Difficulty: Medium

Average Score: 70%

Which example describes a mixture?

Rationale

A substance with iron and nickel molecules combined but not bonded to each other.

This example illustrates a mixture as it consists of two different substances, iron and nickel, that retain their individual properties and are not chemically bonded. In a mixture, the components can be physically separated, unlike in compounds where atoms are chemically bonded.

A (A substance with sodium and oxygen atoms bonded to each other) YOUR ANSWER

This choice describes a compound, specifically sodium oxide (Na2O), formed by the chemical bonding of sodium and oxygen atoms. The atoms in a compound are chemically combined in fixed ratios, which distinguishes them from mixtures.

B (A substance with carbon and hydrogen atoms bonded together) YOUR ANSWER

Similar to choice A, this option refers to a compound, such as hydrocarbons like methane (CH4). The carbon and hydrogen atoms are chemically bonded, resulting in a distinct substance with specific properties, rather than a mixture of separate elements.

C (A substance containing only copper atoms) YOUR ANSWER

This choice represents a pure element, copper (Cu), instead of a mixture. While it consists of a single type of atom, a mixture requires the presence of two or more different substances that are not chemically bonded together.

D (A substance with iron and nickel molecules combined but not bonded to each other) CORRECT

This option accurately describes a mixture, where iron and nickel coexist without forming any chemical bonds. The individual properties of iron and nickel are maintained, and they can be separated physically, exemplifying the nature of mixtures.

Conclusion

A mixture is characterized by the physical combination of two or more substances that retain their individual properties and can be separated. In contrast, compounds are formed through chemical bonds, and pure elements consist of a single type of atom. The example of iron and nickel is an ideal representation of a mixture, highlighting how different substances can coexist without chemical interaction.

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