Which of the following is a characteristic of a pure substance?

• Its components can be separated by physical means.

• It has a uniform composition.

• Its components do not chemically combine in definite proportions.

• It has different chemical properties throughout.

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What property allows graphite to be used as a lubricant?

• It is a soft, black, powdery substance.

• Its carbon atoms form hexagonal rings that are loosely attracted and slide across each other.

• It easily conducts electricity.

• It is an elemental form of carbon.

How can a compound be broken down into its component elements?

• By physical means only.

• By chemical means only.

• By both physical and chemical means.

• Compounds cannot be broken down into their component elements.