physical change


noun Chemistry.

a usually reversible change in the physical properties of a substance, as size or shape: Freezing a liquid is a physical change.

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Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

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What is a physical change?

A physical change is a change to the physical—as opposed to chemical—properties of a substance. They are usually reversible.

The physical properties of a substance include such characteristics as shape (volume and size), color, texture, flexibility, density, and mass.

Physical changes are not to be confused with chemical changes, which form whole new substances.

Physical change vs. chemical change

What do tearing paper, chopping wood, and boiling water all have in common? They’re all physical changes. Physical change is an important concept in chemistry; it describes changes to things that don’t result in brand-new substances.

Physical change upholds the molecular structure of a substance. Water, for example, is composed of two hydrogen molecules and one oxygen molecule, no matter whether it’s boiling or frozen. You can change the physical state of water (for example, going from liquid to frozen) without impacting its underlying molecular structure.

A chemical change, in contrast, does impact a substance’s molecular structure: one substance becomes another in a way that’s usually irreversible. The reaction of iron and oxygen forms a whole new substance: rust.

Dissolving salt in water is an example of a physical change. The salt crystals have changed their physical (not chemical) state, and if you evaporate the water by boiling it, the salt will recrystallize and “magically” appear in the bottom of the pot.

Physical changes are all around us. They happen when ice forms or when metals form an alloy, like bronze and stainless steel. The distinction between physical and chemical changes is also a foundational concept in chemistry.

Did you know ... ?

Can’t remember the differences in physical versus chemical change? Here’s a trick:

The initials of the phrase the very special cows meet daily stand for texture, volume, size, color, mass, and density. These are physical properties of a substance, and changes to them mark physical changes.

What are real-life examples of physical change?

The graphic shows some examples of physical changes:

ThoughtCo.com

What other words are related to physical change?

Quiz yourself!

Which of the following is not a physical change?

A. Wood catching fire
B. Crumpling paper
C. Melting ice
D. Dissolving sugar in water