Textbook Question
Label each of the following as either a physical process or a chemical process: (c) melting a piece of chocolate (d) burning fossil fuel (e) discharging a battery.
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Ch.1 - Introduction: Matter, Energy, and Measurement
Chapter 1, Problem 24
A silvery metal is put inside a beaker of water. Bubbles form on the surface of the metal, and it dissolves gradually. (b) Do you expect the remaining solution to be a pure substance or a mixture?
Verified step by step guidance1
Identify the metal: The problem describes a metal reacting with water, which is a common characteristic of alkali metals like sodium or potassium. These metals react with water to form a hydroxide and hydrogen gas, which explains the bubbles.
Understand the reaction: When an alkali metal reacts with water, it forms a metal hydroxide and releases hydrogen gas. For example, sodium reacts with water to form sodium hydroxide (NaOH) and hydrogen gas (H₂).
Analyze the solution: After the reaction, the metal hydroxide dissolves in water, creating an aqueous solution. This solution contains water and the dissolved metal hydroxide.
Define pure substance and mixture: A pure substance consists of only one type of particle, either an element or a compound. A mixture contains two or more different substances that are not chemically bonded.
Determine the nature of the solution: Since the solution contains both water and dissolved metal hydroxide, it is a mixture. The presence of more than one type of particle (water molecules and hydroxide ions) classifies it as a mixture, not a pure substance.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Chemical Reactions
When a metal reacts with water, it undergoes a chemical reaction, often resulting in the formation of a hydroxide and hydrogen gas. This process can lead to the dissolution of the metal, which is characterized by the formation of bubbles as hydrogen gas is released. Understanding this reaction is crucial to predicting the nature of the resulting solution.
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03:37
Chemical Properties
Pure Substances vs. Mixtures
A pure substance consists of only one type of particle and has a uniform composition, while a mixture contains two or more different substances that retain their individual properties. In the context of the question, the reaction of the metal with water produces a solution that contains dissolved metal ions and possibly other components, indicating that the solution is a mixture rather than a pure substance.
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01:03Solubility and Mixtures
Solubility
Solubility refers to the ability of a substance to dissolve in a solvent, forming a homogeneous solution. In this scenario, the metal's gradual dissolution in water suggests that it is soluble in water, contributing to the formation of a mixture. The extent of solubility can vary significantly among different metals, affecting the composition of the resulting solution.
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00:28Solubility Rules
Related Practice
Textbook Question
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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Textbook Question
A silvery metal is put inside a beaker of water. Bubbles form on the surface of the metal and it dissolves gradually. (a) Is this an example of a chemical or a physical change?
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Textbook Question
(a) Calculate the kinetic energy, in joules, of a 15-g bullet moving at 120 m/s.