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Here is your whirlwind through the early gas laws

Here is your whirlwind through the early gas laws. Boyle’s Law. His law gives the relationship between pressure and volume if temperature and amount are held constant If the volume of a container is increased, the pressure decreases

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Here is your whirlwind through the early gas laws

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  1. Here is your whirlwind through the early gas laws

  2. Boyle’s Law • His law gives the relationship between pressure and volume if temperature and amount are held constant • If the volume of a container is increased, the pressure decreases • If the volume of a container is decreased, the pressure increases • WHY?!

  3. Boyle’s Law Continued: • Boyle’s Law: P1V1 = P2V2 • For any gas, the product of the pressure and the volume before a change is equal (=) to the product of the pressure and the volume after a change

  4. Just read the following statements… • When considering Boyle’s Law, which is P1V1 = P2V2 • Suppose the volume is increased. This means gas molecules have farther to go and they will impact the container walls less often per unit time. This means the gas pressure will be less because there are less molecule impacts per unit time. • If the volume is decreased, the gas molecules have a shorter distance to go, thus striking the walls more often per unit time. This results in pressure being increased because there are more molecule impacts per unit time

  5. Charles’ Law • If you increase the temperature of a gas, the volume also increases • (Note: The temperature must be in Kelvin, NOT degrees centigrade) • Why? • The KMT tells us that the amount of energy that a gas has is determined by the temperature of the gas. The more energy a gas has, the faster the gas molecules move away from each other, causing more space between the molecules and a larger overall volume

  6. Charles’ Law Continued • Charles' Law is a direct mathematical relationship. This means there are two connected values and when one goes up, the other also increases • **Notice**: the right-hand equation results from cross-multiplying the first one. Some people remember one better than the other, so both are provided • Understanding check… • What kind of relationship was involved in Boyle’s Law?

  7. Gay-Lussac’s Law • Gives the relationship between pressure & temperature when volume & amount are held constant • If the temperature of a container is increased, the pressure increases • If the temperature of a container is decreased, the pressure decreases

  8. Gay-Lussac’s Law Cont. • Why? • Suppose the temperature is increased. This means gas molecules will move faster and they will impact the container walls more often. This means the gas pressure inside the container will increase, since the container has rigid walls (volume stays constant) • Gay-Lussac's Law is a direct mathematical relationship. This means there are two connected values and when one goes up, the other also increases

  9. Gay-Lussac’s Law • Notice the similarities to the Charles' Law graphic. This is because both laws are direct relationships.

  10. Getting to the Combined Gas Law • Here is one way to "derive" the Combined Gas Law:

  11. The Combined Gas Law If we put the last three gas laws together, we can devise another law that encompasses all three of them (making it unnecessary to memorize the three): • How to use this law: Whenever you have a problem in which you change the pressure, volume, and/or temperature, just plug the values into it. • If one of the variables isn’t mentioned, we can assume that it’s kept constant and we can just cross it out of the equation.

  12. Analogies • For HW (in addition to your already listed HW), please come up with an analogy/metaphor that helps YOU understand one or all of the Gas Law relationships! • Example: The analogy of a school dance can be used to illustrate many gas relationships. For example, if you increase the size of the room (volume), the pressure of dancers decreases, or if you decrease the size of the room (volume), the pressure of the dancers dramatically increases!

  13. Example Problems: • What will the final pressure of a gas sample be if it is initially at 2.0 atm and the volume is changed from 42 L to 124 L at constant temperature? • What is the volume of a gas sample at 0.95 atm and 25 °C, if its volume is 26 L at 1.2 atm and 14 °C? • 5.00 L of a gas is collected at 22.0°C and 745.0 mmHg. When the temperature is changed to standard, what is the new pressure?

  14. End of:Whirlwind through the early Gas Laws! HW: Complete Gas Laws Review Lab Activity (if not completed by end of class) AND Read pgs: 418-425, take 10 bullet notes & complete problems #7, 9, 11, 13, & 20 AND Write your own Analogy for a Gas Law Relationship

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