Give the classification of matter when two substances exist with two phases present and the substance cannot be decomposed by chemical means.
a) heterogeneous mixture
b) homogeneous mixture
c) compound
d) element
The correct answer and explanation is :
The correct answer is: d) element.
Detailed Explanation:
To classify matter correctly, it’s important to understand two things:
- Phases present (solid, liquid, gas — visibly separate or uniform?)
- Chemical decomposition ability (can it be broken down into simpler substances by chemical means?)
The question states:
- Two phases are present (meaning you can see two distinct physical areas or forms).
- The substance cannot be decomposed by chemical means.
Let’s go through each option carefully:
a) Heterogeneous mixture
- A heterogeneous mixture has two or more visibly distinct parts (phases) and can be separated by physical means (e.g., salad, sand and water).
- However, a mixture is made of different substances, not a single pure substance.
- Since the question talks about a “substance,” not a mixture, this is not the right choice.
b) Homogeneous mixture
- A homogeneous mixture (like saltwater) looks uniform throughout (only one phase visible) even though it’s made of multiple substances.
- Here, two phases are visible, so this cannot be correct.
c) Compound
- A compound (e.g., water, H₂O) can be decomposed into simpler substances (elements) through chemical means (electrolysis of water splits it into hydrogen and oxygen).
- Since the question states it cannot be decomposed, it cannot be a compound.
d) Element
- An element is a pure substance that cannot be broken down into simpler substances by chemical means.
- Some elements can exist in different physical forms (allotropes) or different phases simultaneously. For example:
- Sulfur can exist as both solid crystals and molten liquid at the melting point.
- Carbon can appear as graphite and diamond under certain conditions.
- Two phases can simply reflect physical differences, but the chemical composition remains the same — it’s still a pure element.
Thus, because there are two phases but no possibility of chemical decomposition, the matter described must be an element.
Final Answer:
✅ d) element