1 Gases (Vapors) Gases expand to fill any container. Therefore, gases are highly compressible.

2 Kinetic Molecular Theory (of an Ideal Gas): 1. Gases are composed of molecules or atoms whose size is negligible compared to the average distance between them. (Most of the space in the gas container is empty.) 2. Gas molecules move randomly in straight lines in all directions at various speeds. 3. The forces of attraction or repulsion between gas molecules are very weak or negligible (except during collisions) 4. Collisions between gas molecules are considered elastic. 5. The average kinetic energy of a molecule is proportional to the absolute temperature.

3 molecules of air Where is the pressure the greatest? We live in “sea of air” Why does a diver get the bends?

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4 VARIABLES THAT CAN BE ALTERED IN A GAS: 1. AMOUNT OF A GAS 2. VOLUME OF A GAS 3. TEMPERATURE OF A GAS 4. PRESSURE OF A GAS

STP - Standard Temperature and Pressure Standard Temperature is 0°C All temperature calculations in a gas must be in Kelvin (K). Reminder: K = C° + 273

Standard Pressure is 1 atmosphere (atm) at sea-level Helpful Hint: There is more than one type of pressure unit. Here is the conversion factor. 1 atm = 760 mmHg = 101 kPa

A way to describe the characteristics of a gas as conditions change. For each gas law certain variables (amount, temp., pressure, volume) change while others are assumed to remain constant.

Robert Boyle investigated the relationship between the volume of a gas and its pressure. The other two variables, amount and temperature, were assumed to be constant (unchanged).

11 Pressure and Volume: Boyle’s Law How is the pressure applied to a gas related to its volume? Piston Gas molecules Let’s apply pressure

12 Pressure and Volume: Boyle’s Law How is the pressure applied to a gas related to its volume? Piston Gas molecules Piston Gas molecules Boyle’s Law: P 1 V 1 = P 2 V 2 Volume is inversely proportional to applied pressure.

13 The Harder we Push the smaller the gas volume gets! Boyle’s Law: P 1 V 1 = P 2 V 2

Boyle’s Results: 1. As pressure increases, volume decreases. 2. As pressure decreases, volume increases. 3. The volume of a fixed amount of gas varies inversely with the pressure of the gas.

Boyles Law Equation: P 1 V 1 = P 2 V 2

SAMPLE BOYLE’S LAW PROBLEM: A sample of gas has a volume of 2.5 liters at a pressure of 800 mmHg. What is the volume when the pressure drops to 500 mmHg? A sample of gas has a volume of 2.5 liters (V 1 ) at a pressure of 800 mmHg (P 1 ). What is the volume (V 2 ) when the pressure drops to 500 mmHg (P 2 )?

P 1 V 1 = P 2 V 2 IDENTIFY THE EQUATION YOU WILL USE: PLUG IN YOUR NUMBERS FROM THE QUESTION: (800 mmHg)(2.5L) = (500 mmHg)(V 2 ) SOLVE: V 2 = 4L

The volume of the lungs is measured by the volume of air inhaled or exhaled. If the volume of the lungs is L during exhalation and the pressure is KPa, and the pressure during inhalation is KPa, what is the volume of the lungs during inhalation?

The total volume of a soda can is 415 mL Of this 415 mL, there is 60.0 mL of headspace for the CO 2 gas put in to carbonate the beverage. If a volume of mL of gas at standard pressure is added to the can, what is the pressure in the can when it has been sealed?

It is hard to begin inflating a balloon. A pressure of KPa is required to initially inflate the balloon mL. What is the final pressure when the balloon has reached it's capacity of 1.2 L?

If a piston compresses the air in the cylinder to 1/8 it's total volume and the volume is 930 cm 3 at STP, what is the pressure after the gas is compressed?

If a scuba tank that has a capacity of 10.0 dm 3 is filled with air to KPa, what will be the volume of the air at KPa?

23 Temperature and Volume: Charles’s Law How is the volume of a gas related to its temperature? gas molecules moveable mass (constant pressure) What happens if heat is applied to the gas?

24 Temperature and Volume: Charles’s Law How is the volume of a gas related to its temperature? gas molecules moveable mass (constant pressure) Why did the volume change? What happens to the average speed of the gas molecules?.

25 Temperature and Volume: Charles’s Law How is the volume of a gas related to its temperature? gas molecules moveable mass (constant pressure) Why did the volume change? What happens to the average speed of the gas molecules?.

If I have 45 liters of helium in a balloon at 25 0 C and increase the temperature of the balloon to 55 0 C, what will the new volume of the balloon be?

Calcium carbonate decomposes at C to form carbon dioxide and calcium oxide. If 25 liters of carbon dioxide are collected at C, what will the volume of this gas be after it cools to 25 0 C?

I have 130 liters of gas in a piston at a temperature of C. If I cool the gas until the volume decreases to 85 liters, what will temperature of the gas be?

29 Combined Gas Law (Boyle and Charles): T must be in Kelvin Can be rearranged to: P 1 V 1 T 2 = P 2 V 2 T 1 A combined gas law problem can be recognized by having two sets of conditions. Note: if one set of parameters is unchanged that term will cancel on each side.

30 A balloon contains helium gas with a volume of 2.60 L at 25 o C and 768 mmHg. If the balloon ascends to an altitude where the helium pressure is 590 mmHg and the temperature is 15 o C, what is the volume of the balloon? What type of problem is this? There are 2 sets of conditions.

A balloon contains helium gas with a volume of 2.60 L at 25 o C and 768 mmHg. If the balloon ascends to an altitude where the helium pressure is 590 mmHg and the temperature is 15 o C, what is the volume of the balloon?