**Labelled Diagram of Sublimation of Ammonium Chloride**

A labelled diagram can help to illustrate the process of sublimation of ammonium chloride. Here is a brief description of the diagram:

1. Apparatus:
- A round-bottomed flask
- A Bunsen burner
- A delivery tube
- A test tube
- A cork with two holes
- A thermometer
- A beaker

2. Procedure:
- Place a small amount of ammonium chloride in the round-bottomed flask.
- Insert the thermometer and the delivery tube into the cork, ensuring they are tightly sealed.
- Attach the other end of the delivery tube to the test tube, which is placed in a beaker containing ice.
- Heat the round-bottomed flask gently using the Bunsen burner flame.

3. Labelled Diagram:
The labelled diagram should clearly show the different components of the apparatus and the direction of gas flow. It should also indicate the heating source and the cooling arrangement.

**Activity to Show Sublimation of Ammonium Chloride**

To demonstrate the sublimation of ammonium chloride, you can perform the following activity:

Materials:
- A small quantity of ammonium chloride
- A test tube
- A Bunsen burner
- A glass funnel
- A beaker

Procedure:
1. Place a small quantity of ammonium chloride in the test tube.
2. Attach the glass funnel to the mouth of the test tube, ensuring a tight seal.
3. Place the test tube in a beaker containing cold water or ice.
4. Heat the bottom of the test tube using a Bunsen burner flame.

Observations:
As the ammonium chloride is heated, it gradually sublimes, meaning it directly changes from a solid state to a gaseous state without passing through the liquid phase. The sublimation process is indicated by the formation of white fumes or a white solid deposit on the cooler parts of the test tube or the funnel.

Explanation:
Ammonium chloride undergoes sublimation due to its relatively low melting point and vapor pressure. When heated, the solid ammonium chloride molecules gain enough energy to break the intermolecular forces holding them together. As a result, they change into a gas and rise from the solid state directly to the gaseous state.

The cooling arrangement in the activity helps to condense the gaseous ammonium chloride back into solid form on the colder surfaces of the test tube or the funnel. This is why white fumes or a white solid deposit are observed.

Sublimation is a physical change where a substance directly converts from a solid to a gas without going through the liquid state. It is the reverse process of deposition, where a gas changes directly to a solid without becoming a liquid.