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.

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.

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.

The graphic shows some examples of physical changes:

2.5c @McWhorterElem @LubbockISD sanding to show a physical change pic.twitter.com/rfOAL2qkMq

— Samantha Huston (@HustonsClasses) September 12, 2019

The kids loved burning Sucrose and looking at whether it's a chemical or physical change #WeAreGR pic.twitter.com/Uc4AU3HLok

— Coach Alicia Dutch (@GRHSgirlxctrack) September 13, 2019

 

• chemical change
• physical property
• chemical reaction
• composition
• atom
• molecule

Which of the following is not a physical change?

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