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States of Matter - The Water Cycle

Grade 3IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Water is the only substance on Earth that naturally exists in three states: Solid (ice), Liquid (water), and Gas (water vapor).

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The chemical formula for a water molecule is H2OH_2O, meaning it consists of two Hydrogen atoms and one Oxygen atom.

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Evaporation: The process where liquid water is heated by the sun and turns into water vapor (gas).

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Condensation: The process where water vapor cools down in the atmosphere and turns back into liquid droplets, forming clouds.

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Precipitation: When water droplets in clouds become heavy and fall to Earth as rain, snow, sleet, or hail.

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Collection: The stage where water gathers in oceans, rivers, lakes, and underground reservoirs.

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Changes of state are driven by temperature: Water freezes into ice at 0∘C0^\circ C and boils into steam at 100∘C100^\circ C.

📐Formulae

H2OH_2O

Freezing Point=0∘C\text{Freezing Point} = 0^\circ C

Boiling Point=100∘C\text{Boiling Point} = 100^\circ C

💡Examples

Problem 1:

If a glass of liquid H2OH_2O is placed in a freezer set to −5∘C-5^\circ C, what state of matter will it become?

Solution:

Solid (Ice)

Explanation:

Since the temperature −5∘C-5^\circ C is below the freezing point of 0∘C0^\circ C, the liquid water will lose heat energy and freeze into a solid.

Problem 2:

You notice 'mist' forming on a cold window on a rainy day. Which part of the water cycle is this?

Solution:

Condensation

Explanation:

Warm water vapor in the air touches the cold surface of the window, cooling down and turning back into tiny liquid H2OH_2O droplets.

Problem 3:

Identify the state of matter for 'Water Vapor'.

Solution:

Gas

Explanation:

Water vapor is the gaseous state of H2OH_2O. It is usually invisible and moves freely in the air.