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Boyle’s Law What are the 4 variables that describe a gas phase system? • • • • Volume Temperature Pressure Amount of gas (in moles) Fixed Mass? • You don’t change the number of moles of gas. That is… BOYLE - 1662 Temperature and Amount are constant. Look at relationship between P and V. What happened when I increased the pressure on the syringe? As pressure increases, volume decreases. Image From Tiger Boyle’s Law: 4 step J-Tube experiments Pressure (atm) Volume (cm3) 1 1.00 800 2 2.00 400 3 3.00 267 4 4.00 200 Trial Inverse Relationships • Graph of two variables is a ... • Properties: – Relationship is inverse. – Product of the two variables is a constant. Scientists plot data because a picture shows relationships better than lists of numbers. There are lots of “pictures” that scientists & mathematicians recognize. Trial Pressure (atm) Volume (cm3) Pressureď‚·Volume (atm-cm3) 1 1.00 800 800 2 2.00 400 800 3 3.00 267 800 4 4.00 200 800 For a given T and amount, pressure X volume always equals the same number – the product is CONSTANT! Comparison Pressure Change Volume Change Trials 1 & 2 1 to 2 800 to 400 2 to 1 Trials 1 & 3 1 to 3 800 to 267 3 to 1 Trials 1 & 4 1 to 4 800 to 200 4 to 1 Boyle’s Law - words • The volume of a sample of gas is inversely proportional to its pressure, at constant temperature. Boyle’s Law - mathematically P x V = k (constant) V = k/P or P = k/V P1V1 = P2V2 For every point on the hyperbola, P x V = the same constant, k