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Learning the scientific terms for when a solid disappears into a liquid.
Have you ever stirred a spoonful of sugar into a glass of water and watched it vanish? It didn't turn into a ghost—it's still there, just hiding! How does a solid 'disappear' into a liquid?
When you put a solid like sugar into a liquid like water and stir, the sugar seems to vanish. This process is called dissolving. But the sugar isn't actually gone! It has just broken down into pieces so tiny that your eyes can no longer see them. These tiny pieces spread out evenly throughout the water. In science, we call the solid that disappears the solute, and the liquid it hides in is the solvent. Even though you can't see the sugar, you know it is still there because if you took a sip, the water would taste sweet!
Let's look at how we make chocolate milk: 1. You start with a glass of milk (the solvent). 2. You add one spoonful of cocoa powder (the solute). 3. You stir the mixture. 4. The powder dissolves, turning the milk brown and delicious!
Quick Check
If you stir salt into water and it disappears, what is the scientific name for what just happened?
Answer
The salt dissolved.
Not everything can perform this 'disappearing act.' Solubility is a word scientists use to describe how well a substance can dissolve. If a solid can dissolve in a liquid, we say it is soluble. Salt and sugar are great examples of soluble solids. However, if a solid will not dissolve no matter how much you stir, it is insoluble. Imagine putting a plastic LEGO brick or a pebble into a glass of water. It stays solid and visible at the bottom. Those items are insoluble.
Imagine you have three cups of water and you add different things to them: 1. Cup A: You add sand. It sinks to the bottom. Sand is insoluble. 2. Cup B: You add honey. It mixes into the water. Honey is soluble. 3. Cup C: You add a metal paperclip. It stays the same. Metal is insoluble.
Quick Check
If a substance like a rock does NOT dissolve in water, is it 'soluble' or 'insoluble'?
Answer
It is insoluble.
Did you know you can change how fast something dissolves? Scientists have found that temperature matters! If you have a cup of water at (cool) and another at (hot), the sugar will dissolve much faster in the hot water. This is because the tiny particles in hot water move faster and 'kick' the solid apart more quickly. Stirring also helps because it moves the dissolved pieces out of the way so the water can reach the solid parts that haven't dissolved yet.
If you wanted to dissolve a large sugar cube as fast as possible, which steps would you take? 1. Break the cube into smaller grains to give the water more surface to touch. 2. Use very hot water () instead of cold water. 3. Stir the water rapidly with a spoon. By doing all three, the sugar dissolves in seconds instead of minutes!
What is the scientific term for a solid that CAN dissolve in a liquid?
Which of these items is insoluble in water?
Using hot water will usually make a soluble solid dissolve faster than using cold water.
Review Tomorrow
Tomorrow, look around your kitchen and try to name three things that are soluble and three things that are insoluble.
Practice Activity
With an adult's help, try dissolving one spoonful of salt in cold water and one in warm water. Which one 'disappears' first?