18. Use the particle theory to explain why air is a solution but oxygen is a pure substance.
The particle theory states that all matter is made up of particles that are in constant motion and have space between them. A solution is formed when one substance (the solute) is dissolved in another substance (the solvent). In the case of air, it is a solution because it is a mixture of gases, such as oxygen, nitrogen, and carbon dioxide, all of which are evenly dispersed and mixed together in the air. Therefore, air is not a pure substance.
On the other hand, oxygen is a pure substance as it consists of only one type of atom and cannot be broken down into simpler components by physical means. It exists as a gas at room temperature and is not soluble in water or any other solvent. Therefore, it cannot be considered as a solution.
The particle theory can help explain why air is considered a solution while oxygen is considered a pure substance.
According to the particle theory, all matter is made up of tiny particles, such as atoms and molecules, that are constantly in motion. This theory states that substances can exist in different states of matter (solid, liquid, or gas) depending on the behavior and arrangement of their particles.
In the case of air, it is a mixture of gases, including nitrogen, oxygen, carbon dioxide, and other trace elements. These gases are not chemically bonded to each other and can be separated from each other through physical means, such as using filtration or distillation. Each gas in the air retains its individual properties and is considered a component of the mixture or solution.
On the other hand, oxygen, an element, exists as individual oxygen molecules (O2) and is classified as a pure substance. Oxygen molecules are chemically bonded together, and it cannot be broken down into simpler substances by physical means. It is a homogeneous substance with consistent properties throughout.
In summary, air is considered a solution because it is a mixture of gases where each gas retains its individual properties. Oxygen, being a pure substance, exists as chemically bonded oxygen molecules, making it distinct from a mixture like air.