Use the image to answer the question.

Question

An illustration shows several molecules in a space. There are five different types. There is one molecule with one O and two Hs. This is labeled water (H2O) traces. Another molecule has two Os and is labeled oxygen (O2) 21%. Another molecule has one C and two Os. This is labeled carbon dioxide (CO2) 0.04%. Another molecule has two Ns and is labeled nitrogen (N2) 78%. Another molecule has one Ar and is labeled argon (Ar) 0.9%.

The image depicts the composition of air. Use the image to explain why this statement is correct: “Mixtures are composed of different proportions of pure substances.”

Answer 1

The statement "Mixtures are composed of different proportions of pure substances" is correct, as illustrated by the varied composition of air depicted in the image. In this illustration, we can see that air is made up of several pure substances, each present in different proportions.

For instance, nitrogen (N2) constitutes approximately 78% of air, making it the most abundant component. In contrast, oxygen (O2) is the second most prevalent at 21%, followed by argon (Ar) at 0.9%. Carbon dioxide (CO2) and water (H2O) are present in much smaller amounts, at 0.04% and trace amounts, respectively.

These varying proportions highlight how a mixture, such as air, can contain different pure substances—each with its own distinct chemical identity—combined together. The specific ratios of these gases determine the characteristics of the mixture, demonstrating that mixtures are indeed made from varying amounts of different pure substances.