The correct option for separating a mixture of sand and salt is **A. Filtration**. ### Detailed Explanation 1. **Understanding the Mixture**: - The mixture consists of two components: sand and salt. Sand is a solid that does not dissolve in water, while salt (sodium chloride) is soluble in water. This property of solubility is key to choosing the right separation technique. 2. **Filtration Process**: - **What is Filtration?**: Filtration is a separation technique that uses a filter medium to separate solids from liquids or gases. In this case, we can use filter paper or a sieve. - **How it Works**: When the mixture of sand and salt is added to water, the salt dissolves, forming a saltwater solution, while the sand remains as solid particles. By pouring this mixture through a filter, the sand (solid) is trapped on the filter paper, while the saltwater (liquid) passes through. - **Final Steps**: After filtration, the sand can be collected from the filter paper, and the salt can be recovered from the saltwater solution by evaporating the water, leaving the salt behind. 3. **Why Other Options are Incorrect**: - **B. Distillation**: - Distillation is a technique used to separate components of a mixture based on differences in boiling points. It is not suitable for separating sand and salt because sand does not evaporate, and the process is more complex than necessary for this mixture. - **C. Chromatography**: - Chromatography is used to separate mixtures based on the movement of different components through a medium. It is typically used for separating colored substances or complex mixtures, not for solid-liquid separations like sand and salt. - **D. Centrifugation**: - Centrifugation involves spinning a mixture at high speeds to separate components based on density. While it can separate solids from liquids, it is not as straightforward or efficient for this specific mixture as filtration is. ### Example Calculation (if applicable): In this case, there are no calculations needed, but if you were to evaporate the saltwater to recover the salt, you could measure the mass of the salt before and after evaporation to determine how much salt was in the original mixture. ### Common Pitfalls: - **Assuming All Techniques are Equally Effective**: Students may think that any separation technique can be used for any mixture, but each technique has specific applications based on the properties of the components. - **Not Considering Solubility**: Failing to recognize that salt dissolves in water while sand does not can lead to choosing an inappropriate method. ### Revision Summary: - **Filtration is the best method for separating sand and salt due to the solubility of salt in water.** - **Sand remains solid and can be trapped by a filter, while salt dissolves and passes through.** - **Other methods like distillation, chromatography, and centrifugation are not suitable for this mixture.** - **Understanding the properties of the components (solubility, state of matter) is crucial for selecting the right separation technique.**