Study guide: Changes of State

📋 Course Outline

1. Changes Between States
2. Boiling and Evaporation
3. Condensation and Dry Ice

📖 1. Changes Between States

🔑 Key Concepts & Definitions

• Vaporization: The change of state from a liquid into a gas, such as when liquid water becomes steam.

★ Must-know

📌 When a liquid is cooled below 0°C, it freezes and changes into a solid.

• The changes of state are:
  • melting from solid to liquid
  • boiling or evaporation from liquid to gas
  • condensation from gas to liquid
  • freezing from liquid to solid
  • sublimation from solid to gas
  • deposition from gas to solid

Further detail

• Salt melts at 804 and freezes at 804.

💡 Memory Hook

Solid → liquid → gas: melting, then boiling or evaporation; reverse with condensation, freezing, and deposition.

📖 2. Boiling and Evaporation

★ Must-know

📌 Evaporation can happen at any temperature, whereas boiling happens at 100°C.

📌 At higher altitudes, water boils at less than 100°C because the air is thinner and the air pressure is lower.

Further detail

📌 Steam is visible, whereas water vapour is invisible.

💡 Memory Hook

Evaporation can occur at any temperature, whereas boiling occurs at 100°C.

📖 3. Condensation and Dry Ice

★ Must-know

• When a cold drink is placed outside, water vapour from the air cools and turns into liquid water on the drink.

Further detail

• Dry ice can harm humans by causing frostbite and body tissue damage.

💡 Memory Hook

Cold drink → water vapour cools → liquid water appears.

📊 Synthesis Tables

Evaporation and Boiling