Question

List two differences between a compound and a mixture.

Short answer

Compounds involve chemical bonding and fixed ratios, while mixtures are physically combined and separable by physical methods.

Step-by-step solution

- Define Compound

A compound is a substance formed when two or more chemical elements are chemically bonded together. The elements in a compound are present in a fixed ratio and cannot be separated by physical means.

- Define Mixture

A mixture is a material made up of two or more different substances which are physically combined. The components in a mixture can vary in proportion and can be separated by physical means.

- Identify Difference 1: Bonding

The first difference between a compound and a mixture is that in a compound, elements are chemically bonded together, whereas in a mixture, the substances are physically combined and no chemical bonding occurs.

- Identify Difference 2: Separation Methods

The second difference is that compounds cannot be separated into their constituent elements by physical methods, they require chemical reactions to be separated. In contrast, the components of a mixture can be separated by physical means such as filtration, distillation, or evaporation.

Key concepts

chemical bonding

Chemical bonding is the process by which atoms combine to form compounds. In a compound, atoms are held together by strong chemical bonds. These bonds can be covalent, ionic, or metallic depending on the elements involved. For instance, in water (H₂O), the hydrogen and oxygen atoms are bonded covalently. In an ionic compound like sodium chloride (NaCl), sodium and chloride ions are bonded together through ionic bonds.
Unlike compounds, mixtures consist of different substances that are physically combined. No chemical bonds are formed between the components in a mixture, hence they retain their own chemical properties.

separation methods

Separation methods help to distinguish between compounds and mixtures. In compounds, the elements are chemically bonded in a fixed ratio and cannot be separated by physical means. They require chemical reactions to break the bonds and separate the elements.
On the other hand, mixtures can be separated using various physical methods, including:

• Filtration: Separates solids from liquids in heterogeneous mixtures.
• Distillation: Separates liquids based on differences in boiling points.
• Evaporation: Removes a liquid from a solution to leave the solute behind.
• Magnetism: Removes magnetic materials from a mixture.

This shows that mixtures are easier to separate than compounds as they do not require chemical reactions for separation.

fixed ratio in compounds

In compounds, elements combine in a definite and fixed ratio. This means that the chemical formula of a compound always represents the same ratio of elements. For example, water (H₂O) always contains two hydrogen atoms for every one oxygen atom.
This fixed ratio is a key difference between compounds and mixtures. In mixtures, the proportion of components can vary; there is no fixed ratio. You can have different amounts of the substances mixed together, such as adding more sugar to water to get a sweeter solution. However, changing the ratio in a compound means creating a different compound altogether.
This concept is fundamental in understanding why compounds are pure substances with specific properties, while mixtures can vary widely in their composition and properties.