States of Matter

Matter exists as solid, liquid, or gas. Particle motion changes with temperature, and melting, freezing, vaporization, condensation, and sublimation link the states. During a change heat rearranges particles so temperature stays fixed, and we note whether heat is absorbed or released. Move the temperature slider to see the particle model and follow the six state changes.

Three States of Matter

Temperature20℃

💡 Particle Motion Changes

①Solid: ordered arrangement, in-place vibration

②Liquid: free movement but particles stay near each other

③Gas: very fast random motion in all directions

④Higher temperature → more vigorous particle motion

Types of State Changes

🔍 Six State Changes

①Melting: solid → liquid (ice melts)

②Freezing: liquid → solid (water → ice)

③Vaporization: liquid → gas (water → vapor)

④Condensation: gas → liquid (vapor → droplets)

⑤Sublimation: solid ↔ gas (dry ice, frost)

State Changes and Heat

Absorbs Heat

Solid → liquid → gas: absorbs heat

Melting, vaporization, sublimation (solid→gas) absorb heat

Releases Heat

Gas → liquid → solid: releases heat

Condensation, freezing, deposition (gas→solid) release heat

🧊 Temperature During State Change

①During state change, temperature is constant

②Heat goes into rearranging particles, not raising temperature

③Boiling point: liquid → gas (water: 100℃)

④Melting point: solid → liquid (ice: 0℃)

Exam Key Points

Core Summary

State change ← absorption/release of heat

Heating absorbs, cooling releases

🎯 Exam Key Points

①Particle arrangement: solid vs liquid vs gas

②Six state changes and direction (absorb vs release)

③Temperature constant during change (mp, bp)

④Boiling vs evaporation: boiling throughout vs evaporation at surface

⑤Sublimation examples: dry ice, naphthalene, frost

Examples and Unit Test

Example 1

What is the change of state when ice melts into water, and does it absorb or release heat energy?

A change from solid to liquid is called melting (fusion).

In melting, particle motion becomes more active, so it absorbs heat energy.

▸ Melting / absorbs heat energy

Melting, vaporization, and sublimation (solid to gas) absorb heat; freezing, condensation, and deposition release heat.

Example 2

Why does the temperature stay the same while ice melts (at 0℃) even as you keep adding heat?

During a change of state, the added heat energy is used to rearrange the particles.

So it is not used to raise the temperature, and the temperature stays constant at the melting point (0℃).

▸ The heat is used to rearrange particles, so the temperature stays constant

During a change of state, heat goes into rearranging particles, so the temperature stays constant (melting/boiling point).

Unit-test style

Which statement about changes of state is correct?

①Vaporization is a change that releases heat energy

②Melting and vaporization are changes that absorb heat energy

③The temperature keeps rising during a change of state

④In a gas, particles vibrate in place

⑤Freezing is a liquid changing into a gas

▸ ② Melting and vaporization are changes that absorb heat energy

In melting (solid to liquid) and vaporization (liquid to gas), particle motion becomes more active and heat is absorbed.

Vaporization absorbs heat (①), temperature stays constant during a change of state (③), in a gas particles scatter quickly (④), and freezing is a liquid changing into a solid (⑤).

← Previous

Density

Molecular Motion

Was this helpful? Support seegongsik