Which one among the following substances is a compound?

In chemistry, a compound is a pure substance formed when different elements combine in fixed ratios through chemical bonds, resulting in properties distinct from its constituents [4]. Sugar (sucrose) is a chemical compound with a specific molecular formula, whereas the other options are mixtures. Air is a homogeneous mixture of various gases like nitrogen, oxygen, and carbon dioxide [3]. Milk is classified as a complex mixture or colloid [3]. Tea is a mixture (infusion) where substances like sugar and tea extracts are physically mixed with water [3]. Unlike compounds, the components of these mixtures can be separated by physical means and do not exist in a fixed chemical ratio [4]. Therefore, sugar is the only substance listed that qualifies as a compound.

Sources

1. [4] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures > 8.1 What Are Mixtures? > p. 117
2. [2] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures > 8.3.2 Compounds > p. 124
3. [3] https://www.khanacademy.org/science/ms-chemistry/xc370bc422b7f75fc:classifying-matter/xc370bc422b7f75fc:mixtures/a/mixtures
4. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 8: Nature of Matter: Elements, Compounds, and Mixtures > 8.4 How Do We Use Elements, Compounds, and Mixtures? > p. 128