation.

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We have two types of microorganisms.

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We have fungi and bacteria.

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Fungi produces alcohol and carbon dioxide, while bacteria produces lactic acid and carbon dioxide.

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I hope everything is clear.

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If not, go through the unit and ask me your questions.