Raven is filling a tray for her crystal collection. She stirs a spoonful of salt into warm tap water.
Rocket peers into the cup. "It vanished!" he says. "Your salt is gone."
"Is it?" Raven asks. "The water looks clear. What do you notice if we wait?"
Nova sets the cup on a sunny windowsill and dims her lights. "Here is a hint," she says. "Water can leave a cup as a gas. Can salt?"
Rocket taps his chin. "So we wait and watch," he says. "Patience is part of the plan."
When salt dissolves, water molecules pull tiny particles away from each salt crystal.
The salt particles spread out through the water. They are too small to see, so the water looks clear.
The salt did not disappear. It broke into particles too small for our eyes.
Leave salt water in an open dish for several days. The water slowly evaporates, which means it turns into a gas and goes into the air.
Only the water evaporates. The salt stays behind.
At the end, small square salt crystals are left on the bottom of the dish. That is strong evidence the salt was there all along.
| Statement | True or false? |
|---|---|
| When salt dissolves, it is destroyed. | ? |
| Dissolved salt particles are too small to see. | ? |
| When salt water evaporates, the salt goes into the air too. | ? |
When salt dissolves, water molecules pull tiny particles off each crystal.
Those particles spread through the water and are too small to see.
When the water evaporates, the salt particles stay behind and form crystals again.
Wonderful detective work. Things can hide in plain sight. Tomorrow we will find particles at work in the real world.