Pure Substances and Mixtures

What is the definition of a pure substance in terms of its composition?

• A material made up of two or more different substances that are not chemically bonded.

• A material with a constant composition and distinct chemical properties.

• A mixture where the components are evenly distributed.

• A mixture where the components are not evenly distributed.

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Which of the following is an example of a homogeneous mixture?

• Sand and water

• Saltwater

• Oil and water

• Iron filings and sulfur

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Explain why saltwater is considered a homogeneous mixture.

• Because the salt and water can be easily separated by filtration.

• Because the salt and water are chemically bonded.

• Because the salt is evenly distributed throughout the water.

• Because the salt and water have different boiling points.

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What is the main difference between a homogeneous mixture and a heterogeneous mixture?

• The number of substances present.

• The ability to see the different components.

• The chemical properties of the substances.

• The physical state of the substances.

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Which of the following is a characteristic of a heterogeneous mixture?

• Uniform composition throughout.

• Components are chemically bonded.

• Components can be easily separated by physical means.

• Has a fixed boiling point.

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Describe a method to separate a mixture of sand and salt.

• Use a magnet to attract the sand.

• Dissolve the mixture in water, filter out the sand, and evaporate the water to recover the salt.

• Heat the mixture until the sand melts.

• Use chromatography to separate the components.

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What is the term for a mixture where the components are not uniformly distributed?

• Homogeneous mixture

• Heterogeneous mixture

• Pure substance

• Solution

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Which of the following is a pure substance?

• Air

• Water

• Salad

• Milk

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Which of the following mixtures can be separated by filtration?

• Saltwater

• Oil and water

• Sugar dissolved in water

• Sand and water

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Explain why oil and water form a heterogeneous mixture.

• Because oil is denser than water.

• Because oil and water have different boiling points.

• Because oil and water do not mix evenly and form separate layers.

• Because oil is a pure substance and water is a mixture.

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