Gases Unit 3 PDF

Unit 3: Gases Empirical (Observable) Proper ties Take shape of container – No definite volume or shape Hold a lot of Ek – Molecules are moving quickly Can be compressed – Large spaces between molecules Fluid – Can flow  Unable to see because of space between particles – U...

Unit 3: Gases Empirical (Observable) Proper ties Take shape of container – No definite volume or shape Hold a lot of Ek – Molecules are moving quickly Can be compressed – Large spaces between molecules Fluid – Can flow  Unable to see because of space between particles – Use quantitative properties to characterize Pressure (P) Volume (V) # particles (moles) Temperature (T) – These properties can be manipulated Manipulate one  effect on another  You have 5 gas cylinders; all have the same mass of N2(g) What is the order of gas cylinders, from most likely to explode to least likely to explode? Relationship between Pressure & Volume Temperature & amount (moles) remain constant Pressure – Force over an area P=F/A If F , P ? F , P   Units of Pressure – Millimeters of mercury mm Hg – Pascal (Pa) kPa =1000 Pa – Atmosphere atm  Standard Pressures – @ sea level =1 atm = 760 mm Hg = 101.325 kPa *101 kPa *Higher up you go, the lower the pressure  Pressure Ratios 1 atm 101 kPa 1 atm 760 mm Hg 101 kPa 760 mm Hg  To covert: – Multiply given pressure by a conversion factor! 101 1 atm kPa 101 kPa 1 atm  Pressure Conversions: kPA atm mm Hg 96.5 825 2.50  Pressure Conversions: kPA atm mm Hg 96.5 0.955 726 110 1.09 825 253 2.50 1.90 x 103 (1900)  Standard conditions – STP Standard temperature & pressure 101 kPa – SATP Standard ambient temperature & pressure 100 kPa Lab Assignment 1: Pressure, Volume & Temperature go-el.com – Boyle’s & Charles’ Law Part A: Relationship between Pressure & Volume – Problem – Hypothesis – Data – Analysis Graph – X-axis = manipulated variable – Y-axis = responding variable –  What is the relationship between pressure & volume? – As P , V  – As P , V  BOYLE’S LAW – As P , V  proportionally If P  x2, V  x2 – T & amount (moles) – Units Pressure = kPa Volume = L  P1V1 = P2V2 – Rearranging the equation: At an initial pressure, a gas has a particular volume. What would the volume be if the pressure was changed? V2 = P1V1 P2 – Example: A 2.0L party balloon at 98 kPa is taken to the top of a mountain where the pressure is 75 kPa. Assume that the temperature and chemical amount of the gas remain the same. What is the new volume of the balloon? V2 = (98kPa) P1V 1 = P 2V 2 (2.0L) 75kPa V 2 = P 1V 1 V2 = 2.6L G S I D R! P2 I G TE S T M A  Workbook – Boyle’s Law #1-7 Lab Assignment 1: Pressure, Volume & Temperature https://gizmos.explorelearning.com/ – Boyle’s & Charles’ Law Part B: Relationship between Temperature & Volume – Problem – Hypothesis – Data – Analysis Graph – X-axis = manipulated variable – Y-axis = responding variable – Relationship between Temperature & Volume Amount (moles) & pressure are constant Place a balloon into liquid N2 (-196°C) – What happens? Why? T , V  T , V   Temperature Scales – Celsius scale Based on properties of water 0ºC – freeze/melt 100ºC – condense/evaporate – Kelvin scale Based on absolute zero – No Ek (motion) – Theoretically, V = 0 @  °C  K +273 K  °C -273 Convert the following Celsius temperatures to absolute temperatures. a) OºC c) -30ºC b) 100ºC d) 25ºC Convert the following absolute temperatures to Celsius temperatures. a) 0K c) 300K b) 100K d) 373K  Charles’ Law – As T , V  proportionally – P & amount (moles) are constant V1 = V2 T1 T2 Units: Volume = L Temperature = K – Rearranging the equation: What is the new volume of a gas if it’s temperature was decrease from it’s initial temperature? V1 = V2 V1T2 = V2T1 T1 T2 S! I T R UN V2 = V1T2 O U K Y T1 E C CH – Example: In a test of Charles’ Law, a gas inside a cylinder with a movable piston is heated to 315ºC. The initial volume of gas in the cylinder is 0.30L at 25ºC. What will be the final volume when the temperature is 315ºC? V1T2 = V2T1 V1 = V2 T1 T2 V2 = (0.30L)(588K) (298K) V2 = V1T2 V2 = 0.59L T1 ONLY 2 SIG DIGS – you didn’t use  Workbook – Charles’ Law #1-7  Relationship between Temperature & Pressure If P , T If P , T Proportional – Shows relationship between P, V & T Amount (moles) remains constant – The relationship P x V is constant @ fixed T – The relationship V / T is constant @ fixed P  P1V1 = P2V2 T1 P1V1 = P1V1 = T2 P2V2 P2V2 T1BOYLE’S TCHARLES’ 1 T2 LAW T2 LAW Can be simplified to either law Pressure = kPA Volume = L T must be in K! – The pressure in an automobile tire is 200kPa at 27ºC. At the end of the journey on a hot sunny day the pressure has risen to 223kPa. What is the temperature of the air in the tire? (Assume V has not changed). P1T2 = P2T1 P1V1 = P2V2 T1 T2 T2 = P2T1 P1 T2 = (223kPa)(300K) 200kPa ALLOWED 3 SIG DIGS – you didn’t T2 = 334.5 K use 27ºC directly! T = 61.5 ºC  Workbook – Combined Gas Law #1-8  Imploding Can – What is the difference between an implosion and an explosion? – Let’s do it! – Can you explain why the can imploded? Use the ideas of temperature, volume and pressure in your explanation.