In basic chemistry, a change in which a substance undergoes a change only in its physical properties (such as state, shape, or size) but not in its chemical composition is called what?

Introduction / Context:
In school level chemistry, it is very important to distinguish between physical changes and chemical changes. Physical changes alter the form or appearance of a substance without changing its chemical identity, whereas chemical changes produce new substances with different compositions. This question asks you to recall the correct term for a change where only physical properties are affected and the substance remains the same chemically.

Given Data / Assumptions:

• The change affects properties such as state (solid, liquid, gas), shape, size, or physical appearance.
• The chemical composition and identity of the substance remain unchanged.
• No new substance with different composition is formed.
• Everyday examples include melting of ice, breaking of glass, or dissolving salt in water.

Concept / Approach:
A physical change is defined as a change in which one or more physical properties of a substance change, but its chemical composition stays the same. Physical properties include state, texture, colour, hardness, and size. In such changes, the molecules of the substance are not rearranged into different substances; they simply move or reorganise in space. A chemical change, by contrast, involves breaking and forming chemical bonds, creating new substances with different formulas and properties. Chemical and physical properties are characteristics, not types of changes. Therefore the correct term for the change described is physical change.

Step-by-Step Solution:
Step 1: Identify that the change described involves only physical properties, with no new substance produced. Step 2: Recall that a physical change affects properties like state, shape, and size, while maintaining the same chemical composition. Step 3: Recognise that chemical properties are descriptions of how a substance reacts, not the name of a process or change. Step 4: Recognise that chemical change is the term used when a new substance is formed and the composition changes. Step 5: Conclude that the term that fits the description is physical change.

Verification / Alternative check:
Consider melting ice to water. The ice changes from solid to liquid; its shape and state change, which are physical properties. However, the chemical formula remains H2O, and if the water is frozen again, it returns to ice, showing that the change is reversible and physical. In contrast, burning a piece of paper produces ash and gases that cannot be easily reversed to paper, and the composition has changed, so that is a chemical change. These examples show that the phrase in the question clearly matches the definition of physical change rather than chemical change.

Why Other Options Are Wrong:
- Chemical property: This refers to how a substance behaves in chemical reactions, such as flammability, not to a specific process of change.
- Physical property: This is a characteristic like density or colour; it is something that can change, but it is not the name of the change itself.
- Chemical change: This describes processes such as burning, rusting, or digestion, where new substances are formed. The question clearly excludes changes in chemical composition.
- Nuclear change: This term relates to changes in the nucleus, such as radioactive decay or nuclear reactions, which are not being discussed in this simple chemistry context.

Common Pitfalls:
Students sometimes confuse the terms property and change, or assume that any dramatic visible effect must be a chemical change. For example, dissolving salt in water looks like the salt disappears, but no new substance is formed, and the process is physical. It is important to ask whether the composition has changed and whether the process is easily reversible. If the chemical identity stays the same, the change is physical, not chemical.

Final Answer:
A change that affects only physical properties and not chemical composition is called a Physical change.