Behavior of Gases (Gas Law)

• Most essential learning competencies

  • Investigate the relationship between the volume and pressure at constant temperature of gas
  • Investigate the relationship between the volume and temperature at constant pressure of a gas
• Boyle's law


  The volume of a fixed amount of gas is inversely proportional to its pressure at constant temperature
• Boyle's experiment


  1. Trapped a fixed amount of air in a J-tube

  2. Changed the pressure and observed the effect on the volume

  3. Concluded that volume is inversely proportional to pressure at constant temperature
• The volume decreases as the pressure is increased and if the pressure is decreased the volume increases
• Boyle's law experiment setup

  1. Syringe

  2. Glue gun

  3. Glue sticks

  4. Weights or books

  5. Stand holder

  6. Activity sheet
• The initial reading for the volume of gas is 12 ml, the mass is 0 grams and pressure is 0 newton per meter squared
• Boyle's law experiment steps

  1. Fill syringe with air

  2. Seal opening with glue

  3. Create weight holder

  4. Carefully place weights

  5. Record volume, mass and compute pressure
• As the number of books increased

  The volume of gas inside the syringe decreases while the pressure increases
• Boyle's law


  At constant temperature and amount of air, as the pressure increases the volume decreases, and if the pressure decreases the volume increases
• A hand bicycle pump works similar to a syringe, when the handle is pushed down the pressure inside increases and the gas is compressed
• Relationship between volume and pressure of gases at constant temperature

  Inversely proportional
• Charles law


  The volume of a fixed amount of gas is directly proportional to the kelvin temperature at constant pressure
• Charles law experiment setup

  1. Inflated balloon

  2. Tape measure

  3. Thermometer

  4. Iced water

  5. Hot water

  6. Tap water

  7. Activity sheet
• When the balloon is placed in hot water, it expands and the volume increases. When placed in iced water, it contracts and the volume decreases.
• Sample problem on Charles law

  Given: Initial volume 0.75 liters at 30 degrees Celsius, Final temperature -10 degrees Celsius. Find the final volume if pressure remains constant.
• Solving Charles law problem

  1. Identify the given: v1=0.75 liters, t1=303 Kelvin, t2=263 Kelvin, solve for v2

  2. Substitute in Charles law formula: v1/t1 = v2/t2

  3. Multiply both sides by t2, solve for v2

  4. v2 = 0.65 liters