Question

name: date: q1 chemistry u1l7 unit 1 review 3. which statement correctly describes a mixture? a. a mixture can consist of a single element. b. a mixture must have a uniform composition. c. a mixture can be separated by physical means. d. a mixture is always homogeneous. 4. one similarity between all mixtures and compounds is that both: a. are heterogeneous b. are homogeneous c. combine in a uniform fashion d. consist of two or more substance 5. name two processes that can be used to separate two clear, miscible liquids. when would a scientist choose to use one of these methods over the other? 6. *which property of a substance is used to separate the liquids in question #3? (a) melting point (b) density (c) boiling point (d) solubility 7. what method would a scientist use to separate sand from water? justify your response. 8. a scientist wants to separate oil from water. which separation method should they choose? (a) evaporation (b) chromatography (c) filtration (d) layer separation/decanting 9. justify your response to question #6.

Explanation:

1. A mixture can be separated by physical means. A mixture is composed of two or more substances that are not chemically combined and can be separated using physical processes like filtration, evaporation etc.
2. Both mixtures and compounds consist of two or more substances. Mixtures are physical combinations while compounds are chemical combinations.
3. Distillation and fractional distillation can be used to separate two clear, miscible liquids. Distillation is used when the boiling - point difference between the liquids is large. Fractional distillation is used when the boiling - point difference is small as it provides better separation through a fractionating column.
4. Boiling point is used to separate miscible liquids in distillation or fractional distillation. Different liquids have different boiling points and vaporize at different temperatures allowing for separation.
5. Filtration would be used to separate sand from water. Sand is insoluble in water and is a solid, so a filter paper can be used to retain the sand while the water passes through.
6. Layer separation/decanting should be chosen to separate oil from water. Oil and water are immiscible liquids with different densities, so they form separate layers and can be separated by carefully pouring off the top layer (decanting).
7. In distillation of miscible liquids, the liquid with the lower boiling point vaporizes first and can be collected after condensation, thus boiling point is the key property for separation.

Answer:

1. c. A mixture can be separated by physical means.
2. c. Consist of two or more substance
3. Distillation and fractional distillation. Distillation for large boiling - point differences, fractional distillation for small boiling - point differences.
4. C. Boiling point
5. Filtration. Sand is insoluble solid in water and can be retained by filter paper.
6. D. Layer separation/decanting
7. Boiling point is used in distillation to separate miscible liquids as different liquids vaporize at their respective boiling points.