Burning fossil fuels releases carbon dioxide, CO2(g), which contributes to the greenhouse effect and hence to climate change. Burning some fossil fuels also releases nitrogen oxides and sulfur dioxides. These gases react with moisture in the airto produce acid precipitation: rain or snow containing dilute nitric acid and sulfuric acid. Precipitation is naturally acidic with a pH of 5.6 because carbon dioxide reacts with water to form carbonic acid. Precipitation is defined as being acidic if its pH is less than 5.6.
Acid precipitation has many effects on the environment, including the following:
- Lowering the pH of aquatic ecosystems affects fish’s gill’s ability to absorb oxygen. This can result in a decrease in numbers of some fish species.
- Damage to trees’ leaves leads to reduced resistance to disease and reduced ability to survive climate variation.
- Leaching of nutrients from soil results in poorer, less productive land.
- The toxicity of soils increases as the acid precipitation causes a release of toxic metals from rocks.
In aquatic ecosystems, the pH of surface water naturally ranges from 6 (slightly acidic) to 9 (slightly basic) depending on the biological activity and mineral content of rocks and sediment.
In this demonstration, students will compare the effects of acid on a number of objects to the effects of water. The beaker containing acid is a model of an environment exposed to acid precipitation.
Wear appropriate PPE: safety goggles.
Ask students, “How does acid rain affect plants, eggshells, and copper metal?” Invite students to justify their predictions.
Label one beaker “distilled water” and fill it about 2/3 full with distilled water.
- Label the other beaker “acid” and fill it about 2/3 full with vinegar.
- To each of the beakers add 1 leaf, 1 piece of eggshell, and 1 clean penny (Fig.1).
Fig.1 The “distilled water” beaker is the control.
- Cover the beakers and leave them overnight.
- The next day, invite students to observe and compare the contents of the beakers.
How did acid compare to the water in affecting the leaf, copper, and eggshells? Ask the students to revise their predictions, if necessary, based on what they have observed.
This activity is part of the STAO Demo Collection. The activities in this collection were specifically chosen because they are safe and a perfect fit for the Ontario curriculum. Be sure to check the rest of the activities at STAO Demo Collection