Homework #1: Vapor Pressure

Chapter 3: Gases Aim # 1 : How can you describe pressure?

There are four liquids in table H, which one do you recognize and use in your daily life? Water

Do you know the common name for propanone, ethanol, and ethanoic acid? Propanone: acetone Ethanoic acid: vinegar Ethanol: alcohol (there are different types of alcohols)

Use table k and identify the formula for ethanoic acid CH3COOH HC2H3O2

Use the reference table P and find the meaning of the prefix eth and prop Eth: 2 carbons Prop: 3 carbons

Use your reference table H and find the boiling point of propanone, ethanol, water and ethanoic acid at 101.3 KPa Propanone:56 Ethanol: 78 Water: 100 Ethanoic acid: 117

Why does ethanoic acid have a very high boiling point? The intermolecular forces are very strong.

Where do we use propanone or acetone in our daily life? Manicure…

Propanone is liquid at room temperature, the boiling point at STP is 56oC, this compound goes from liquid to gas very fast. Why? Weak intermolecular forces introduce the word volatile

1. What happens when you open a coke can. 2. What do you hear. 3 1. What happens when you open a coke can? 2. What do you hear? 3. Do you have a theory for what is going on?

Why is it difficult to boil an egg on Mt. Everest?

Where do you observe more pressure? Why?

Why does woman wearing snow shoes stay on top of the snow and the two girls sink in the snow?

What is pressure? Pressure is defined as a measure of the force applied over a unit area. 

1. Pressure Pressure is defined as a measure of the force applied over a unit area.  Pressure = Force Area

What are the units of pressure?

How do we measure pressure? Barometer: atmospheric pressure 2. Manometer: gas pressure measures the difference between two different points of pressure.

What is STP in chemistry?

2. Units of Pressure: Table A

What is the relationship between atmospheric pressure and weather conditions?

Atmospheric Pressure Changing weather conditions

When the air sinks, more force pushes down toward the ground, so the barometric pressure increases. Conversely, when a low-pressure area moves in, the air rises, cools and condenses out moisture, which forms clouds and precipitation. Since a rising column of air above weighs less, the barometric pressure falls.

How does altitude affect pressure? At sea level, the weight of the air presses on us with a pressure of approximately 14.7 lbs/in2. At higher altitudes, less air means less weight and less pressure. Pressure and density of air decreases with increasing elevation. 

Atmospheric Pressure Changing Altitude

Sea Level STP: 101.3 Kpa or 1 atm Table A

Mount Everest STP: 71 KPa

A. Barometer: device to measure air pressure 3. Measuring Pressure Empty space (a vacuum) Hg Weight of the mercury in the column atmosphere (atmospheric pressure) A. Barometer: device to measure air pressure

Pressure The mercury in the inverted tube is pushed upward by the force of atmospheric pressure pushing down on the surface of the mercury in the dish. The height of the mercury in the tube changes with changing atmospheric pressure. Under conditions of standard atmospheric pressure, the height of the mercury in the tube is 760 mm.

B. Manometer

4. Units of Pressure 1 atmosphere or 1 atm 101.3 kilopascal or Kpa 760 millimeters of mercury or mm Hg 760 torr

5. Boiling vs. Evaporation

A. Boiling Normal boiling point of H2O : 100 ºC atmospheric pressure = vapor pressure ATMOSPHERIC PRESSURE Normal boiling point of H2O : 100 ºC VAPOR PRESSURE

A liquid boils at a temperature at which its vapor pressure is equal to the pressure of the gas above it.

What is the difference between boiling point and evaporation?

B. Evaporation Molecules go from liquid to gas phase gas H2O evaporates at different temperature. liquid

Test your Understanding

1. Convert 1 atm to KPa 101.3 Kpa 101.3 KPa 1 atm 101.3 KPa 1 atm 1 atm x 101.3 KPa 1 atm = 101.3 KPa 100 KPa

2. . Convert 0.927 atm to KPa 0.927 atm X 101.3 Kpa = 1 atm

3. The air pressure for a certain tire is 109 kPa 3. The air pressure for a certain tire is 109 kPa. What is this pressure in atmospheres? 1 atm 101.3 Kpa 109 Kpa X = 1.08 atm

Pressure Practice Convert the following: 145 mm Hg into kpa 900 mm Hg into torrs 4580 Pa into kPa 450 psi into kPa 5. 25 psi into atm 6. 150 atm into KPa 109 kPa into atm 76.9 mm Hg into atm 98.6 torr into kPa 3 atm into kPa

End of the show