[Leejohnston]

## The Ideal Gas Law — Why Gases Expand

### 1. The Equation

PV = nRT

---

### 2. What Each Symbol Means

- P = pressure
- V = volume
- n = number of moles
- R = gas constant
- T = temperature (kelvin)

---

### 3. What the Equation Is Telling Us

Pressure, volume, and temperature are linked.

Changing one forces the others to respond.

---

### 4. Where It Comes From (Intuition)

Gas particles are in constant motion.

Heating them increases motion → more collisions → higher pressure.

---

### 5. Worked Example

If temperature increases while volume stays fixed:
- pressure must rise

This is why sealed containers can burst when heated.

---

### 6. Real-World Applications

- Weather balloons
- Engines
- Refrigeration
- Atmospheric science

---

### 7. Common Misconceptions

- Gases expand because they “want to” → false
- Temperature is heat → false
- Pressure and force are the same → false

---

### Try It Yourself

Why do hot air balloons rise?