Ch.1 - Introduction: Matter, Energy, and Measurement

Brown - Chemistry: The Central Science 15th Edition

Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo

Brown 15th Edition

Ch.1 - Introduction: Matter, Energy, and Measurement

Problema 24

Capitolo 1, Problema 24

A match is lit and held under a cold piece of metal. The following observations are made: (a) The match burns. (b) The metal gets warmer. (c) Water condenses on the metal. (d) Soot (carbon) is deposited on the metal. Which of these occurrences are due to physical changes, and which are due to chemical changes?

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Identify the definition of physical and chemical changes: Physical changes involve changes in state or appearance without altering the substance's chemical composition, while chemical changes involve the formation of new substances with different chemical properties.

Analyze observation (a): The match burns. This involves combustion, a chemical reaction where the match reacts with oxygen to form new substances like carbon dioxide and water.

Analyze observation (b): The metal gets warmer. This is a physical change as it involves a change in temperature, not a change in the chemical composition of the metal.

Analyze observation (c): Water condenses on the metal. This is a physical change as it involves a change of state from gas to liquid, without altering the chemical composition of water.

Analyze observation (d): Soot (carbon) is deposited on the metal. This is a chemical change as it involves the formation of a new substance (carbon) from the incomplete combustion of the match.

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Physical Changes

Physical changes are alterations that do not change the chemical composition of a substance. They involve changes in state, shape, or appearance, such as melting, freezing, or condensation. In the context of the question, the warming of the metal and the condensation of water are physical changes, as they do not involve a transformation of the substances involved.

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01:41

Physical Changes

Chemical Changes

Chemical changes involve a transformation that alters the chemical composition of a substance, resulting in the formation of new substances. This can include reactions such as combustion, where reactants are converted into products with different properties. In the scenario presented, the burning of the match and the deposition of soot are chemical changes, as they indicate a reaction that produces new materials.

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01:53

Chemical Changes

Energy Transfer

Energy transfer is a fundamental concept in chemistry that describes how energy moves from one system to another, often during physical or chemical changes. In this case, the heat from the burning match is transferred to the metal, causing it to warm up. This energy transfer is crucial for understanding the interactions between the match and the metal, as well as the resulting changes observed.

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01:26

Nature of Energy

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