States of Matter

What is a solid?

A state of matter with a definite shape and volume (e.g., ice, proteins in crystal form).

What is a liquid?

A state of matter with a definite volume but no definite shape, taking the shape of its container (e.g., water, plasma).

What is a gas?

A state of matter with no definite shape or volume, expanding to fill any space (e.g., oxygen, CO₂ in respiration).

What is melting?

The phase change from solid to liquid by absorbing heat (endothermic).

What is freezing?

The phase change from liquid to solid by releasing heat (exothermic).

What is evaporation?

The phase change from liquid to gas at the surface of a liquid by absorbing heat (endothermic).

What is boiling?

The phase change from liquid to gas throughout the liquid at a specific temperature.

What is condensation?

The phase change from gas to liquid by releasing heat (exothermic).

What is sublimation?

The phase change from solid directly to gas (without becoming liquid) by absorbing heat (endothermic). Example: Dry ice (solid CO₂) turning into gas.

What is deposition?

The phase change from gas directly to solid (without becoming liquid) by releasing heat (exothermic). Example: Frost forming on a window.

: What are the two main categories of phase changes

Endothermic (absorbs heat) and Exothermic (releases heat).

Which phase changes are endothermic (require heat)? (My boiling vapor soaks heat.)

Melting, Boiling, vaporization, Sublimation

Which phase changes are exothermic (release heat)? (Freezing Cold Dogs)

Freezing, Condensation, Deposition

Why does sweating cool the body?

Evaporation absorbs heat from the skin, cooling it.

How is boiling different from evaporation?

Boiling occurs throughout the liquid at a specific temperature, while evaporation occurs only at the surface and at any temperature.

What happens to molecular movement when heat is added?

Molecules move faster, spreading apart, leading to a higher-energy state (solid → liquid → gas).

What happens to molecular movement when heat is removed?

Molecules slow down, coming closer together, leading to a lower-energy state (gas → liquid → solid).

What is plasma?

A high-energy state where gas particles are ionized

What phase change occurs when steam turns into water droplets?

Condensation (Gas → Liquid).

What phase change occurs when frost forms on a cold surface?

Deposition (Gas → Solid).

What phase change occurs when ice melts into water?

Melting (Solid → Liquid).

What phase change occurs when dry ice turns into CO₂ gas?

sublimation.

What phase change occurs when water vapor cools down to form rain?

Condensation (Gas → Liquid).

What is the mnemonic for remembering phase changes?

My Friend Eats Cold Soft Drinks

What are the three main states of matter relevant to biochemistry?

Solid, Liquid, Gas