Limestone is a semiabsorbent rock which is basic, as opposed to acidic, in nature. Limestone experiments are frequently used in experiments to explore the properties of a harmful environmental phenomena known as acid rain. Limestone is effective in reducing small amounts of acidity in a liquid, which is a reason why it is used to make over-the-counter antacids.
Using Limestone To Heal Acid Rain
Discuss with the children the negative effects of acid rain on wild aquatic life. Tell them limestone is often used to help adjust the acidity of the water in wildlife ponds and lakes that receive acid rain. Lead the class in an observation of the effects of limestone in neutralising an acidic compound. For the acidic compound, mix 2 cups water and 1 tsp vinegar. Test the acid water solution with a garden soil pH test kit. to ensure the pH is 4. If the pH is less than 4, add a very small amount of baking soda until the reading is 4. If the solution is above a pH of 4, add a very small amount of vinegar until the reading is 4. Mark one of the bowls "limestone added" and mark the other bowl "no limestone." Place 1/4 cup of limestone in the limestone bowl. Then place 1 cup of the acid water solution in this bowl. Place the other cup of acid water in the bowl with no limestone. Measure the pH in each bowl with an garden soil pH test kit, record the figures and cover both bowls. Each day for six days, stir the solutions, allow the particles to settle, then record the pH levels. By the sixth day the bowl with limestone should be neutralised.
Limestone Acid Activity
Show the children how limestone used in a lake or pond causes the neutralisation in the water. Explain to the children that the limestone is broken down by the acid rain and produces a byproduct called calcium acetate. Place a glass cup of vinegar on one side, and pour a second glass cup containing water. Place a piece of limestone in each cup. Observe the effects. The limestone in the glass of vinegar should bubble and produce a layer of calcium acetate on the bottom, while the limestone in the water will not react at all.
Acid Fizz Test
Geologists often determine which rocks contain limestone using the acid fizz test. To lead the children in an experiment, place six different rocks on a counter top. Be sure to include pure limestone and marble which also contains limestone. Place a small piece of paper with the type of rock written on it, and place it upside down under each rock. Perform the acid fizz test by placing one or two drops of lemon juice on the rocks. Observe the effects closely using a magnifying glass. Help the students determine the results to see if they can guess which rocks contain the limestone.
Determine whether it is possible for a limestone rock to absorb water like a sponge. For this experiment, it is helpful to also use a rock that does not absorb much water, and a rock that absorbs a lot of water. According to the U.S. Department of Energy's Information Library, granite has a porosity of 1 per cent, limestone has a porosity of 15 per cent and pumice has a porosity of 50 per cent or higher. Set three glasses and label each granite, limestone or pumice. Measure enough water to just coat each rock, and write down the amount of water used for each glass. Place each rock in its corresponding glass and allow to sit for 45 minutes. Take the first rock out, allow all the water to drip from the rock and measure the water. Write this figure down and check the other two glasses in this way. To determine how much water was absorbed by each rock, subtract the end result from the beginning measurements.