**Correct Option: A. Filtration** ### Detailed Explanation: To understand why filtration is the most suitable technique for separating a mixture of salt and sand, we need to consider the physical properties of both substances and how filtration works. 1. **Understanding the Mixture**: - **Salt (sodium chloride)** is soluble in water, meaning it can dissolve and form a solution. - **Sand (silicon dioxide)** is insoluble in water, meaning it does not dissolve and remains as solid particles. 2. **Filtration Process**: - Filtration is a separation technique that uses a filter medium (like filter paper) to separate solids from liquids or gases. - When a mixture of salt and sand is added to water, the salt dissolves, while the sand remains as solid particles. - By pouring this mixture through a filter paper placed in a funnel, the sand particles are trapped on the filter paper, while the saltwater solution passes through the filter and is collected in a container below. 3. **Why Filtration is Suitable**: - **Physical State**: Filtration is effective because it separates based on the physical state of the components. Sand, being solid, cannot pass through the filter, while the dissolved salt in water can. - **Ease of Use**: This method is straightforward and does not require complex equipment or conditions, making it practical for laboratory and educational settings. ### Why Other Options are Incorrect: **B. Distillation**: - **Explanation**: Distillation is a technique used to separate components of a mixture based on differences in boiling points. It is typically used for separating liquids or for purifying liquids. - **Why It's Weaker**: In the case of salt and sand, distillation would not be effective because it is not designed to separate solid particles from a liquid. Additionally, salt does not evaporate with water, so it would remain in the distillation flask. **C. Chromatography**: - **Explanation**: Chromatography is a technique used to separate mixtures based on the movement of different components through a stationary phase. - **Why It's Weaker**: This method is more suitable for separating colored substances or small amounts of compounds in a solution, not for separating solid particles like sand from a dissolved salt solution. **D. Centrifugation**: - **Explanation**: Centrifugation involves spinning a mixture at high speeds to separate components based on density. - **Why It's Weaker**: While centrifugation can separate solids from liquids, it is more commonly used for suspensions or emulsions. In this case, the sand would settle at the bottom, but it is not as efficient or straightforward as filtration for this specific mixture. ### Summary of Key Points: - **Filtration** is the best method for separating a mixture of salt and sand due to the solubility of salt and the insolubility of sand. - **Sand** is trapped by the filter, while **saltwater** passes through. - Other methods like **distillation**, **chromatography**, and **centrifugation** are not suitable for this specific separation due to their principles and intended applications. ### Revision Summary: - Filtration separates solids from liquids based on particle size. - Salt dissolves in water; sand does not. - Filtration is straightforward and effective for this mixture. - Other methods (distillation, chromatography, centrifugation) are not appropriate for separating salt from sand.