Fizzling Rocks! - A Study on Acid Precipitation

You have probably heard about the damage that acid rain or acid precipitation (snow, hail, sleet, etc.) can do to natural environments. Plants and animals live in a finely balanced ecosystem, and disturbing that ecosystem by introducing excess acid can have a detrimental effect.

Acidity is measured by using a pH scale. Neutral substances, such as water, have a pH of 7. Substances with a pH value less than 7 are ACIDIC; those with a pH value greater than 7 are BASIC. Some common acids are vinegar, pop and citrus juices. The closer the pH value gets to 7, the weaker the acid.

Here is a chart of common materials and their pH:

pH Substance
0
1 battery acid
2 lemon juice
3 vinegar, wine, pop, orange juice
4 tomatoes
5 coffee
6 saliva, milk
7 pure water (NEUTRAL)
8 shampoo
9 baking soda, antacids
10 milk of magnesia
11 household ammonia
12 hair remover (for drains)
13 oven cleaner
14

Natural precipitation has a pH of 5-6, so it is naturally acidic. However, when substances such as sulphur dioxide and nitrogen oxides are released into the air, they can combine with the moisture in the atmosphere to form very strong acids - sulphuric acid and nitric acid - with pHs of less than 5. This is harmful for the soil, water, trees, crops and buildings. These pollutants come from industries that burn oil and coal as sources of energy, as well as emissions from cars and other vehicles that use gasoline. Winds can carry the sulphur dioxide and nitrogen oxides great distances, so that the acid precipitation falls on areas where there is essentially no industrial activity.

One of the reasons that people are worried about acid precipitation is that damage it does to important structures - such as historical monuments. The following activity will allow you experiment on the effect that acid rain has on various building materials.

Let It Rain - Acid Rain!

Purpose: To observe the effects of acid precipitation on various building materials

Materials:

-vinegar
-eye droppers
-small rock samples: granite, limestone, marble, shale, sandstone, concrete/cement, other rocks in your area, brick
Rock samples can be obtained from science supply companies, or gathered from local building companies (e.g. Companies that make countertops, cemetery markers, patios)
-containers for your samples

Procedure:

1. Make an observation chart for the experiment. There should be four columns in your chart:
a) Rock type
b) Visual observations
c) Fizzling sounds?
d) Other

2. Place each sample in a container and make some visual observations. Write these observations in your chart. What colour is the sample? Are there any distinguishing marks or irregularities? Any patterns?

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