The diffusion rate depends on the size of the substances

Answer

**Step-by-Step Solution:**

1. **Understanding Diffusion**:
- Diffusion is defined as the movement of molecules from an area of higher concentration to an area of lower concentration. This process continues until there is an equal distribution of molecules.

2. **Factors Affecting Diffusion Rate**:
- The diffusion rate is influenced by several factors, including:
- Concentration gradient: The difference in concentration between two areas. A steeper gradient results in a faster diffusion rate.
- Distance: The distance over which diffusion occurs. Shorter distances allow for faster diffusion.
- Size of the substance: Smaller molecules can diffuse more easily and quickly than larger molecules.

3. **Evaluating the Statement**:
- The statement in question is: "The diffusion rate depends on the size of the substances."
- Since smaller substances can diffuse more rapidly compared to larger substances, this statement is indeed true.

4. **Conclusion**:
- Therefore, the statement that "the diffusion rate depends on the size of the substances" is correct.

**Final Answer**: True

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