Phase Changes

Front

Phases Noun

---

[fey-ziz]

Back

Phases

---

The distinct states of a substance, such as solid, liquid, or gas, that coexist as physically separate parts of a mixture.

---

Example: This diagram shows the three common phases of matter—solid, liquid, and gas—and how adding or removing heat energy causes them to change state.

Front

Endothermic process Noun

---

[en-doh-thur-mik pros-es]

Back

Endothermic process

---

A physical or chemical process that absorbs thermal energy from its surroundings, causing the surroundings to cool down.

---

Example: Applying heat to liquid water gives it energy, causing it to boil and change into a gas (vapor). This process absorbs heat, making it endothermic.

Front

Melting Noun

---

[mel-ting]

Back

Melting

---

The endothermic phase transition process by which a substance changes from a solid state to a liquid state.

---

Example: This image shows that melting is the process where a substance changes from a solid state, like an ice cube, to a liquid state, like a puddle of water.

Front

Heat Noun

---

[heet]

Back

Heat

---

The transfer of thermal energy from an object at a higher temperature to an object at a lower temperature.

---

Example: This diagram shows that heat is energy that flows from a hot object to a cold object, a process that can cause phase changes.

Front

Melting point Noun

---

[mel-ting point]

Back

Melting point

---

The specific temperature at which a crystalline solid breaks its lattice structure and transforms into a liquid.

---

Example: This image shows a solid substance being heated until it turns into a liquid. The thermometer measures the exact temperature at which this phase change occurs, which is the melting point.

Front

Vaporization Noun

---

[vey-per-uh-zey-shuhn]

Back

Vaporization

---

The endothermic phase transition process by which a substance in a liquid state changes to a gaseous state.

---

Example: The image shows the two types of vaporization. Evaporation happens at the liquid's surface without bubbles, while boiling happens throughout the liquid with bubbles.

Front

Vapor Noun

---

[vey-per]

Back

Vapor

---

The gaseous phase of a substance that is typically a liquid or solid at standard room temperature and pressure.

---

Example: This diagram shows that vapor is the gas state of matter, like steam. It is formed when a liquid, like water, heats up and undergoes evaporation.

Front

Evaporation Noun

---

[ih-vap-uh-rey-shuhn]

Back

Evaporation

---

A type of vaporization where a liquid turns into a gas, occurring specifically at the surface of the liquid.

---

Example: Energy from the sun heats liquid water in the ocean, causing it to turn into a gas (water vapor) and rise into the atmosphere.

Front

Vapor pressure Noun

---

[vey-per presh-er]

Back

Vapor pressure

---

The pressure exerted by the vapor of a substance in equilibrium with its condensed phases in a closed system.

---

Example: This diagram shows how liquid molecules escape into a closed space, becoming a vapor that creates a measurable force called vapor pressure.

Front

Boiling point Noun

---

[boi-ling point]

Back

Boiling point

---

The temperature at which a liquid's vapor pressure equals the external pressure, causing the liquid to turn into vapor.

---

Example: This image shows water in a pot being heated until it boils, turning into steam. A thermometer indicates this phase change happens at a specific temperature: 100°C.