Gas Class #4 OB: continued investigation into gases, and gas chemistry Demo diagram #2 today, to add to the first one (hot and cold balloons)

Demo Diagram #2: Balloon in the Bell Jar Start conditions: normal air pressure with balloon of “normal” size. Conditions will change: pressure drops inside the bell jar, what will happen to balloon volume? Turn on the machine and watch. Start conditions

Demo Diagram #2: Balloon in the Bell Jar Start conditions: normal air pressure with balloon of “normal” size. Conditions will change: pressure drops inside the bell jar, what will happen to balloon volume? As pressure drops, volume increases. Pressure + Volume are Inversely Proportional. Start conditions Pressure in the bell decreases, balloon grows

Pressure as function of Volume of a gas P volume Demo Diagram #2 Pressure and Volume Pressure and volume are inversely proportional. As one variable increases, the other decreases. In the combined gas law, Pressure and Volume are multiplied across the top of the formula. Boyle’s Law states: P 1 V 1 = P 2 V 2 Also… Pressure x Volume = a gas constant for the sample

44 Questions, 27. When the average kinetic energy of a gaseous system is increased, the average molecular velocity of the system A. increases and the molecular mass increases B. increases and the molecular mass remains the same C. decreases and the molecular mass increases D. decreases and the molecular mass remains the same

44 Questions, 27. When the average kinetic energy of a gaseous system is increased, the average molecular velocity of the system A. increases and the molecular mass increases B. increases and the molecular mass remains the same C. decreases and the molecular mass increases D. decreases and the molecular mass remains the same

44 Questions, 28. The volume of a given mass of an ideal gas at constant pressure is A. inversely proportional to Celsius Temp B. inversely proportional to Kelvin Temp C. directly proportional to Celsius Temp D. directly proportional to Kelvin Temp 29. A gas at STP has a volume of 1.0 liters. If the pressure is doubled and the temperature remains constant, the new volume of the gas will be A. 4.0 L B L C L D. 2.0 L

44 Questions, 28. The volume of a given mass of an ideal gas at constant pressure is A. inversely proportional to Celsius Temp B. inversely proportional to Kelvin Temp C. directly proportional to Celsius Temp D. directly proportional to Kelvin Temp 29. A gas at STP has a volume of 1.0 liters. If the pressure is doubled and the temperature remains constant, the new volume of the gas will be P 1 V 1 = P 2 V 2 (1 atm)(1.0 L) = (2 atm)(V 2 ) 0.50 L = V 2 A. 4.0 L B L C L D. 2.0 L

30. As the pressure on a given sample of gas increases at constant temperature, the mass of the sample of gas A. increases B. decreases C. remains the same

Matter cannot be created nor destroyed…

31. Explain in terms of the Kinetic Molecular Theory of gases, the increase in pressure of a sample of gas when the gas is heated from 273 Kelvin to 298 Kelvin.

31. Explain in terms of the Kinetic Molecular Theory of gases, the increase in pressure of a sample of gas when the gas is heated from 273 Kelvin to 298 Kelvin. An increase in temperature is also an increase in kinetic energy. As kinetic energy increases, so do the number of collisions, and the strength of the collisions also increases. Any increase in collisions or strength of collisions results in higher pressure. Collisions cause gas pressure.

M ???

32. A sample of gas A was stored in a container at 50°C and 0.50 atm. Gas B is stored at STP. Compared to a gas B, gas A has A. lower temp and higher pressure B. lower temp and lower pressure C. higher temp and lower pressure D. higher temp and higher pressure

MAKE A CHART AND LOOK, stay out of your head GAS AGAS B 323 Kelvin273 Kelvin 0.50 atm1.0 atm

34. The average kinetic energy of the molecules of an ideal gas is directly proportional to A. pressure at standard temp B. volume occupied by the individual gas molecules C. temperature in Kelvin D. number of moles of gas present

34. The average kinetic energy of the molecules of an ideal gas is directly proportional to A. pressure at standard temp B. volume occupied by the individual gas molecules C. temperature in Kelvin D. number of moles of gas present

35. Which change must result in an increase in the average kinetic energy of the molecules of a given sample of nitrogen gas? A. temperature change from 20°C → 30°C B. pressure change from 0.50 → 1.0 atm C. temperature change from 355 K → 299 K D. volume change from 1.0 → 2.0 liters

35. Which change must result in an increase in the average kinetic energy of the molecules of a given sample of nitrogen gas? A. temperature change from 20°C → 30°C This requires an increase in temperature. This is NOT a calculation, you need an increase in temperature even if it’s in Centigrade. Kelvin is for the math, this is just getting hotter