In this method, a low melting metal like tin can be made to flow on a sloping surface. In this way it is separated from higher melting impurities . This method is known as

Options

A. distillation
B. vapour phase refining
C. liquation
D. zone refining

Answer

To solve the question, we need to identify the method described for separating a low melting metal like tin from higher melting impurities. Here’s the step-by-step solution:

### Step 1: Understand the Process
The method involves using a low melting point metal, such as tin, which can be made to flow on a sloping surface. The key detail here is that the metal melts at a relatively low temperature compared to the impurities.

**Hint:** Consider the properties of melting points and how they can be exploited for separation.

### Step 2: Identify the Characteristics of the Method
When the low melting metal is heated above its melting point, it becomes liquid and flows down the slope. The higher melting impurities do not melt and remain stationary on the surface.

**Hint:** Think about how gravity and melting points can be used to separate materials.

### Step 3: Analyze the Options Given
1. **Distillation** - This method is used for separating components based on differences in boiling points, not melting points.
2. **Vapor Phase Refining** - This method involves converting a solid into vapor and then back to solid, which is not applicable here.
3. **Liquation** - This method specifically refers to the separation of metals based on their melting points, where a low melting metal is allowed to flow away from higher melting impurities.
4. **Zone Refining** - This method is used to purify materials by melting a small region and moving it along the material, which is not the same as what is described.

**Hint:** Focus on the method that specifically mentions the melting point and flow of a metal.

### Step 4: Conclusion
Based on the analysis, the correct method described in the question is **Liquation**. This method effectively separates a low melting metal from higher melting impurities by utilizing their differing melting points.

**Final Answer:** The method is known as **Liquation**.