Question

Can the relative amounts of the components of a mixture vary? Can the relative amounts of the components of a compound vary? Explain.

Short answer

Mixtures can have varying proportions, whereas compounds have fixed proportions.

Step-by-step solution

Understanding Mixtures

A mixture is composed of two or more substances physically combined. The relative amounts of these components can vary because there are no fixed proportions. Examples include salad, air, and saltwater where the quantities of ingredients can differ.

Understanding Compounds

A compound is a substance formed when two or more elements chemically bond in fixed proportions. The relative amounts of the components in a compound cannot vary. For example, water (H2O) always contains two hydrogen atoms for each oxygen atom, and this ratio remains constant.

Comparing Mixtures and Compounds

Comparing the two, the main difference is the variability in the relative amounts of their components. Mixtures can have varying proportions of their substances, whereas compounds have fixed ratios dictated by their chemical formulas.

Conclusion

Mixtures have variable relative amounts of components due to their physical combination. Compounds, however, have fixed proportions of their components because of their chemical bonds.

Key concepts

mixture composition

A mixture is formed when two or more substances come together physically. This means that the substances in a mixture retain their individual properties. Mixture composition is variable since there are no fixed proportions. For example, in a fruit salad, you can have more apples and fewer grapes, or vice versa. Similarly, air is a mixture of gases like nitrogen, oxygen, and carbon dioxide. You can have different amounts of these gases depending on the location and conditions.

Mixtures are categorized into two types:

• Homogeneous Mixture: The composition is uniform throughout, like saltwater.
• Heterogeneous Mixture: The composition varies, like a salad.

compound composition

A compound is a substance formed when two or more elements chemically bond together in fixed proportions. Unlike mixtures, compounds have a definite chemical formula, which determines the specific ratio of elements in them. For instance, water (H₂O) is always made up of two hydrogen atoms for every one oxygen atom. No matter where you find water, this ratio does not change.

Because compounds are chemically bonded, they have different properties compared to the individual elements they consist of. For instance, sodium (a metal) and chlorine (a gas) combine to form sodium chloride (table salt), which is a stable, edible compound with completely different properties from either sodium or chlorine.

chemical bonds

Chemical bonds are the forces that hold atoms together in a compound. These bonds form because atoms seek to obtain more stable electron configurations. There are two main types of chemical bonds:

• Ionic Bonds: Formed when electrons are transferred from one atom to another, resulting in oppositely charged ions that attract each other (e.g., sodium chloride).
• Covalent Bonds: Formed when atoms share pairs of electrons to achieve stability (e.g., water).

Chemical bonds make the composition of compounds fixed. Because of these bonds, changing the ratio of the elements would require breaking and forming new chemical bonds, effectively creating a different compound.

fixed proportions

Compounds are characterized by fixed proportions. This means that the elements within a compound always combine in specific ratios defined by their chemical formulas. For instance, carbon dioxide (CO₂) always has one carbon atom and two oxygen atoms.

These fixed proportions are a result of the need for elements to achieve stable electron configurations, leading to the formation of specific and fixed ratios. Because of these fixed ratios, the properties of a compound are uniform and predictable, no matter where you find them.

variable proportions

Unlike compounds, mixtures exhibit variable proportions. This means that the amounts of the different components in a mixture can vary. There are no set rules for the proportions of the substances in a mixture.

For example, in a mixture of sand and salt, you can have any ratio of sand to salt. The properties of the mixture can change depending on these proportions. This variability is why mixtures are often easier to separate into their individual components using physical methods like filtration, distillation, or magnetic separation.