TeleSchool Week 15 (April 20-24): Boyle’s Law, Charles’ Law, and Combined Gas Law 1. Complete the following notes by watching both of these videos: https://youtu.be/B7WpVFKj5ZU and https://youtu.be/hckF9MXpxE4 2. Review the worked-out problems I provided in this handout. 3. For your week 15 grade, please complete the quiz named “2-or-3 variable gas laws 2020” in MiltonMoodle.com. It is due by 11:59 pm on Friday, April 24 th . 4. Need more help? See these videos: https://www.youtube.com/watch?v=kOp-3CMb6nY and https://www.youtube.com/watch?v=bftkRnTcFj8 Characteristics of Gases Properties of Gases: 1. Their volume is ___________. 2. They have low _________ due to the large spaces in between particles. Kinetic Molecular Theory : Relates to a gas in ideal conditions 1. Individual particles have no _________ .Volume of the gas is calculated by adding up the total volume of all the particles, including the distance between them. 2. The particles move in constant, rapid, random _________ in straight lines until they collide with other particles. 3. The collisions are completely __________, meaning no energy is lost or gained. This is in contrast to, say, pool (billiards) when the cue ball transfers its energy to another ball. 4. Average kinetic energy is directly related to the temperature. Temperature will ALWAYS be measured in Kelvins. Ex. 400 m/s at 298 K = 400 m/s at room temperature (25°C). Four Variables that Describe a Gas : 1. The average kinetic energy depends on the ____________. The Kelvin scale is used which is based on absolute zero. Absolute zero is the temperature at which all molecular motion stops: 0 K.
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TeleSchool Week 15 (April 20-24): Boyle’s Law, Charles’ Law, and Combined Gas Law
1. Complete the following notes by watching both of these videos: https://youtu.be/B7WpVFKj5ZU and https://youtu.be/hckF9MXpxE4
2. Review the worked-out problems I provided in this handout.3. For your week 15 grade, please complete the quiz named “2-or-3 variable gas laws 2020” in
MiltonMoodle.com. It is due by 11:59 pm on Friday, April 24th. 4. Need more help? See these videos: https://www.youtube.com/watch?v=kOp-3CMb6nY and
https://www.youtube.com/watch?v=bftkRnTcFj8
Characteristics of Gases
Properties of Gases:1. Their volume is ___________.2. They have low _________ due to the large spaces in between particles.
Kinetic Molecular Theory: Relates to a gas in ideal conditions1. Individual particles have no _________ .Volume of the gas is calculated by adding up the total volume of all the particles, including the distance between them.
2. The particles move in constant, rapid, random _________ in straight lines until they collide with other particles.
3. The collisions are completely __________, meaning no energy is lost or gained. This is in contrast to, say, pool (billiards) when the cue ball transfers its energy to another ball.
4. Average kinetic energy is directly related to the temperature. Temperature will ALWAYS be measured in Kelvins. Ex. 400 m/s at 298 K = 400 m/s at room temperature (25°C).
Four Variables that Describe a Gas:1. The average kinetic energy depends on the ____________. The Kelvin scale is used which is based on absolute zero. Absolute zero is the temperature at which all molecular motion stops: 0 K.
To convert from ________ to Kelvin, keep in mind that K= °C + 273
2. Volume can be measured in liters (L) or milliliters (mL). Make sure your ________ agree!
3. Gases exerts a force known as ________. Pressure is created when particles bump into the sides of the container. Pressure is equal to force divided by area. Pressure is proportional to the number of collisions.
4. Standard_______________ and standard pressure are used as a reference to allow comparisons between different sets of experimental measurements (ex. a gas collected at sea level vs. one collected on top of a mountain).
Boyle’s and Charles’ Laws
Gas Laws (general):
The behavior of a gas depends upon its environment. The greater the temperature, the faster it moves. The number of _____________ is directly proportional to the pressure of the gas. Directly proportional= as one increases, the other ____________.Ideal conditions for a gas are called Standard Temperature and Pressure (_____). We use these conditions to be able to compare them to experimental conditions.
__________ Pressure: 101.3 kPa (kilopascals) Standard ___________: 273 K = 0 °C________ temperature is 25.0 °C
Boyle’s Law:The volume of a gas is __________ proportional to the pressure of a gas. If you increase the volume, pressure decreases. If you decrease the volume, pressure ____________. Ex. As you squeeze a balloon, its volume decreases.
Temperature is kept constant so it is absent from the formula.
Formula: P1V1 = P2V2 V= volume, which can be L, mL, cm3, m3, or dm3 P = pressure, which can be kPa, mm Hg, or atm
Example: A container holds 125 mL of a gas at 89.1 kPa. What will the volume of the gas be if the pressure is changed to standard pressure?
Charles’ Law:The volume of a gas is ___________ proportional to the temperature of the gas. If you increase the temperature, volume ____________. If you decrease the temperature, volume decreases. Ex. Helium-filled balloons appear to deflate somewhat when taken outdoors in cold weather.
Pressure is kept constant so it is absent from the formula.
Formula: V1 = V2
T1 T2
V= volume (L or mL) T = temperature, which must be in Kelvin (not Celsius!)
Example: A container holds 35.4 mL of a gas at room temperature. What will the volume be when the temperature drops to 19.5°C?
Example #2: Be ___________ when you are solving for a variable on the __________ of a fraction. You will need to __________________ to get the right answer reliably.
When gas in a 21.7 L container at standard temperature is moved into a 1270 mL container, what is its final temperature?
Combined Gas Law: What happens if all ______ variables (P, V, and T) change at the same time?
On a spring day like this one, sometimes my car has the “low tire pressure” warning signal on in the early chill of the morning. That’s because the air particles inside the tire are _______ (low T), leading to them crowding together and taking up _______ space (low V). That results in _________ collisions with the walls of the tire (low P), making driving dangerous.
If I add more air, the particles will take up _______ space (higher V) and bounce off the tire walls more frequently, leading to a safer (_________) pressure. The same effect will happen as the day heats up because the temperature increases with the sunlight, leading to higher pressure. P and T are directly proportional. As P goes up, so does T.
How does the combined gas law look? Just ___________ Boyle’s Law with Charles’ Law.
P1V1 = P2V2 and V1 = V2 give us P1V1 = P2V2 T1 T2 T1 T2
Just like in Charles’ Law, Celsius is ________used in the formula because it has negative values, which give us answers that make no sense. So, always convert ___________ temperatures to Kelvin by adding 273. Make sure your ___________ are both mL or both L, too.
Here are two examples.
1. A 78.9 mL container of gas at 25°C and 195.4 kPa is moved to STP. What is its final volume?
2. A gas has a volume of 1.75 L at -23.0°C and 152 kPa. At what temperature would the gas occupy 1370 mL at 215 kPa?
Your goals for gas laws: be able to RECOGNIZE what formula to use, CONVERT any units that don’t agree, and SOLVE for any unknown variable.
Hint: You can always use the Combined Gas Law and just eliminate the variables that don’t change OR just put in the same value for the first AND second condition for that variable. (See #5 below.)
Here are some more problems, including a few that have tricky parts you’ll want to understand to ace the Moodle quiz.
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