Salt Water Experiments

This week in science we have been learning about the aquatic biome and finding about salt water and fresh water habitats. We had a go at some salty experiments.

First the children mixed a salt solution and coloured it blue. This was carefully poured into a freshwater sample and we looked carefully to see the result. The denser salt water sank to the bottom.

Salt water (bluer) sinks to the bottom of the glass

Armed with this knowledge I set the children a challenge. I had 3 cups of water; 2 fresh and one salt. Using a syringe they had to identify which was the salt water.

3 samples - which is salt water?

R sucks some water up

The method involves sucking up a sample from one jar (don't fill the syringe), and then suck up a bit more from another cup.

If you have 2 freshwater samples the colours will mix.

If you suck up salt followed by fresh, the salt water will sink through the fresh water and the colours will mix.

However, if you suck up fresh followed by salt the salt water will stay at the bottom and the colours will not mix.

Red salt water stays at the bottom.

In the picture above L has used yellow fresh water then red salt water.

Red salt water  at the bottom

In the sample above R has tried yellow then blue waters (both fresh). They have mixed to make green. The red salt water was taken up last and stayed at the bottom.