Experiment, Rivers, Seas and Oceans

Is water suitable for life?

Alkanity and acidity of water (pH) is an important factor in all kinds of chemical and biological processes. For e, in human body there are different organs, such as stomach, blood and cells, have defined pH range to keep up necessary physiological functions.

Change in the pH of water can seriously affect the lives of live organisms in a river. A lot of water organisms, including fish, invertebrates, plants and microorganisms, are very sensitive to changes in pH. These changes can be a result of natural processes, such as rainfall, snow melting or volcanic activity, but they can be also caused by human activity.

A few examples of how pH change can affect water organisms:

Water acidification: Sudden decrease in water pH can be a result of acid rains, that are created when atmospheric pollution, such as sulphur and nitrogen oxides, react with moisture in the air. Low pH can harm water organisms, decrease fish and other organisms reproduction and negatively affect water plants.

Water salinity: Introduction of salt water, for example due to sea waters access to river around an estuary, can change water pH and disturb a river ecosystem, affecting organisms that aren’t used to living in salt water. This is a phenomenon we’ve seen in Oder in 2022, when the pH suddenly increased and organisms in the river started to die en masse.

Industrial and farming pollution: Some of industrial and farming pollution can change water pH and cause acidification or alkalinity, that can be harmful to different life forms in river.

As you can see, the key task is to keep stable and appropriate pH in water ecosystems, to ensure good living conditions for organisms.

And now, lets check the pH of the water in a river using litmus paper (Warning! We didn’t have river water available, so we used rainwater instead).

Jak widać kluczowym zadaniem jest, aby utrzymywać stabilne i odpowiednie pH w ekosystemach wodnych, aby zapewnić dobre warunki życia dla organizmów. 

A teraz zbadajmy pH wody w rzece przy pomocy papierka lakmusowego (Uwaga! Nie mieliśmy pod ręką wody z rzeki, więc w ramach eksperymentu wykorzystaliśmy deszczówkę).


  • Learning dependencies of living in a river or different body of water to the level of pH.
  • Checking the river or different, available fresh water pH


Time: 15-30 minutes.

27.09 Dzien Rzek 4.1


  • Materials

    • Shot glass/ glass/ something to hold a liquid in
    • Litmus paper
    • Rainwater
    • Water from the tap


    • Boiled water
    • Mineral water
    • Vinegar
    • Any kind of drink

Course of the experiment

27.09 Dzien Rzek 4.3

The experiment is easy and interesting even for the adult. The teacher (or one of the kids, chosen as a volunteer) dips the litmus paper into the first sample – water from a river (in our case it’s rainwater) and puts it aside. To see which pH our sample has it has to rest up to a minute, until our paper changes colour. Neutral pH is yellow-green, acidic – red and alcaic – green.

In our case, the water from the tap, boiled water and rainwater have similar pH, that is about 7, mineral water was alkaline. If the teacher wants to show, how does the litmus paper reacts to the acidic pH, it is enough to add a few drops of vinegar into the water, it would instantly change the colour to an orange or red.

The phenomenon of acid rain is a common problem in places where the air is severely polluted. When the rain falls, it mixes with the pollution in the air and plants suffer, because there aren’t many plants that tolerate acidic ground (although it is true that some plants require acidic pH, but it’s a small group). You could try  to water a plant in a pot with acidic water and see that it not only grows poorly, but also is sick. We DO NOT recommend that!!!

We can extend the experiment and the teacher can suggest to check other liquids that a human drinks. We know now that human body, except few exceptions, has a neutral pH, so liquids we consume are most easily absorbed if they also have neutral pH. There are many possibilities: milk, Coca-Cola, coffee, compote. Kids should decide by themselves what they would like to check.

At the end of the experiment the teacher sums up with kids the results of the experiment.

14.11 Dzien Czystego Powietrza 1 E1668703355599

This post was created as part of a project co-financed by Deutsche Bundesstiftung Umwelt in cooperation with Naturschutzzentrum Oberlausitzer Bergland.

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