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

Problem 2

Chapter 1, Problem 2

Which of the following diagrams represents a chemical change?

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Understand the difference between a physical change and a chemical change. A chemical change results in the formation of one or more new substances with different properties, while a physical change affects only the physical properties without changing the substance's identity.

Look for signs of a chemical change in the diagrams, such as color change, gas production (bubbles), formation of a precipitate (solid), temperature change, or emission of light.

Identify if the diagram shows rearrangement of atoms or molecules into new substances, which is a hallmark of a chemical change.

Exclude diagrams that only show changes in state (like melting, freezing, or boiling) or shape, as these are physical changes.

Select the diagram that clearly depicts the formation of new substances or chemical reactions, indicating a chemical change.

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Key Concepts

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

Chemical Change

A chemical change involves the formation of new substances with different properties from the original materials. It usually involves breaking and forming chemical bonds, resulting in irreversible changes such as color change, gas production, or precipitate formation.

Physical Change

A physical change affects the form or appearance of a substance without altering its chemical composition. Examples include changes in state (like melting or freezing) or shape, and these changes are generally reversible.

Interpreting Diagrams of Chemical Processes

Diagrams representing chemical changes often show reactants transforming into different products, sometimes with indicators like bubbles, color shifts, or new substances. Understanding symbols and visual cues helps distinguish chemical changes from physical ones.

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Related Practice

Textbook Question

Which of the following figures represents (b) a mixture of two elements, (More than one picture might fit each description.)

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Textbook Question

Which of the following figures represents (c) a pure compound, (More than one picture might fit each description.)

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Textbook Question

Which of the following figures represents (d) a mixture of an element and a compound? (More than one picture might fit each description.)

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Textbook Question

Musical instruments like trumpets and trombones are made from an alloy called brass. Brass is composed of copper and zinc atoms and appears homogeneous under an optical microscope. The approximate composition of most brass objects is a 2:1 ratio of copper to zinc atoms, but the exact ratio varies somewhat from one piece of brass to another. (a) Would you classify brass as an element, a compound, a homogeneous mixture, or a heterogeneous mixture?

Consider the two spheres shown here, one made of silver and the other of aluminum. (a) What is the mass of each sphere in kg?

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Textbook Question

Consider the two spheres shown here, one made of silver and the other of aluminum. (a) What is the mass of each sphere in kg?

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