Give the classification of matter when two substances exist with one phase present.
a) heterogeneous mixture
b) homogeneous mixture
c) compound
d) element
The correct answer and explanation is :
The correct answer is: b) homogeneous mixture
Explanation:
In chemistry, matter is anything that has mass and occupies space. It can be classified based on its physical and chemical composition into pure substances (elements and compounds) and mixtures (homogeneous and heterogeneous).
When two or more substances are combined physically (not chemically bonded) but only one phase is visibly present, it is known as a homogeneous mixture. A phase is a region of space throughout which all physical properties of a material are essentially uniform. If you observe a sample and it looks the same throughout, with no separate parts visible, it is a homogeneous mixture.
Examples of homogeneous mixtures include:
- Saltwater (salt dissolved evenly in water)
- Air (a mixture of gases like nitrogen, oxygen, and carbon dioxide)
- Alloys (such as brass, which is a mixture of copper and zinc)
In a homogeneous mixture, the different components are distributed uniformly at the molecular level. Even though multiple substances are present, they are so thoroughly mixed that the mixture appears as a single substance. The key point is that only one phase is visible.
Let’s quickly consider why the other options are incorrect:
- a) Heterogeneous mixture: This is when the composition is not uniform throughout. Different phases or parts are visible, like oil and water or a salad.
- c) Compound: A compound is a pure substance formed when two or more elements combine chemically in a fixed ratio. It is not a physical mixture and involves chemical bonding (e.g., water, H₂O).
- d) Element: An element is a pure substance consisting of only one type of atom (e.g., oxygen, O₂).
Thus, a homogeneous mixture is the classification when two substances are present but only one phase can be seen. It’s all about uniform appearance and even distribution at the microscopic level!