Why sand does not dissolve
Water particles cannot pull out strongly held particles.
Two tumblers
Potassium permanganate grains go into one tumbler of water. Sand goes into another. The pink colour spreads, but the sand stays as it is.
Why does the sand not dissolve?
What this lesson covers
The idea
A substance is insoluble in water when its constituent particles are held together so strongly that moving water particles cannot pull them out.
Two tumblers
Potassium permanganate grains go into one tumbler of water. Sand goes into another. The pink colour spreads, but the sand stays as it is.
Why does the sand not dissolve?
- Its particles are held together too strongly
- Sand is too heavy
- Water particles never touch sand
Can water pull them out?
Look at both grains among the moving water particles. Press Wait and watch.
Insoluble substances
Moving water particles pull out the particles of potassium permanganate from its grain and spread them. In many substances the constituent particles are held together so strongly that water particles are unable to pull them out. Such substances, like sand, are insoluble in water.
- Grain in water | What happens
- Potassium permanganate | Water particles pull its particles out: it dissolves
- Sand | Its particles are held too strongly to be pulled out: it is insoluble
Notes
A substance is insoluble in water when its particles are held together so strongly that moving water particles cannot pull them out, like sand.
Check yourself
What makes sand insoluble in water?
What do moving water particles do to a grain of potassium permanganate?
A substance does not dissolve in water even after a long time. What can you say about its particles?
- Its particles are held together so strongly that water particles cannot pull them out — correct. Yes. So the grain stays as it is.
- Sand has no particles. Sand is made of particles. They are held together very strongly.
- Water particles stop moving near sand. Water particles are always moving. They hit the sand but cannot pull its particles out.
- Push the whole grain up to the surface. The grain stays at the bottom. Its particles are pulled out one by one.
- Make the grain bigger. The grain gets smaller as its particles are pulled out.
- Pull its particles out of the grain and spread them — correct. Yes. That is how it dissolves.
- They are held together very weakly. Weakly held particles are easy for water particles to pull out.
- They are held together very strongly — correct. Yes. Water particles cannot pull them out.
- They are bigger than the container. Particles are extremely small. The reason is how strongly they are held.