Not all mixtures are solutions. When you mix something into a liquid and the pieces are big enough to see or eventually settle to the bottom, you have a suspension. Muddy water is a good example — tiny bits of dirt float around in the water for a while, but if you let it sit, the dirt slowly sinks to the bottom. Unlike solutions, suspensions look cloudy because the particles are big enough to block light. You can separate a suspension by letting it settle or by filtering it.
Have students make three mixtures: salt in water (solution), sand in water (suspension), and flour in water (suspension). Compare clarity, settle time, and whether filtering separates the mixture. Shake a jar of Italian salad dressing to show how oil and vinegar form a suspension that separates when left still.
You learned that a solution is a mixture where the solute dissolves completely and spreads out so evenly that the mixture looks perfectly clear. But not every mixture works that way. Sometimes the particles you add to a liquid are too big to dissolve. They float around, making the liquid look cloudy, and eventually they settle to the bottom. This kind of mixture is called a suspension.
Think about what happens when you stir dirt into a glass of water. The water turns brown and murky. Tiny bits of soil are floating throughout the water, bumping around and blocking light. But wait ten minutes and look again — the dirt is slowly sinking, and the water near the top is getting clearer. That settling is the telltale sign of a suspension. In a true solution, like salt water, nothing ever settles out no matter how long you wait.
Muddy puddles, flour mixed into water, and orange juice with pulp are all everyday suspensions. Italian salad dressing is a great example too. When you shake the bottle, the oil and vinegar mix together and the herbs spread throughout. Set it down and watch — within a minute, the oil floats to the top, the vinegar sinks below, and the herbs drift to the bottom. The ingredients never truly dissolved into each other; they were just temporarily pushed together by the shaking.
You can separate a suspension easily. Filtering works well — pour muddy water through a coffee filter and the dirt stays behind while clear water drips through. This would not work with a solution: if you filter salt water, the salt passes right through with the water because the dissolved particles are too tiny for the filter to catch. Settling is the even easier method — just leave the suspension alone and let gravity do the work.
Understanding the difference between solutions and suspensions matters in real life. Water treatment plants use settling and filtering to remove suspended dirt and germs from drinking water. Doctors need to know whether medicine is a solution or a suspension — suspensions must be shaken before use because the medicine particles settle to the bottom. Whenever you see "shake well before use" on a label, you are looking at a suspension.
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