Rock Reactions
Materials:
- 1 pumice rock
- 1 limestone rock
- 2 pieces of chalk (long)
- 1 sensitive scale/ 1 spring scale
- 1 plastic bag
- 4 clear glass jars
- Vinegar
- Water
Instructions:
1. Take two of the glass jars and fill them halfway with vinegar.
2. Place the limestone rock inside one jar, and place the piece of chalk inside the other. What happens to the rock and chalk when it touches the vinegar?
3. Pull the limestone out after a few minutes. Pull the chalk out after an hour. When you pour the vinegar out of the jar, what do you notice at the bottom of the jar?
4. Take one of the other two glass jars. Fill it halfway with water. Place the pumice rock into the jar of water. What happens?
5. Take your second piece of chalk and weigh it. If you are using a spring scale, place the chalk into a small plastic bag so you can weight it. Record the weight.
6. Fill your last jar halfway with water. Place your second piece of chalk into the water and wait five minutes. Remove the chalk and weigh it again. Record the weight. Did it change?
This experiment shows you how certain rocks can react in different situations. In the first two situations (with vinegar), both the limestone and the chalk should bubble and react to being placed into the vinegar. This is because vinegar is an acid and it reacts with the carbonate in the limestone and in the chalk, breaking it down the same way acid rain and outdoor elements do to rocks. When you pour the vinegar out, you will see that there are sediments of limestone and chalk left behind in the jar. (*Note: Not all limestone has enough carbonate to bubble well, and that is why the chalk is used as well.)
The next situation involves pumice in water. When you place pumice in water, you will notice something strange happen. It will float! While most rocks do sink in water, pumice is an igneous rock which was subjected to extrusive cooling. In this rapid cooling process, the air did not get a chance to escape from the rock and became trapped inside. When placed in water, the trapped air acts like an inner tube. It keeps the rock afloat.
Finally, the chalk in water. You will notice that the chalk became heavier after being placed in water for several minutes. This is because the chalk absorbed the water! In this situation, the chalk acts the same way porous rocks do, absorb water and increase its weight. Try looking for rocks that absorb water. How much weight does each one gain?
Next Article: The Water Cycle
