Key Summary & High-Yield Concept Takeaways
Curated by senior faculty at Hodu Academy for fast revision, formula derivations, and standard board & competitive exam marking schemes.
- ✓P = Pressure of the gas
- ✓V = Volume of the gas
- ✓k = Constant (for fixed mass and temperature)
- ✓Syringe: Pressing the plunger decreases volume, increases pressure, and injects fluid.
Boyle’s Law – Definition, Formula & Real-Life Examples
Boyle’s Law explains how the pressure and volume of a gas are related. From medical syringes to bicycle pumps, this fundamental law is at work around us every day. Let’s explore its definition, formula, applications, and solve some problems!
Definition of Boyle’s Law
Boyle’s Law states that the pressure of a given mass of gas is inversely proportional to its volume, provided the temperature remains constant.
P ∝ 1/V or PV = k
Where:
- P = Pressure of the gas
- V = Volume of the gas
- k = Constant (for fixed mass and temperature)
Mathematical Formula (Boyle’s Law Equation)
If a gas changes from an initial state (P₁, V₁) to a final state (P₂, V₂), Boyle’s Law gives:
P₁V₁ = P₂V₂
Real-Life Examples of Boyle’s Law
- Syringe: Pressing the plunger decreases volume, increases pressure, and injects fluid.
- Human lungs: Inhalation expands lung volume (lowering pressure, air enters); exhalation contracts lungs (raising pressure, air exits).
- Bicycle pump: Pushing the handle compresses air, increasing pressure to inflate tires.
- Air bubbles underwater: As bubbles rise and water pressure drops, their volume increases.
- Spray cans: Pushing the nozzle reduces volume, increasing pressure to force paint out.
Practice Problems
- A balloon contains hydrogen at 3.45 L and 1 bar. What volume will it occupy at 1.3 bar?
- Gas in a 150 mL vessel at 1.5 bar is moved to a 200 mL vessel. What is the new pressure?
- 20 L of gas at 37 mm Hg is compressed to 50 mm Hg. What is the final volume?
- How much pressure is needed to compress 400 ft³ of gas into a 3 ft³ tank?
FAQs on Boyle’s Law
- When does Boyle’s law apply? – In isothermal processes (constant temperature for a fixed amount of gas).
- Is Boyle’s law valid for liquids? – No, because liquids are nearly incompressible.
- Why does Boyle’s law fail at high pressure? – Real gases deviate from ideal behavior at high pressure/low temperature.
- How does Boyle’s law work? – Pressure and volume of a gas are inversely related at constant temperature: decrease one, the other increases.
Summary
Boyle’s Law is a core principle in gas physics and chemistry. It reveals how gases respond to changes in pressure and volume at constant temperature—vital for understanding breathing, syringes, pumps, and more. Practice problems and real-world examples make it easy to master!
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