Transcript 250_gaslaws
GAS LAWS-FOR CLOSED SYSTEMS LAW OF CHARLES = CAUSES PV1 T1 INCREASE AVERAGE KINETIC ENERGY(T) PV2 T2 TEMP IS IN KELVIN P1V1 T1 = P2V2 T2 TEMP IS IN KELVIN INCREASE OF MOMENTUM K = C + 273 K = C + 273 CAUSES CAUSES INCREASED VOLUME IN AN EXPANDABLE (CONSTANT PRESSURE) CONTAINER LAW OF GAYLUSSAC INCREASE COLLISION CAUSES FREQUENCY INCREASED PRESSURE IN A RIGID (CONSTANT VOLUME) CONTAINER GAS LAWS INCREASE EXTERNAL PRESSURE LAW OF BOYLE CAUSES P1V1 T = P2V2 T TEMP IS IN KELVIN INCREASE OF EXTERNAL COLLISIONS K = C + 273 CAUSES EXPANDABLE CONTAINER PUSHED INTO SMALLER V CAUSES DECREASED VOLUME IN AN EXPANDABLE CONTAINER AT CONSTANT TEMPERATURE • THE LAWS OF GAY-LUSSAC (P and V) And the law of Charles (V and T) ARE DIRECT PROPORTIONS – AS ONE INCREASES THE OTHER INCREASES DIRECTLY. BOYLES LAW IS AN INVERSE PROPORTION, AS P INCREASES, VOLUME DECREASES. PV=k • P V PROBLEM SOLVING, GAS LAWS • STEP ONE: ANALYZE. Read the problem an set up your givens. • STEP TWO: CHECK UNITS, CONVERT NOW SO YOU DO NOT FORGET ! • STEP THREE: CRITICAL THINKING THE LOGIC! – DECIDE WHAT IS CONSTANT AND WHAT IS CHANGING, THEN DECIDE WHAT LAW TO APPLY. • STEP FOUR: MAKE A LOGICAL ESTIMATION BASED ON THE APPROPRIATE GAS LAW, THEN USE THE EQUATION. • STEP FIVE, CHECK, SUBSTITUTE IN YOUR ANSWER TO SEE IF THE EQUATION CORRECTLY SOLVES FOR A GIVEN. EXAMPLE. CALCULATE THE VOLUME OF A 1.0L BALLOON THAT IS PRESSURIZED FROM 1.0 ATM TO 2.0 ATM AT CONSTANT TEMP. • STEP ONE: ANALYZE. Read the problem an set up your givens. – – – – P#1 = 1.0ATM P#2 = 2.0ATM V#1 = 1.0L V#2 = X LOGIC – PRESSURE AND VOLUME CHANGE,AT CONSTANT TEMP, THEREFORE THIS IS BOYLE’S LAW – WHICH IS AN INVERSE PROPORTION. – AT CONSTANT TEMPERATURE • • STEP TWO:CHECK UNITS – NET NEEDED HERE! STEP THREE: CRITICAL THINKING THE LOGIC! – DECIDE WHAT IS CONSTANT AND WHAT IS CHANGING, THEN DECIDE WHAT LAW TO APPLY. – – P#1 = 1.0ATM P#2 = 2.0ATM – V#1 = 1.0L – V#2 = X PRESSURE IS INCREASING (DOUBLES), THEREFORE VOLUME WILL DECREASE VOLUME WILL DECREAS (HALVED), BECAUSE PRESSURE DOUBLED. • STEP FOUR: MAKE A LOGICAL ESTIMATION BASED ON THE APPROPRIATE GAS LAW, THEN USE THE EQUATION. – -BECAUSE PRESSURE DOUBLES, THE VOLUME WILL DECREASE (IVERSELY PROPORTIONAL CHANGE). As the initial volume is 1.0 L the final volume should be 0.50 L • • P1V1 T1 • CHECK (FOR MATH ERRORS, THIS WILL NOT FIND LIGICAL ERRORS AT ALL TIMES.) = P2V2 T2 (1.0 atm)(1.0 L) = (2.0 atm)( X) X= 0.50L – P1V1 = P2V2 (1.0 ATM)(1.0L) = (2.0 ATM)(0.50L)