A chemical reaction happens when you add two substances together and they create new substances by rearranging their molecules. We can use a chemical reaction between acids and bases to make a “lava lamp”.

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Materials:

- Vegetable Oil

- Water

- Food Coloring

- Alka Seltzer

- Clear Bottle

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Procedure:

1. Add about 1 cup of water to the clear bottle.

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2. Add food coloring to the water in the bottle and mix it.

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3. Add a few inches of oil to the clear bottle. What happens? Do the oil and water mix?

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4. Break the Alka Seltzer into pieces and drop them into the bottle one at a time.

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5. Observe what happens!

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What’s happening? Alka Seltzer contains aspirin, sodium bicarbonate and citric acid. When added to water, the tablet begins to dissolve. The sodium bicarbonate splits apart to form sodium and bicarbonate ions that then react with the hydrogen ions from the citric acid. This causes the formation of carbon dioxide gas and water so we see bubbles!

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This is the formula for the chemical reaction:

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The oil is hydrophobic, which means that it doesn’t mix with the water. Water is denser than oil and sinks to the bottom. When the chemical reaction takes place in the water, the carbon dioxide bubbles that form are the least dense and rise to the top, releasing the gas into the air in the room. What happened after that? What happens when the Alka Seltzer stops reacting?

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