Which one of the following substances consists of small discrete molecules

Options

A. NaCl
B. Graphite
C. Copper
D. Dry ice

Explanation

To determine which substance consists of small discrete molecules, we need to analyze the options provided. Let's break down the reasoning step by step.

### Step 1: Identify the substances
We need to look at the options provided in the question. Common examples of substances that might be considered include dry ice (solid CO2), ionic compounds, metals, and covalent network solids.

### Step 2: Understand the nature of the substances
- **Dry Ice (Solid CO2)**: This is a molecular solid where the CO2 molecules are held together by weak van der Waals forces. Each molecule is discrete and separate from others.
- **Ionic Compounds (like NaCl)**: These consist of a lattice structure where ions are held together by strong ionic bonds, not discrete molecules.
- **Metals (like Copper)**: Metals have a metallic bonding structure, which involves a sea of delocalized electrons and does not consist of discrete molecules.
- **Covalent Network Solids (like Graphite)**: These have a continuous network of covalent bonds and do not consist of small discrete molecules.

### Step 3: Analyze the bonding in Dry Ice
Dry ice consists of CO2 molecules that are held together by weak van der Waals forces. This means that the individual CO2 molecules remain intact and do not form a continuous structure. Therefore, dry ice is made up of small discrete molecules.

### Conclusion
Based on the analysis, the substance that consists of small discrete molecules is **Dry Ice (Solid CO2)**.

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