The correct answer is option 1: Burning of paper.

Burning of paper is an example of a chemical change because it involves a chemical reaction. When paper is burned, it undergoes a chemical reaction called combustion. In this process, the paper combines with oxygen in the air and is transformed into new substances, such as carbon dioxide, water vapor, and ash. This change is irreversible, meaning that once the paper is burned, it cannot be restored to its original form.

Option 2, which is the magnetization of soft iron, is an example of a physical change rather than a chemical change. The magnetization process involves aligning the magnetic domains within the iron, but it does not result in the formation of new substances.

Option 3, which is the dissolution of cane sugar in water, is also a physical change. Dissolving the sugar in water does not involve a chemical reaction; it only involves the sugar particles spreading evenly throughout the water.

Option 4, the preparation of ice cubes from water, is another example of a physical change. Freezing water to form ice cubes does not result in any chemical reactions; it only causes the water molecules to slow down and arrange themselves into a solid state.

Therefore, out of the given options, burning