The correct option is **A. Kerosene**. ### Detailed Explanation: 1. **Understanding the Options**: - **Kerosene**: This is a hydrocarbon fuel derived from petroleum. It is primarily composed of carbon (C) and hydrogen (H) atoms. Kerosene does not contain oxygen in its molecular structure. - **Soil**: Soil is a complex mixture of organic matter, minerals, gases, liquids, and organisms. While it may not have a fixed composition, it typically contains organic compounds that include oxygen, as well as minerals that may contain oxygen in their structures (like silicates). - **Glass**: Glass is primarily made from silica (SiO₂), which contains oxygen. Silica is a compound of silicon and oxygen, meaning that oxygen is a fundamental part of its structure. - **Cement**: Cement is made from a mixture of limestone (calcium carbonate), clay, and other materials. The chemical reactions involved in cement production (like the formation of calcium silicates) involve oxygen, and the final product contains compounds that include oxygen. 2. **Why Kerosene is the Correct Answer**: - Kerosene is a simple hydrocarbon, typically represented by the formula CnH2n+2 (for alkanes). For example, one common type of kerosene is C12H26. In this formula, there are no oxygen atoms present. Therefore, kerosene is entirely devoid of oxygen in its molecular structure. 3. **Why the Other Options are Incorrect**: - **B. Soil**: As mentioned, soil contains organic matter (like decomposed plants and animals) that includes oxygen. Additionally, minerals in soil often contain oxygen in their chemical structures. - **C. Glass**: Glass is made from silica, which is silicon dioxide (SiO₂). This compound contains oxygen, making it incorrect to say that glass is absent of oxygen. - **D. Cement**: Cement contains various compounds that include oxygen, such as calcium silicates and aluminates. The presence of these compounds means that cement cannot be considered free of oxygen. ### Common Pitfalls: - Students may confuse the absence of oxygen in a substance with the absence of oxygen in the environment. For example, while kerosene does not contain oxygen in its molecular structure, it can still react with oxygen when burned. - It’s important to differentiate between the chemical composition of a substance and the elements that may be present in mixtures or compounds. ### Revision Summary: - Kerosene is a hydrocarbon fuel that does not contain oxygen in its molecular structure. - Soil, glass, and cement all contain oxygen in various forms. - Understanding the chemical composition of substances is crucial for identifying the presence or absence of specific elements. - Always analyze the molecular structure of compounds when determining their elemental composition.