Science: Mixtures and Solutions
Identifying mixtures, solutions, solutes, and solvents
Science: Mixtures and Solutions
Identifying mixtures, solutions, solutes, and solvents
Chemistry - Grade 6-8
- 1
A student stirs table salt into a glass of water until the salt can no longer be seen. Is this mixture a solution? Explain why.
Think about whether the substances are evenly mixed throughout.
Yes, this mixture is a solution because the salt dissolves evenly in the water and forms a uniform mixture. - 2
In a cup of hot cocoa made from cocoa powder and water, the cocoa powder does not fully dissolve and some settles at the bottom. Is this a solution or not? Explain your answer.
This is not a true solution because the cocoa powder does not dissolve completely and the mixture is not uniform throughout. - 3
In salt water, identify the solute and the solvent.
The solvent is usually the substance present in greater amount.
In salt water, the salt is the solute because it is the substance being dissolved, and the water is the solvent because it does the dissolving. - 4
A trail mix contains raisins, peanuts, and chocolate chips. Is trail mix a homogeneous mixture or a heterogeneous mixture? Explain how you know.
Trail mix is a heterogeneous mixture because its different parts can be seen separately and are not evenly mixed throughout. - 5
Describe one way to separate sand from water. Explain why that method works.
Think about particle size.
One way to separate sand from water is filtration. This works because the sand particles are too large to pass through the filter, while the water can flow through. - 6
Sugar is stirred into warm tea until it disappears. What evidence suggests that a solution has formed?
The evidence is that the sugar is no longer visible and the tea looks the same throughout, which shows that the sugar dissolved evenly in the liquid. - 7
A student mixes oil and water in a beaker. After a few minutes, two layers form. What does this show about the mixture?
A solution stays uniform over time.
This shows that oil and water do not form a solution and instead make a heterogeneous mixture because they separate into visible layers. - 8
If more and more salt is added to water until no more salt dissolves, what is this type of solution called?
This type of solution is called a saturated solution because it contains as much dissolved solute as the solvent can hold at that temperature. - 9
Explain how evaporation can be used to separate dissolved salt from salt water.
Think about which substance can become a gas more easily.
Evaporation can separate dissolved salt from salt water because the water changes into vapor and leaves the container, while the salt remains behind as a solid. - 10
Air is made of several gases mixed evenly together. Is air best described as a solution, a homogeneous mixture, or a heterogeneous mixture? Explain.
Air is best described as a homogeneous mixture, and it can also be considered a solution of gases, because the different gases are evenly mixed throughout. - 11
A student says, "All mixtures are solutions." Is this statement correct? Explain why or why not.
Compare the meanings of mixture and solution.
This statement is not correct because all solutions are mixtures, but not all mixtures are solutions. Some mixtures are not uniform and their parts do not dissolve evenly. - 12
Give one example of a solution and one example of a heterogeneous mixture from everyday life. Explain the difference between them.
One example of a solution is lemonade with sugar dissolved in it. One example of a heterogeneous mixture is cereal in milk. The difference is that a solution is evenly mixed throughout, while a heterogeneous mixture has visibly different parts.