A CHEMICAL CURIOSITY

HYPOTHESIS

When water changes from liquid to gas by heating (evaporation) , the change is physical because we can readily change it back through cooling (condensation). Changing from solid to liquid is also a physical change. What is a chemical change?

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MATERIALS

1 Zip-Loc Sandwich Bag
1 Small Cup
1 Plastic Spoon
Vinegar
Baking Soda
Safety Goggles

PROCEDURE

1. Vinegar is an acid which can hurt if it gets into your eyes. So put on your safety goggles and keep them on during the experiment.

2. Put 2 heaping spoons of baking soda into the bag.

3. Fill the small cup with vinegar.

4. Carefully put the cup inside the bag and hold it so it does not spill.

5. Slowly squeeze out the air and close the bag very tightly. Be careful that the cup does not spill - hold onto it through the bag.

6. Now tip over the cup. What happens when the liquid meets the solid?

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CONCLUSION

Do you think this is a chemical change or a physical change and why?

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QUESTION

What evidence is there that a gas is present?

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