Boyle’s Law is one of the cornerstones of gas laws in chemistry and physics. It defines how pressure and volume are inversely related in a confined gas when temperature and mass remain constant. Whether you’re a student, a teacher, or someone preparing for exams like NEET, JEE, or SAT, mastering Boyle's Law with a real-world perspective will simplify many complex problems.
What Is Boyle’s Law?
Boyle’s Law states that the pressure of a gas increases as its volume decreases, provided the temperature and the number of gas particles remain unchanged. Mathematically, it is written as:
P ∝ 1/V or P × V = constant
Here:
- P is the pressure of the gas,
- V is the volume of the gas,
- The product of pressure and volume remains constant when temperature is constant.
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Historical Insight: Who Gave Boyle’s Law?
This principle was first established by Robert Boyle, an Anglo-Irish scientist, in 1662. His experiments were among the first reliable scientific measurements on gases. By observing how a fixed amount of gas behaved under varying pressure, he concluded that the volume of a gas decreases proportionally as pressure increases — laying the foundation for Boyle’s Law.
Real-Life Analogy and Diagram
Imagine a syringe:
- When you pull the plunger, you increase the volume inside, so the pressure drops.
- When you push it down, volume decreases, so pressure increases.
This exact behavior is depicted in the infographic where:
- Pulling u
- own compresses the gas, increasing pressure.
Mathematical Explanation of Boyle’s Law
At constant temperature (T) and number of moles (n):
Where:
- k1 is a proportionality constant.
- The constant depends on the amount of gas, temperature, and unit system used.
When comparing two states of the same gas:
Boyle’s Law in Action: What Happens When Volume Is Halved?
Let’s say:
- You start with volume V and pressure P.
- If you reduce the volume to ½V, the pressure becomes 2P.
This is because:
Result: The pressure doubles.
Physics Formulas for Class 11 and Class 12
Applications of Boyle’s Law in Daily Life
- Scuba Diving: As divers descend, pressure increases and the volume of air in their lungs or tanks decreases.
- Syringes and Pumps: Medical syringes and bicycle pumps use Boyle’s law principles.
- Breathing: Our lungs operate on this principle. When we inhale, lung volume increases, causing pressure to drop and air to flow in.
- Vacuum Packing: Removing air (decreasing pressure) reduces volume, preserving food longer.
- Airplane Cabin Pressurization: Boyle’s Law helps engineers regulate air pressure in cabins at high altitudes.
Boyle’s Law vs Charles’ Law vs Gay-Lussac’s Law
| Law | Variable Kept Constant | Relationship | Formula |
|---|---|---|---|
| Boyle’s Law | Temperature | P ∝ 1/V | P × V = constant |
| Charles’ Law | Pressure | V ∝ T | V/T = constant |
| Gay-Lussac’s Law | Volume | P ∝ T | P/T = constant |
FAQs about Boyle’s Law
What is Boyle’s Law in simple terms?
Boyle’s Law says that when the volume of a gas decreases, its pressure increases, as long as the temperature and gas amount are constant.
How is Boyle’s Law used in breathing?
When you breathe in, your chest expands, increasing lung volume and reducing pressure, causing air to rush in.
What happens to pressure if volume triples?
If volume increases to 3V, pressure will become 1/3rd of the original pressure, assuming temperature is constant.
Is Boyle’s Law valid for all gases?
It applies best to ideal gases, but real gases also obey Boyle's Law under low pressure and high temperature conditions.
Can Boyle’s Law be used in vacuum technology?
Yes, it is crucial in vacuum systems where changes in volume affect pressure significantly.
