Correct Option
The correct option is Glucose.
Explanation
Matter is broadly classified into pure substances and mixtures based on its chemical composition. A pure substance consists of particles (atoms or molecules) of only one kind and possesses a fixed chemical composition and distinct physical properties. Pure substances include elements and compounds.Option Analysis:
- Glucose Glucose (Correct): Glucose ($C_6H_{12}O_6$) is a chemical compound. It is formed by carbon, hydrogen, and oxygen chemically bonded in a fixed ratio by mass. Because it has a definite chemical formula and specific properties, it is classified as a pure substance.
- Brass Brass (Incorrect): Brass is an alloy, which is a homogeneous mixture of copper and zinc. While it appears uniform, its components are not chemically bonded in a fixed ratio, and it retains the properties of its constituent metals.
- Air Air (Incorrect): Air is a homogeneous mixture of various gases (nitrogen, oxygen, argon, carbon dioxide, etc.). Its composition is not fixed and can vary based on location and altitude.
- Tea Tea (Incorrect): Tea is a mixture (solution) containing water, extracts from tea leaves (tannins, caffeine), and other additives. It does not have a single chemical formula.
Key Takeaway:
Pure substances (elements and compounds) have a fixed chemical composition and sharp melting/boiling points. Mixtures consist of two or more substances physically combined in variable ratios and can be separated by physical methods.