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Sugar and Salt Dissolve in Water · Stuff Can Change · dissolving [NGSS 2-PS1-1] · solids in water

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Sugar and Salt Dissolve in Water

with Atlas

Atlas stands at a sunny kitchen table with two clear glasses of water, a small spoon, a bowl of white sugar, and a shaker of salt. Atlas stirs one glass and watches closely as the sugar vanishes into the water, grinning with delight.

Identify what happens to sugar or salt when it is stirred into water.
Explain that dissolved sugar or salt is still in the water even when you cannot see it.
Predict whether stirring will make a solid dissolve faster.

Key terms

dissolve: when a solid spreads through water in pieces too tiny to see
solid: matter that keeps its shape, like a grain of sugar or salt
mixture: two things combined, like sugar spread all through water
stirring: moving water with a spoon to help a solid dissolve faster

Where Does the Sugar Go

When you drop sugar into water and stir, the sugar seems to vanish, but it does not really go away. The sugar breaks into pieces so tiny that your eyes cannot see them, and those pieces spread out evenly through every drop of the water. This spreading out is called dissolving. The sugar is still there the whole time; it has just become invisible inside the water.

How We Know It Is Still There

Even though you cannot see the dissolved sugar, there are ways to prove it stayed in the water. If you tasted the water, it would taste sweet, and that sweetness comes from the sugar spread through it. Salt works the same way and would make the water taste salty. The taste is proof that dissolving spreads a solid through water instead of destroying it.

Stirring Speeds It Up

Stirring the water with a spoon helps a solid dissolve much faster than just letting it sit. When you stir, the moving water bumps into the sugar and carries the tiny pieces away quickly, so they spread out sooner. Without stirring, the sugar still dissolves, but it takes more time. So if you want sweet water in a hurry, give it a good spin with your spoon.

Worked examples

Predict what happens when you stir salt into a glass of water.

Salt is a solid that can dissolve, just like sugar.
Stirring carries the tiny salt pieces all through the water.
The salt spreads out and disappears from view, making the water taste salty.

Answer: The salt dissolves and spreads through the water, which would then taste salty.

Hi there! I am Atlas, and today we are going to discover something amazing. Look at this spoonful of sugar. It is a solid — you can see it and touch it. Now watch what happens when I drop it into water and stir. The sugar seems to disappear! But here is the secret: the sugar did NOT go away. It spreads all through the water in pieces so tiny you cannot see them. Those tiny pieces mix into the water so completely that the sugar becomes invisible. We call this dissolving. When something dissolves, it mixes so well with water that you cannot see it anymore. How do we know the sugar is still there? If you tasted the water, it would be sweet. The sugar is still there — it is just spread through every drop. Salt does the same thing. Salt dissolves in water and would make it taste salty. Here is a bonus discovery: stirring helps things dissolve faster. Give your spoon a spin and see how quickly the sugar spreads!

Activity

Drag each solid into the glass of water and watch what happens when you stir

Practice

Predict whether stirring makes sugar dissolve faster or slower.

Explain how you could prove dissolved salt is still in the water.

Common mistakes to avoid

Dissolved sugar turns into water.The sugar does not become water; it stays sugar and just spreads through the water in tiny pieces.
Dissolving makes the sugar disappear forever.The sugar is still in the water, which is why the water tastes sweet even though you cannot see it.

Check your understanding

You put sugar in water and stir. The sugar seems to disappear. Where did the sugar go?

You dissolve sugar in water. How can you tell the sugar is still there?

What happens if you stir the water after dropping in sugar?

Recap

When sugar or salt dissolves in water, it breaks into pieces too tiny to see and spreads through every drop. The solid is still there, which is why the water tastes sweet or salty, and stirring helps it dissolve faster.

Reflect

What is something you have watched dissolve in a drink?