Identifying Non-Chemical Reactions

This question requires identifying the process that does not involve a chemical reaction from the given choices. To solve this, we need to differentiate between a chemical reaction and a physical change.

Understanding Chemical Reactions

A chemical reaction occurs when substances transform into new substances with different chemical properties. This typically involves the rearrangement of atoms and the breaking or forming of chemical bonds. Key indicators of a chemical reaction include:

• Formation of new substances (e.g., ash, new gases)
• Significant energy change (release or absorption of heat/light)
• Changes in color, odor, or state that indicate chemical alteration

Understanding Physical Changes

A physical change affects the form or appearance of a substance but not its underlying chemical composition. The substance remains the same at a molecular level. Common examples include changes in state, shape, size, or dissolving.

Analysis of the Options

Let's analyze each option provided:

1. Burning of coal: This is a combustion process where coal (mainly carbon) reacts chemically with oxygen in the air. The reaction produces new substances like carbon dioxide ($CO_2$), ash, and releases significant heat and light. Thus, it is a chemical reaction.
2. Digestion of food: Food digestion involves complex biochemical processes where large food molecules are broken down into smaller, absorbable molecules by enzymes and acids. These are a series of chemical reactions that alter the chemical composition of the food.
3. Burning of paper: Similar to burning coal, burning paper (made of cellulose) is a combustion reaction. Paper reacts with oxygen, producing gases (like $CO_2$, water vapor), ash, and releasing heat and light. This is a chemical reaction.
4. Conversion of water into steam: This process involves water ($H_2O$) changing its state from liquid to gas (steam) due to an increase in temperature. The chemical identity of water ($H_2O$) remains unchanged. This is a change of state, which is a physical change, not a chemical reaction.

Based on this analysis, the conversion of water into steam is the only option that represents a physical change and not a chemical reaction.