Changing States of Matter

1 The Basics: Solids, Liquids, and Gases

A diagram showing three jars. The first contains ice cubes with tightly packed dots (particles). The second contains water with loosely packed dots. The third contains a cloud of gas with dots spread far apart.

Everything around you—from your pencil to the water you drink—is made of matter. Matter is made up of tiny particles called atoms and molecules. How these particles move determines if something is a solid, liquid, or gas!

🧊 Solids

Solids have a fixed shape and volume. The particles are packed tightly together like a crowded elevator and only vibrate in place.

Examples: Ice, Wood, Metal

💧 Liquids

Liquids have a fixed volume but change shape to fit their container. The particles are close but can slide past each other.

Examples: Water, Juice, Milk

🎈 Gases

Gases have no fixed shape or volume. They expand to fill any space! The particles move very fast and are far apart.

Examples: Steam, Oxygen, Helium

🔬 Particle Behavior Comparison

State	Shape	Volume	Particle Movement
Solid	Fixed	Fixed	Vibrate in place
Liquid	Takes container shape	Fixed	Slide past each other
Gas	Fills container	Changes	Move freely & quickly

Key Facts

⚛️ All matter is made of tiny particles that are always moving.

📐 Solids keep their shape, while liquids take the shape of their container.

💨 Gases are the only state of matter that can easily change their volume (squish or expand).

2 It's All About Energy: Heat and Particles

A diagram showing a triangle of states of matter: Ice (solid), Water (liquid), and Steam (gas). Red arrows labeled 'Heat Added' point from solid to liquid to gas. Blue arrows labeled 'Heat Removed' point the reverse direction.

Matter is like a shapeshifter! 🧊 💧 💨 Whether something is a solid, liquid, or gas depends entirely on how much energy its particles have.

🔥 Adding Heat (Energy In)

When you add heat, particles get excited and move faster and further apart.

Melting: Solid ➔ Liquid.
Example: An ice cube turning into water.
Evaporation: Liquid ➔ Gas.
Example: Boiling water for pasta.

❄️ Removing Heat (Energy Out)

When you remove heat, particles lose energy, move slower, and clump together.

Condensation: Gas ➔ Liquid.
Example: Dew on grass in the morning.
Freezing: Liquid ➔ Solid.
Example: Making popsicles in the freezer.

🧪 Weird Science: Sublimation

Did you know? Sometimes a solid can turn directly into a gas, skipping the liquid phase entirely! This is called Sublimation. Dry Ice (frozen carbon dioxide) does this to create spooky fog effects!

Key Facts

🌡️ Temperature is actually a measurement of how fast particles are moving.

💧 Water freezes at 0°C (32°F) and boils at 100°C (212°F).

⚖️ When matter changes state, its mass stays the same (it doesn't disappear!).

3 Melting and Freezing: Solids and Liquids

A diagram showing a cycle between an ice cube and a water puddle. A red arrow pointing right says 'Melting (+ Heat)' and a blue arrow pointing left says 'Freezing (- Heat)'.

Have you ever wondered why your ice cream drips on a hot day or how puddles turn into ice skating rinks? It's all about energy! ⚡

🔥 Melting (Solid to Liquid)

Melting is the process where a solid turns into a liquid. This happens when a solid absorbs heat energy.

The particles start vibrating faster.
They break away from their fixed positions.
Example: An ice cube turning into a puddle of water at 0°C (32°F).

❄️ Freezing (Liquid to Solid)

Freezing is the reverse! It is the process where a liquid turns into a solid. This happens when a liquid loses heat energy.

The particles move slower.
They lock into a fixed, rigid structure.
Example: Making fruit juice popsicles in the freezer.

💡 Did you know? For pure water, the melting point and the freezing point are exactly the same temperature: 0°C (32°F)! If you add heat, it melts. If you remove heat, it freezes.

Comparison: What's the difference?

Feature	Melting 🍦	Freezing 🧊
Direction	Solid ➡️ Liquid	Liquid ➡️ Solid
Energy	Heat is Added (Gained)	Heat is Removed (Lost)
Particle Speed	Speed Up	Slow Down

Key Facts

🔥 Melting requires gaining heat energy.

❄️ Freezing requires losing heat energy.

🌡️ Water freezes and melts at 0°C (32°F).

4 Evaporation and Condensation: Liquids and Gases

A split illustration showing a boiling kettle producing steam (evaporation) on the left, and a cold glass of lemonade with water droplets forming on the outside (condensation) on the right.

Have you ever wondered why puddles disappear after the rain, or why a cold soda can gets wet on the outside? It's all about energy and moving particles! 🏃‍♂️💨

🔥 Evaporation (Liquid ➡️ Gas)

Evaporation happens when a liquid turns into a gas. This usually requires heat energy.

Imagine the particles in a cup of water. When they heat up, they start moving faster and faster. Eventually, the particles on the surface get so much energy that they break free and float away into the air as water vapor!

☀️ Example: Wet clothes drying in the sun.
🍝 Example: Boiling water for pasta (rapid evaporation).

❄️ Condensation (Gas ➡️ Liquid)

Condensation is the opposite! It happens when a gas turns back into a liquid. This occurs when gas particles cool down.

When water vapor in the air touches a cold surface, the particles lose energy. They slow down, come closer together, and turn back into liquid water droplets.

🥤 Example: Water droplets on a cold drink.
🌫️ Example: Fog on the bathroom mirror after a shower.

🔄 The Great Exchange!

Feature	Evaporation	Condensation
Change	Liquid to Gas	Gas to Liquid
Energy	Heat is added (Gets warmer)	Heat is lost (Gets cooler)
Particles	Speed up & spread out	Slow down & clump together

Key Facts

♨️ Evaporation turns liquid into gas when heat is added.

💧 Condensation turns gas into liquid when it cools down.

☁️ Clouds are actually made of tiny liquid droplets formed by condensation!

5 Skipping Steps: Sublimation and Deposition

A diagram showing two processes: on the left, a block of dry ice turning into fog (Sublimation), and on the right, water vapor forming ice crystals on a leaf (Deposition).

Usually, matter follows the rules: solids melt into liquids, and liquids boil into gases. But sometimes, matter is in a hurry and skips a step completely! 🏃💨

🔥 Sublimation (Solid ➔ Gas)

Sublimation occurs when a solid turns directly into a gas without ever becoming a liquid puddle. This requires a lot of energy (heat)!

Real Life Example: Dry Ice!
Dry Ice is frozen carbon dioxide. At room temperature, it doesn't melt—it sublimates into a cool, spooky white fog. This is used in stage effects! 🎭

❄️ Deposition (Gas ➔ Solid)

Deposition is the exact opposite. It happens when a gas turns directly into a solid. This happens when heat is removed very quickly.

Real Life Example: Frost!
On a freezing morning, invisible water vapor in the air touches cold grass or windows and instantly turns into ice crystals (frost) without becoming water first. 🌿

Comparison: The Shortcuts

Process	Change	Energy Needs
Sublimation ⬆️	Solid ➔ Gas	Needs Heat (Absorbs Energy)
Deposition ⬇️	Gas ➔ Solid	Loses Heat (Releases Energy)

Key Facts

💨 Sublimation turns a solid straight into a gas.

❄️ Deposition turns a gas straight into a solid.

⚗️ Dry Ice and Frost are the most common examples.

6 Conservation of Mass: Matter is Never Lost

A split illustration showing a balance scale. On the left, a sealed jar with ice cubes weighs 200g. On the right, the same jar with melted water also weighs 200g, showing the scale is perfectly balanced.

Have you ever wondered if a glass of ice weighs less after it melts into water? 🧊 ➡️ 💧 The answer is a big scientific NO!

⚖️ The Golden Rule: Law of Conservation of Mass

This is one of the most important rules in the universe. It states that matter cannot be created or destroyed; it only changes form.

Think of the particles (atoms and molecules) like students in a classroom. Whether they are sitting at their desks (Solid), walking around (Liquid), or running at recess (Gas), the number of students stays the same. None of them disappear!

🧱 The LEGO® Analogy

Imagine building a castle with 100 LEGO bricks. If you take the castle apart and put the bricks in a pile, do you have fewer bricks? No! You still have 100 bricks. The shape changed, but the mass (amount of stuff) remained the same.

🧪 The Sealed Jar Experiment

If you put an ice cube in a jar, seal the lid tight, and weigh it, let's say it's 200 grams. After the ice melts completely, if you weigh it again, it will still be exactly 200 grams. The water didn't escape!

Tracking the Mass

State of Matter	What Happens?	Mass (Weight)
🧊 Solid (Ice)	Particles vibrate in place	100 grams
💧 Liquid (Water)	Particles slide past each other	100 grams
💨 Gas (Steam)	Particles fly far apart*	100 grams

*Note: For gas, you must catch all the steam in a balloon or jar to prove the weight is the same!

Key Facts

⚖️ Mass stays the same during phase changes (melting, freezing, boiling).

⚛️ Particles are not destroyed; they just change how they move.

🎈 To measure gas mass correctly, you must use a closed container.

7 Key Vocabulary

Master these important terms for your exam:

Term	Definition
Matter Materia	Anything that has mass and takes up space. Cualquier cosa que tiene masa y ocupa espacio.
Solid Sólido	A state of matter with a fixed shape and volume; particles vibrate in place. Un estado de la materia con forma y volumen definidos; las partículas vibran en su lugar.
Liquid Líquido	A state of matter with a fixed volume but no fixed shape; it takes the shape of its container. Un estado de la materia con volumen definido pero sin forma fija; toma la forma de su recipiente.
Gas Gas	A state of matter with no fixed shape or volume; particles move freely and quickly. Un estado de la materia sin forma ni volumen definidos; las partículas se mueven libre y rápidamente.
Particle Partícula	A very small piece of matter that makes up everything around us. Una pieza muy pequeña de materia que compone todo lo que nos rodea.
Kinetic Energy Energía Cinética	The energy an object has due to its motion. La energía que tiene un objeto debido a su movimiento.
Thermal Energy Energía Térmica	The total energy of the moving particles in an object (heat energy). La energía total de las partículas en movimiento dentro de un objeto (energía calorífica).
Temperature Temperatura	A measure of the average kinetic energy of the particles in a substance. Una medida de la energía cinética promedio de las partículas en una sustancia.
Melting Fusión	The change of state from a solid to a liquid. El cambio de estado de sólido a líquido.
Freezing Solidificación	The change of state from a liquid to a solid. El cambio de estado de líquido a sólido.
Evaporation Evaporación	The process where a liquid turns into a gas at the surface of the liquid. El proceso donde un líquido se convierte en gas en la superficie del líquido.
Boiling Ebullición	The process where a liquid turns into a gas throughout the liquid, creating bubbles. El proceso donde un líquido se convierte en gas en todo el líquido, creando burbujas.
Condensation Condensación	The change of state from a gas to a liquid. El cambio de estado de gas a líquido.
Sublimation Sublimación	The change of state directly from a solid to a gas without becoming a liquid first. El cambio de estado directamente de sólido a gas sin pasar primero por líquido.
Deposition Deposición	The change of state directly from a gas to a solid without becoming a liquid first. El cambio de estado directamente de gas a sólido sin pasar primero por líquido.
Melting Point Punto de Fusión	The specific temperature at which a solid becomes a liquid. La temperatura específica a la cual un sólido se convierte en líquido.
Boiling Point Punto de Ebullición	The specific temperature at which a liquid becomes a gas. La temperatura específica a la cual un líquido se convierte en gas.

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