Question

section 2.2 assessment
reviewing concepts

1. list seven examples of physical properties.
2. describe three uses of physical properties.
3. name two processes that are used to separate mixtures.
4. when you describe a liquid as thick, are you saying that it has a high or a low viscosity?
5. explain why sharpening a pencil is an example of a physical change.
6. what allows a mixture to be separated by distillation?

critical thinking

1. designing experiments how could you find out whether copper is harder or softer than the plastic used in a plastic cup?
2. inferring why would you expect the materials used to make pot holders to be poor conductors of heat?
3. applying concepts silicon dioxide is a solid at room temperature and methanol is a liquid. which substance has the higher melting point?

connecting concepts
organizing data in what order are the substances arranged in figure 12? use what you studied about organizing data in section 1.4 to explain why this order is useful. explain why you might choose a different order if you had similar data for 500 substances.

Explanation:

1. Answer - Explanation Format for Question 1:

• # Brief Explanations:
• Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical identity. Examples include color, odor, density, melting - point, boiling - point, hardness, and solubility.
• # Answer:
• Color, odor, density, melting point, boiling point, hardness, solubility

1. Answer - Explanation Format for Question 2:

• # Brief Explanations:
• Physical properties are used for identification (e.g., color to identify a mineral), for separation of mixtures (e.g., using density differences in centrifugation), and in material selection (e.g., choosing a metal with high conductivity for electrical wires).
• # Answer:
• Identification of substances, separation of mixtures, material selection

1. Answer - Explanation Format for Question 3:

• # Brief Explanations:
• Filtration is used to separate a solid - liquid mixture where the solid is insoluble in the liquid. Distillation is used to separate a liquid - liquid mixture based on differences in boiling points.
• # Answer:
• Filtration, distillation

1. Answer - Explanation Format for Question 4:

• # Brief Explanations:
• Viscosity is a measure of a fluid's resistance to flow. A thick liquid has a high resistance to flow, so it has a high viscosity.
• # Answer:
• High viscosity

1. Answer - Explanation Format for Question 5:

• # Brief Explanations:
• Sharpening a pencil changes its shape and size, but the chemical composition of the graphite and wood remains the same, which is the characteristic of a physical change.
• # Answer:
• Because it only changes the shape and size of the pencil without altering its chemical composition.

1. Answer - Explanation Format for Question 6:

• # Brief Explanations:
• Distillation separates a mixture based on differences in boiling points. The component with the lower boiling point vaporizes first and is then condensed and collected.
• # Answer:
• Differences in boiling points of the components in the mixture.

1. Answer - Explanation Format for Question 7:

• # Brief Explanations:
• One could use a scratch test. Try to scratch the plastic cup with copper and vice - versa. If copper can scratch the plastic, it is harder; if the plastic can scratch copper, copper is softer.
• # Answer:
• Perform a scratch test. Try to scratch the plastic cup with copper and the copper with the plastic cup to determine which is harder or softer.

1. Answer - Explanation Format for Question 8:

• # Brief Explanations:
• Pot holders are used to protect hands from heat when handling hot pots. Poor heat - conducting materials prevent heat from quickly transferring to the hands, providing insulation.
• # Answer:
• To provide insulation and protect hands from heat as poor conductors do not transfer heat easily.

1. Answer - Explanation Format for Question 9:

• # Brief Explanations:
• A solid at room temperature has a melting point above room temperature, while a liquid at room temperature has a melting point below room temperature. So, silicon dioxide has a higher melting point.
• # Answer:
• Silicon dioxide.

Answer:

1. Answer - Explanation Format for Question 1:

• # Brief Explanations:
• Physical properties are characteristics of a substance that can be observed or measured without changing the substance's chemical identity. Examples include color, odor, density, melting - point, boiling - point, hardness, and solubility.
• # Answer:
• Color, odor, density, melting point, boiling point, hardness, solubility

1. Answer - Explanation Format for Question 2:

• # Brief Explanations:
• Physical properties are used for identification (e.g., color to identify a mineral), for separation of mixtures (e.g., using density differences in centrifugation), and in material selection (e.g., choosing a metal with high conductivity for electrical wires).
• # Answer:
• Identification of substances, separation of mixtures, material selection

1. Answer - Explanation Format for Question 3:

• # Brief Explanations:
• Filtration is used to separate a solid - liquid mixture where the solid is insoluble in the liquid. Distillation is used to separate a liquid - liquid mixture based on differences in boiling points.
• # Answer:
• Filtration, distillation

1. Answer - Explanation Format for Question 4:

• # Brief Explanations:
• Viscosity is a measure of a fluid's resistance to flow. A thick liquid has a high resistance to flow, so it has a high viscosity.
• # Answer:
• High viscosity

1. Answer - Explanation Format for Question 5:

• # Brief Explanations:
• Sharpening a pencil changes its shape and size, but the chemical composition of the graphite and wood remains the same, which is the characteristic of a physical change.
• # Answer:
• Because it only changes the shape and size of the pencil without altering its chemical composition.

1. Answer - Explanation Format for Question 6:

• # Brief Explanations:
• Distillation separates a mixture based on differences in boiling points. The component with the lower boiling point vaporizes first and is then condensed and collected.
• # Answer:
• Differences in boiling points of the components in the mixture.

1. Answer - Explanation Format for Question 7:

• # Brief Explanations:
• One could use a scratch test. Try to scratch the plastic cup with copper and vice - versa. If copper can scratch the plastic, it is harder; if the plastic can scratch copper, copper is softer.
• # Answer:
• Perform a scratch test. Try to scratch the plastic cup with copper and the copper with the plastic cup to determine which is harder or softer.

1. Answer - Explanation Format for Question 8:

• # Brief Explanations:
• Pot holders are used to protect hands from heat when handling hot pots. Poor heat - conducting materials prevent heat from quickly transferring to the hands, providing insulation.
• # Answer:
• To provide insulation and protect hands from heat as poor conductors do not transfer heat easily.

1. Answer - Explanation Format for Question 9:

• # Brief Explanations:
• A solid at room temperature has a melting point above room temperature, while a liquid at room temperature has a melting point below room temperature. So, silicon dioxide has a higher melting point.
• # Answer:
• Silicon dioxide.