Challenge 4

CHALLENGE 4

There is water, but it is salty or muddy.
How to make water clean and safe?

Enjoy maths and sciences!

How to make clear water?

Conduct of the experiment:

by the Estonian school for the Italian school

Objectives of the experiment:

How to make muddy water to clear water.

Material:

You need: tubes ( 200 ml), water, soil (don't use
mineral-enriched soil for plants) , coffee filter, kettle.

1. Prepare in a test tube 200 ml of water and soil mixture (muddy water).
2. Allow the liquid to settle about 5 minutes. See what changes take place and write it down.
3. Filter the muddy water carefully through a coffee filter from one test tube to another. Make sure that the sedimentation stays in the first tube. What does the filtered water look like?
4. Boil the water, let it cool - and now you can taste it. How does it taste?

Organization of the classroom:

Students are divided into groups of 3-4 people. Each student has a role. It is important to make notes.

Additional explanations (prerequisite knowledge, preliminary observation):

Definitions: Sedimentation, filtration, cooking (to kill bacteria).

Conduct of the experiment:

1. Prepare in a test tube 200 ml of water and soil mixture (muddy water).
2. Allow the liquid to settle about 5 minutes. See what changes take place and write it down.
3. Filter the muddy water carefully through a coffee filter from one test tube to another. Make sure that the sedimentation stays in the first tube. What does the filtered water look like?
4. Boil the water, let it cool - and now you can taste it. How does it taste?

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How to make clear water?

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Pooling of results:

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by the Italian school from an Estonian experimental protocol

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Forecasts after reading the question:

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- As soon as we filtered for the first time we noticed a very dirty water. The colour was darker and there was a terrible smell! For this experiment, we used the same muddy water we obtained by a former experiments about the layers of the soil.

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- Gravels blocks the dirt in water
- Cotton blocks the dirt in water

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Conclusion:

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The experiment (videos or photos of students):

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- We noticed that all the dirt in the water was blocked by cotton, gravel and sand.
- Each time we changed water and materials, the water got clearer and clearer.
The process is long but we could understand how it is possible, especially for disadvantaged areas, to have clear water.

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Video HERE.

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Pooling of results:

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- As soon as we filtered for the first time we noticed a very dirty water. The colour was darker and there was a terrible smell! For this experiment, we used the same muddy water we obtained by a former experiments about the layers of the soil.

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Conclusion:

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- We noticed that all the dirt in the water was blocked by cotton, gravel and sand.
- Each time we changed water and materials, the water got clearer and clearer.
The process is long but we could understand how it is possible, especially for disadvantaged areas, to have clear water.

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How to make fresh water?

by the French school for the Icelandic school

Objectives of the experiment:

Model a system of desalination of water desalinisation to make fresh water.

Conduct of the experiment:

Material:

- water and salt to make saltwater
- a lamp to heat the water
- a small plastic bag (frozen bag for example)
- a small container
- an elastic band

Organization of the classroom:

By small groups or one experiment for the whole class.

Additional explanations (prerequisite knowledge, preliminary observation):

-

The experiment designs a system which is still exist. So then we could build it on our planet. Watch the video to know more.

Conduct of the experiment:

1. Mix the water and the salt to make saltwater (taste it to check salty flavour)

2. Put the small container in the plastic bag.

3. Form a buble shape with an elastic band.

4. Put over a lamp for heating water and make it evaporate. Wait 24 h and test the water fallen in the plastic bag.
Is the water still salted ?

How to make fresh water?

Pooling of results:

by the Icelandic school from a French experimental protocol

Forecasts after reading the question:

-the heat causes the water to evaporate and disappear into the air,
-the water and the salt disappear,
-the salt remains in the bowl,
-the water dissapears.

The experiment (videos or photos of students):

Students measured ½ dl of water and poured into a clear bowl. 1 tsp. of salt is put in and everyone was allowed to stir until all the salt had dissolved. Students then taste the salt water and taste a lot of salt. The students place the bowl in a bag with a zipper and everything, then place it in the heat under the lamp and let it stand.

After 24 hours, the situation is checked and it is observed that the bag is very wet inside and water has entered the bag outside the bowl. More than half of the water is still in the bowl. The experiment continues for the next 24 hours.

By the third day, the water had largely evaporated and salt was beginning to be seen in the little water that remained.

Conclusion:

Students complete the experiment and see that the water that was in the bowl has mostly evaporated, it has condensed on the plastic bag and flowed outside the bowl. Students taste the water in the bag and do not taste salt from it. They also taste the rest of the dish and find a great salty taste. Students also see the white salt left in the bowl.

The result is that water evaporates, not salt. It is possible to purify water by turning it into steam and then back into water.

Pooling of results:

Students measured ½ dl of water and poured into a clear bowl. 1 tsp. of salt is put in and everyone was allowed to stir until all the salt had dissolved. Students then taste the salt water and taste a lot of salt. The students place the bowl in a bag with a zipper and everything, then place it in the heat under the lamp and let it stand.

After 24 hours, the situation is checked and it is observed that the bag is very wet inside and water has entered the bag outside the bowl. More than half of the water is still in the bowl. The experiment continues for the next 24 hours.

By the third day, the water had largely evaporated and salt was beginning to be seen in the little water that remained.

Conclusion:

Students complete the experiment and see that the water that was in the bowl has mostly evaporated, it has condensed on the plastic bag and flowed outside the bowl. Students taste the water in the bag and do not taste salt from it. They also taste the rest of the dish and find a great salty taste. Students also see the white salt left in the bowl.

The result is that water evaporates, not salt. It is possible to purify water by turning it into steam and then back into water.