How many of the following are colloid? Sodium chloride, Starch solution, Cane sugar and Blood

Explanation

To determine how many of the given substances are colloids, we need to analyze each one based on the definition of colloids.

**Step 1: Understand the definition of a colloid.**
A colloid is a mixture where one substance (the dispersed phase) is evenly distributed throughout another substance (the dispersing medium). Colloids are characterized by the presence of large molecules or particles that do not settle out upon standing.

**Step 2: Analyze each substance.**
1. **Sodium chloride (NaCl)**: This is a salt that, when dissolved in water, forms a true solution. In a true solution, the solute particles are at the molecular or ionic level and do not scatter light. Therefore, sodium chloride is not a colloid.

2. **Starch solution**: Starch is a polysaccharide that can form a colloidal solution when mixed with water. In this case, the starch molecules are dispersed throughout the water, making it a colloid.

3. **Cane sugar (sucrose)**: Similar to sodium chloride, cane sugar dissolves in water to form a true solution. The sugar molecules are small and do not form a colloidal dispersion. Thus, cane sugar is not a colloid.

4. **Blood**: Blood is a complex fluid that contains cells, proteins, and other components suspended in plasma. The presence of these larger particles makes blood a colloid.

**Step 3: Count the colloids.**
From the analysis:
- Sodium chloride: Not a colloid
- Starch solution: Colloid
- Cane sugar: Not a colloid
- Blood: Colloid

Thus, out of the four substances, only **two** (starch solution and blood) are colloids.

**Final Answer: 2**

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