Chapter 10-12 Notes: TEST

What causes weather?

Uneven heating of the atmosphere creates temperature and pressure differences, causing air movement and weather patterns

How are temperature, density, and pressure related?

Warm air is less dense and rises (low pressure); cold air is denser and sinks (high pressure)

Why does air move from high to low pressure?

Air moves toward equilibrium because higher pressure areas have more frequent particle collisions pushing outward

What causes gas pressure?

Collisions of gas particles with surfaces that create force per unit area

Why does increasing temperature increase pressure (constant volume)?

Higher kinetic energy makes particles move faster, causing more frequent and forceful collisions

Why does increasing volume decrease pressure?

Particles spread out, leading to fewer collisions per unit area

Why is atmospheric pressure highest at sea level?

More air above means more weight and more particle collisions

Why does pressure decrease with altitude?

Fewer air particles result in fewer collisions and lower pressure

What is a vacuum?

A space with no particles of matter

Is a perfect vacuum common?

No, true vacuums are nearly impossible; even space has some particles

What tool measures atmospheric pressure?

Barometer

What tool measures gas pressure in a container?

Manometer

How does a barometer work?

Atmospheric pressure pushes mercury up a column; higher pressure raises the mercury level

How does a manometer work?

It compares gas pressure to atmospheric pressure using fluid height differences

Why must units match in gas law calculations?

The gas constant depends on units, so mismatched units give incorrect answers

What is 1 atm equal to?

101.325 kPa = 760 mmHg = 760 torr = 1.013 × 10^5 Pa = 14.7 psi

What does Kinetic Molecular Theory say about gases?

Gases are made of tiny particles in constant random motion

Why is particle volume negligible in gases?

Particles are extremely small compared to the container volume

How much space exists between gas particles?

Mostly empty space

What forces exist between ideal gas particles?

None; no attraction or repulsion

What type of collisions do gas particles undergo?

Elastic collisions with no loss of kinetic energy

How do gas particles move?

In straight lines until they collide

What changes particle direction?

Collisions with other particles or container walls

What is conserved in elastic collisions?

Total kinetic energy

What determines average kinetic energy of a gas?

Temperature in Kelvin

What is temperature (particle level)?

The average kinetic energy of particles

What happens when a gas is heated?

Particles move faster and kinetic energy increases

Why must temperature be in Kelvin?

Kelvin measures absolute energy; gas laws require proportional relationships from zero energy

What happens to kinetic energy if temperature doubles (K)?

Average kinetic energy doubles

Difference between temperature and thermal energy?

Temperature is average kinetic energy; thermal energy is total kinetic energy of all particles

What is absolute zero?

0 K, the lowest possible temperature where particle motion is minimal

Why can particles never completely stop moving?

Quantum effects prevent complete rest

What is STP?

Standard Temperature and Pressure: 273 K and 1 atm

Why is STP used?

It provides a standard reference for comparing gas volumes

What is molar volume at STP?

1 mole of gas occupies 22.4 L at STP

When can you use 22.4 L/mol?

Only at STP

What is Boyle’s Law?

Pressure and volume are inversely proportional (P1V1 = P2V2)

Why does pressure increase when volume decreases?

Particles collide more frequently in a smaller space

Real

life example of Boyle’s Law?

What is Charles’s Law?

Volume and temperature are directly proportional (V1/T1 = V2/T2)

Why does volume increase with temperature?

Faster particles push outward more strongly

What is Gay

Lussac’s Law?

Why does pressure increase with temperature?

Faster particles collide more forcefully with container walls

What is the Combined Gas Law?

(P1V1)/T1 = (P2V2)/T2

When do you use the Combined Gas Law?

When pressure, volume, and temperature all change

What is the Ideal Gas Law?

PV = nRT

What does each variable in PV = nRT represent?

P is pressure, V is volume, n is moles, T is temperature in Kelvin

What are common R values?

0.0821 L·atm/mol·K, 8.31 kPa·L/mol·K, 62.4 mmHg·L/mol·K

When does the Ideal Gas Law fail?

At high pressure or low temperature when real gas behavior matters

What is Dalton’s Law?

Total pressure equals the sum of partial pressures (Ptotal = P1 + P2 + …)

Why can partial pressures be added?

Each gas acts independently in a mixture

What determines pressure contribution in a mixture?

Number of particles (moles), not identity

What is Graham’s Law?

Rate of diffusion is inversely proportional to the square root of molar mass

Graham’s Law equation?

rate1/rate2 = √(m2/m1)

Which gases diffuse faster?

Lighter gases with lower molar mass

Common Graham’s Law mistake?

Flipping the mass ratio incorrectly

What is Avogadro’s Law?

Volume is directly proportional to moles (V1/n1 = V2/n2)

Why does volume increase with moles?

More particles require more space due to increased collisions

What is the gas stoichiometry strategy?

Convert liters to moles, use mole ratio, then convert to desired units

What is sublimation?

Solid directly to gas

What is deposition?

Gas directly to solid

What is vaporization?

Liquid to gas

What is condensation?

Gas to liquid

What determines phase of matter?

Temperature and pressure

Why does increasing pressure favor liquids or solids?

Particles are forced closer together

What is a phase diagram?

A graph showing phases at different temperatures and pressures

What is the triple point?

All three phases exist in equilibrium

What is the critical point?

Point where liquid and gas become indistinguishable

Why does boiling point increase with pressure?

Higher pressure makes it harder for particles to escape into gas phase

What weather is associated with high pressure?

Clear skies and stable conditions

What weather is associated with low pressure?

Clouds, precipitation, and unstable conditions

Why does low pressure cause storms?

Rising air cools and condenses into clouds and precipitation

Temperature conversion to Kelvin?

K equals Celsius plus 273

Temperature conversion to Celsius?

Celsius equals Kelvin minus 273

Why must units stay consistent in calculations?

Inconsistent units lead to incorrect results

What are the most common test mistakes?

Using Celsius instead of Kelvin, wrong R value, using 22.4 L outside STP, flipping ratios, misidentifying gas law