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Observing what happens when we put different solids into a cup of water.
Have you ever wondered why salt 'disappears' in a bowl of soup, but the sand at the beach stays crunchy under the waves?
When we put two different things together, we create a mixture. In our science lab today, we are mixing a solid (something that holds its shape, like a grain of sand) with a liquid (something that flows, like water). Water is often called by scientists. When you drop a solid into a cup of , you are making a mixture. Some solids like to stay exactly as they are, while others like to change their appearance completely!
Quick Check
If you put LEGO bricks into a bucket of water, have you created a mixture?
Answer
Yes! A mixture is any two or more things put together.
When you stir sugar into water, something amazing happens. The sugar seems to vanish! This is called dissolving. The sugar doesn't actually go away; it just breaks down into pieces so tiny that our eyes can't see them anymore. This special kind of mixture is called a solution. Even though the water looks clear, if you tasted it, you would know the sugar is still there because it would be sweet!
1. Take 1 cup of water (). 2. Add 1 spoonful of white sugar. 3. Stir for 30 seconds. 4. Observe: The sugar 'disappears' and the water stays clear. This is a solution.
Quick Check
What is the scientific word for when a solid breaks into tiny pieces and 'disappears' in water?
Answer
Dissolving.
Not every solid wants to join the 'disappearing act.' When you put sand into water and stir, the sand might swirl around for a bit, but it eventually sinks to the bottom. Sand does not dissolve. It stays as a visible solid. You can still see the individual grains of sand through the water. This is a mixture where the solid and liquid stay separate and easy to see.
1. Fill a jar with water. 2. Add 2 tablespoons of heavy sand. 3. Shake the jar vigorously. 4. Wait 1 minute. 5. Observe: The sand settles at the bottom. The water might look messy, but the sand is still there as a solid.
We can compare how many parts of a mixture we see. In a sugar solution, we see clear liquid. In a sand mixture, we see distinct parts: the water and the sand. Scientists use these observations to classify matter. If you have grams of sugar and mix it into grams of water, the total mass is grams, even if you can't see the sugar anymore!
Imagine you have two white powders: Salt and Flour. 1. You put Salt in Cup A and Flour in Cup B. 2. You add water and stir. 3. Cup A becomes clear (Salt dissolves). 4. Cup B stays cloudy and white (Flour does not dissolve well). 5. Conclusion: Salt creates a solution, while flour creates a cloudy mixture.
What happens to sugar when you stir it into water?
Which of these is a mixture of a solid and a liquid?
True or False: Sand dissolves in water just like sugar does.
Review Tomorrow
Tomorrow, try to remember: What is the special name for a mixture where the solid 'disappears' (like sugar water)?
Practice Activity
With an adult's help, try mixing different kitchen items like salt, pepper, or cocoa powder into water. Which ones dissolve and which ones stay visible?