Know the melting and boiling temperatures for water at standard atmospheric pressure

2.2.3 Melting, boiling and evaporation

Key temperatures for water (standard atmospheric pressure)

Why these temperatures matter

• The melting point tells us when ice turns into water – a simple way to understand phase change.

• The boiling point shows the temperature at which water starts to vaporise, which is crucial for cooking, steam engines and weather patterns.

• Knowing these values helps predict how water behaves in everyday life and in experiments.

Analogy 1: Ice cube to water 🌊

Imagine a chocolate bar that melts at room temperature. When you leave it on a warm table, the solid chocolate slowly turns into a liquid. That’s exactly what happens to ice at \$0^\circ\text{C}\$ – the solid water (ice) absorbs heat and becomes liquid water. The energy absorbed is called latent heat of fusion and it’s like the chocolate needing extra “warmth” to change state.

Analogy 2: Boiling kettle ☕️

Think of a kettle on the stove. As the heat increases, the water inside starts to bubble. When the temperature reaches \$100^\circ\text{C}\$, the bubbles grow larger and the water turns into steam. This is the latent heat of vaporisation – the energy required for water molecules to escape into the air.

Quick quiz

1. What is the melting point of water? 🌡️
2. At what temperature does water boil at standard pressure? 🔥
3. Why does ice melt at \$0^\circ\text{C}\$ even though it feels cold? ❄️

Key take‑aways

• Melting point of water: \$0^\circ\text{C}\$.
• Boiling point of water: \$100^\circ\text{C}\$.
• Both temperatures are measured at standard atmospheric pressure (1 atm).
• These values are constants that help us predict water’s behaviour in science and daily life.