Acid rain is a major environmental concern across the planet. The impact of acid rain on the environment and various ecosystems is well documented, but it may be difficult for students to see. As part of our environmental sciences studies, we have developed a special science experiment exploring the impact of acid rain on plants. The results were impactful and highly educational.
Acid Rain Science Experiment for Kids
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Acid Rain Experiment Video
Before we dive into the science behind acid rain and the details of this experiment. Here is a video of us conducting the experiment. If you can’t see the video, please turn off your adblockers. If you are still struggling to see the video, you can also find it on the STEAM Powered Family YouTube Channel.
Now, let’s explore what acid rain is, so we have a firm understanding of the science behind this issue affecting our environment.
What is acid rain?
Acid rain is rain or any other form of precipitation (snow, hail, even mist) that is unusually acidic, meaning that it has elevated levels of hydrogen ions and a low pH.
Acid rain, also called acid precipitation or acid deposition, is classified as acidic based on it having a pH of 5 or less. As a comparison, water, especially drinking water, has a neutral pH between 6.5 and 8.5. The more acidic the acid rain is, the lower its pH is. Acid rain can have harmful effects on plants, aquatic animals, and infrastructure.
Learn more about pH in our pH Lab.
Learn more about water pH, especially the pH of rainwater vs drinking water, in our Water Lab.
What causes acid rain?
Acid rain is primarily comes from the burning of fossil fuels. Burning fossil fuels in our cars, industry and and in the production of electricity and energy at power plants, produces harmful emissions, such as sulfur dioxide (SO2) and nitrogen oxides (NOx; the combination of NO and NO2).
There are natural contributors to acid rain. Rotting vegetation and erupting volcanoes release some chemicals that can cause acid rain, but most acid rain is a product of human activities.
How does acid rain form?
Acid rain is a popular expression for the more scientific term acid deposition. It refers to the way acidity can move from the atmosphere to the Earth’s surface. Although the most common way is through water (called wet deposition), it can also move through dust (this is called dry deposition).
When fossil fuels are burned they release emissions into the atmosphere. The atmosphere is a mixture of gases that surrounds the planet. On Earth, the atmosphere helps make life possible. Changes to our atmosphere are leading to climate change and life altering damage to our planet.
These emissions are toxic gases, mainly sulfur dioxide and nitrogen oxides. These gases then mix with water in the atmosphere, creating a chemical reaction and the result is acid rain. The acidic precipitation then falls back down to the Earth.
Here are the chemical reactions taking place in the atmosphere to make acid rain:
SO2 (sulfur dioxide)+ H2O (water) → H2SO4 (sulfuric acid) ←→ H+ (hydrogen ions)+ HSO4 (sulfuric acid) ←→ 2H+ (hydrogen ions) + SO42 (sulfate)
NO2 (nitrogen dioxide)+ H2O (water) → HNO3 (nitric acid) ←→ H+ (hydrogren ions) + NO3 (nitrate)
What are the effects of acid rain?
Acid rain can negatively affect everything in the environment, especially plants, aquatic animals and even human built infrastructure.
Acid deposition can reduce the pH of surface waters and lowers biodiversity. Biodiversity is critical to the health of our planet and the loss of that diversity negatively affects us all. Acid rain weakens trees and other plants, increasing their susceptibility to damage from stressors, such as drought, extreme cold/heat, climate change, and pests, which can lead to loss of vegetation.
Acid rain also depletes the soil of important plant nutrients, such as calcium and magnesium, which also contribute to the health of plants. It can also release aluminum, bound to soil particles and rock, in its toxic dissolved form.
Human built environments are not immune from the impact. Acid rain contributes to the corrosion of surfaces exposed to air pollution and is responsible for the deterioration of limestone and marble buildings and monuments. Ancient monuments are especially vulnerable.
What can we do about acid rain?
A great way to reduce acid rain is to produce energy without using fossil fuels. If people and industry started using renewable energy sources, such as solar and wind power this would result in a dramatic reduction in emissions. Renewable energy sources help reduce acid rain because they produce much less pollution.
We can also reduce our use of man made energy. Turn off the lights, computers and other electronics when not in use. Don’t waste water. Minimize the use of furnaces and air conditioning whenever possible (put on sweaters to warm up, or open windows to cool the house). Instead of driving take public transport, bike or walk. By conserving energy, we can substantially reduce emissions because less energy will need to be produced by the power plants.
Acid Rain Science Experiment
Now we have learned more about acid rain, let’s do a simple, but powerful science experiment with our young scientists. In this experiment we are using a different acid (we don’t want to use toxic gases around our students!), but the effect is still the same and profound.
Does acid rain affect plant growth science project
2 Large Jars
2 vials or small glasses
6 marbles (see below for details and alternatives)
Start by making sure your glasses or vials fit nicely inside the large jar with a flower inside of it. You can trim the flower stem as needed.
Fill the glass with water and place a flower in the glass.
Carefully place the glass with the flower inside the jar. Make sure the flower is not near the top of the jar. It should be cut so it sits just below the top.
Do exactly the same with the second jar. You now have of the same set ups. Let’s add our variable.
Pro Tip! To ensure you maintain your control or constant variables, make sure each flower is the same height, has the same number of leaves, and has the same amount of water in its’ glass.
This next step is a bit tricky. You can use a spoon or I used my fingers. Carefully pour about 1/2 cup of water into the jar, making sure not to get any on the flower or in the glass. It should just be in the bottom of the jar.
Cover the top of the jar with plastic wrap, place the marbles on top of the plastic wrap. The wrap just be just loose enough so the marbles make it drop a tiny bit. Secure the plastic wrap with an elastic. Use all the same coloured marbles, we used blue to indicate that this jar has water only inside.
Now repeat with the second jar, but instead of water, add 1/2 cup of vinegar to the bottom of the jar. Again being VERY careful not to get any vinegar on the flower or in the glass. Pour it only into the bottom of the jar.
Cover with plastic wrap, place three marbles on the plastic (we used green for acid/vinegar), then secure with an elastic.
Place both jars in the sun either outside or on a window ledge.
You will start to notice changes within a few hours, but we left ours for 24 hours. Due to the cool nights here, we did move the jars inside in the evening.
After 24 hours, remove the glasses with the flowers and observe the differences.
We used different coloured marbles to keep track of which jar was water and which one was vinegar. If you don’t have different coloured marbles, you can use some pebbles, erasers, or anything else that will provide a bit of weight. Just make sure you mark your jars in some way.
In this experiment we are looking at the effect of acid rain on our flowers. However instead of using toxic gases like the emissions from fossil fuels, we are using vinegar or acetic acid. The reason this works well is because acetic acid can evaporate and condensate just like water. Vinegar has a pH of between 2 and 4 depending on which type of vinegar is used. It is also readily accessible, natural, and non-toxic for students.
The marbles serve an important purpose. As the water and acetic acid evaporate in the warmth of the sun, it goes from liquid to gas. Once in the air, it creates condensation on the sides and plastic cover of the jar. The condensation is the gas returning to liquid form. This then drips back down onto our flower in it’s own little water cycle.
In this experiment we wanted to make sure the condensation on the plastic fell onto our flower and into the glass. By adding those marbles, it lowers the centre of the plastic, which causes the evaporation droplets to drip from the lowest point onto our flower which is placed in the centre of the jar.
The results were profound. As I mentioned earlier, we started noticing changes in our flowers but we decided to leave them for a full 24 hours. And I am very glad we did. Our observations would have not been the same had we stopped the experiment earlier.
Take a look at this before and after comparison of the two jars. Remember, the acid jar has green marbles on the left and the water jar has blue marbles on the right.
We started with two jars that has flowers of the same height, in a container with water. Our variable was whether it had water or vinegar at the bottom of the jar.
In the acid jar, the flower stem was completely wilted. The flower itself still looked OK, but the stem had lost all of its strength and integrity and could no longer stay upright. It had also started to yellow a little bit. It was a very, very sad looking flower.
Take a look at the results after 24 hours.
In the water jar, not only was our flower happy and strong, but it had actually grown in the 24 hours! We were shocked by this discovery. If we had stopped the experiment earlier, we would not have seen this, so I am happy we did the full 24 hours. The flower had actually grown a few centimeters and was now pushing up on the plastic. Our safe water filled environment provided our flower with the perfect conditions to grow and thrive.
A result that was so very, very different from the acid jar. Here are the flowers once we removed them from the jar.
During the experiment we took temperature readings with our infrared thermometer to see if there was any temperature differences in the jars that would account for the effect on the flowers, but the temperatures were consistent between the two jars.
This experiment was very easy to do, but the results had a profound effect and provided a powerful learning opportunity for students to learn about the effects of pollution and acid rain.
International Day of Clean Air
The atmosphere knows no borders, so the emissions released from one area, can travel long distances in our atmosphere, only to fall in other areas. That is why it is so important that we have International Clean Air Act initiatives to help protect all areas of our planet. The International Day of Clean Air is celebrated on September 7 every year.