Classify each change as physical or chemical. a. Sugar burns when heated in a skillet. b. Sugar dissolves in water. c. A platinum ring becomes dull because of continued abrasion. d. A silver surface becomes tarnished after exposure to air for a long period of time.

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Identify the type of change: Physical changes involve changes in physical properties without altering the substance's chemical identity, while chemical changes involve a transformation into a different substance.

Analyze each scenario: a. Sugar burns when heated in a skillet. This involves a chemical change as sugar reacts with oxygen to form new substances like carbon dioxide and water.

b. Sugar dissolves in water. This is a physical change because the sugar molecules are dispersed in water but remain chemically unchanged.

c. A platinum ring becomes dull because of continued abrasion. This is a physical change as the dullness is due to physical wear and tear, not a change in chemical composition.

d. A silver surface becomes tarnished after exposure to air for a long period of time. This is a chemical change as silver reacts with sulfur compounds in the air to form silver sulfide, a new substance.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Physical Change

A physical change involves a transformation that does not alter the chemical composition of a substance. Examples include changes in state (like melting or dissolving) and changes in appearance (like grinding or cutting). In the context of the question, dissolving sugar in water is a physical change because the sugar retains its chemical identity.

Chemical Change

A chemical change results in the formation of one or more new substances with different chemical properties. This process often involves a reaction where bonds are broken and formed. In the question, burning sugar is a chemical change because it produces new substances, such as carbon dioxide and water, through combustion.

Tarnishing and Abrasion

Tarnishing is a specific type of chemical change that occurs when metals react with oxygen or other substances in the environment, leading to the formation of a tarnish layer. Abrasion, on the other hand, is a physical change that alters the surface texture of materials without changing their chemical identity. The dulling of a platinum ring due to abrasion and the tarnishing of silver are both important examples of these concepts.

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