States of Matter Changes

Grade 3 · Science · Study Guide

Explore the three states of matter and how matter changes from one state to another when heated or cooled.

Everything around us is made of matter, and matter can exist in three main states: solid, liquid, and gas. A solid has a definite shape and volume, like an ice cube or a rock. A liquid has a definite volume but takes the shape of its container, like water in a glass. A gas has no definite shape or volume and spreads out to fill its container, like air in a balloon.

Matter can change from one state to another when it gains or loses heat energy. When a solid is heated enough, it melts into a liquid. This is called melting. Ice melting into water is a common example. The temperature at which a solid melts is called the melting point.

When a liquid is heated enough, it evaporates into a gas. This is called evaporation or vaporization. When water is boiled on a stove, it evaporates into steam. The opposite also happens: when a gas cools down, it condenses into a liquid. Condensation is why water droplets appear on a cold glass on a warm day.

When a liquid cools down enough, it freezes into a solid. This is called freezing. Water freezes into ice at 0 degrees Celsius. The opposite of melting is freezing, and the opposite of evaporation is condensation.

Sometimes matter can skip the liquid stage entirely. Sublimation is when a solid changes directly into a gas. Dry ice (frozen carbon dioxide) sublimates at room temperature. These changes in state are physical changes — the substance itself does not change, only its form.

Key terms

Solid
A state of matter with a definite shape and volume, such as ice or rock.
Liquid
A state of matter with a definite volume but no fixed shape; it takes the shape of its container.
Gas
A state of matter with no definite shape or volume that spreads to fill its container.
Melting
The change of state from solid to liquid when heated, as when ice becomes water.
Evaporation
The change of state from liquid to gas when heated, as when water becomes steam.
Condensation
The change of state from gas to liquid when cooled, as when water vapor forms droplets on a cold surface.

Flashcards

Solid
Matter that has a definite shape and volume; particles are tightly packed.
Liquid
Matter with a definite volume but no fixed shape; it flows and takes the shape of its container.
Gas
Matter with no definite shape or volume; particles spread out to fill any container.
Melting
When a solid is heated and changes into a liquid. Example: ice melting into water.
Freezing
When a liquid is cooled and changes into a solid. Example: water freezing into ice.
Evaporation
When a liquid is heated and changes into a gas. Example: water evaporating into steam.
Condensation
When a gas cools and changes into a liquid. Example: water vapor forming droplets on a cold glass.
Sublimation
When a solid changes directly into a gas without becoming a liquid first. Example: dry ice.

Questions

  1. When ice is heated and turns into water, what change of state has occurred?

    1. Freezing
    2. Condensation
    3. Evaporation
    4. Melting
    Show answer

    Answer: Melting

    Melting is the change of state from solid to liquid. When ice (solid) is heated, it melts into water (liquid).

  2. A liquid takes the shape of whatever container it is poured into.

    Show answer

    Answer: True

    Liquids have a fixed volume but no fixed shape, so they conform to the shape of whatever container holds them.

  3. When water vapor cools and turns into liquid water drops, this process is called ______.

    Show answer

    Answer: condensation

    Condensation occurs when water vapor (gas) loses heat energy and changes into liquid water droplets.

  4. Which of the following is an example of evaporation?

    1. A puddle of water drying up on a sunny day
    2. Ice forming on a window in winter
    3. A rock breaking apart
    4. A snowflake falling from a cloud
    Show answer

    Answer: A puddle of water drying up on a sunny day

    Evaporation is when liquid water absorbs heat and changes into water vapor (gas). A puddle drying up is a perfect example of evaporation.

  5. When matter changes state from liquid to solid, it gains heat energy.

    Show answer

    Answer: False

    When matter changes from liquid to solid (freezing), it LOSES heat energy. Gaining heat energy causes melting (solid to liquid) or evaporation (liquid to gas).

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