Gas Behavior, part 1 January 12, th grade Chapter 4.3

Scientist of the Day

Joseph Louis Gay-Lussac Father arrested in the French Revolution so he was raised by an abbot Used hot air balloons to find gas laws, gave credit to Charles Found 2 new elements Figured out formula for water Married an unimportant shop girl because he saw her reading a chemistry book

How does a hot air balloon work?

Gas Molecules What will happen if we increase the temperature of a gas? Temperature: the energy of molecules moving

Increasing Temperature If the temperature goes up, the gas molecules move faster If the molecules are moving faster, they’ll hit the sides more often This increases pressure If you want to keep pressure the same, you have to increase volume instead

Charles’ Law Temperature goes up, volume goes up Temperature and volume are directly proportional T ∝ V

Graphing Charles’ Law Temperature (K) Temperature (°C) Volume (mL)

Graphing Charles’ Law Charles’ law is a case where we have to use K If we graphed with °C instead of K, we wouldn’t be directly proportional Sometimes we’d have a negative temperature with a positive volume – that’s not directly proportional Kelvin can never be negative, so it fixes the problem!

Pressure Since gas molecules fill the entire container and are constantly moving, they are constantly banging into the sides of their container This is called pressure Pressure can be used for liquids & solids, but then you have to worry about gravity too

Increasing Pressure

Boyle’s Law Boyle’s Law looks at volume and pressure Volume and pressure are inversely proportional Inversely proportional: when one goes up, the other goes down

Graphing Boyle’s Law Volume (mL)Pressure (kPa)

Graphing Boyle’s Law Shows up as a curve Any time we multiply volume x pressure for the same amount of gas, we’ll get the same number

Vaporization Vaporization: liquid  gas Can be caused by evaporation or boiling Add thermal energy Evaporation: liquid  gas, below the boiling point Only some liquid molecules have enough energy to escape their bonds to other liquid molecules No boiling Boiling: liquid  gas, getting hotter Happens at the boiling point Bubbles of gas form at & below the surface

Graphing Changes of State