ch 171 - chapter 6 (states of matter, gas laws, pressure, kinetic theory of matter)

Freezing

liquid to solid

Melting/fusion

solid to liquid

Vaporization

Liquid to gas

Condensation

Gas to liquid

Sublimation

solid to gas

Deposition

gas to solid

Is freezing exothermic or endothermic?

Exothermic (heat is LEAVING water, so it freezes)

Is melting endothermic or exothermic?

endothermic (ice takes in thermal energy via heat to become liquid)

Is vaporization endothermic or exothermic?

endothermic (liquid molecules move slower than gas molecules, so they take in energy to move faster)

Is condensation endothermic or exothermic?

exothermic (gas molecules are faster than liquid molecules, so energy is released as the particles start to move slower)

Is sublimation endothermic or exothermic?

endothermic (solid particles are slower than gas molecules, so the solid particles must take in energy to move faster)

Is deposition endothermic or exothermic?

exothermic (gas molecules are faster than solid molecules, so the gas molecules lose energy as they have to move slower to become a solid).

If delta H is positive, the reaction is

endothermic, heat is absorbed

If delta H is negative, the reaction is

exothermic, heat is released

STP

0 degrees celsius and 1 atm

normal boiling point of water

100.00 degrees celsius

normal freezing point of pure water

0.00 degrees celsius

density of water

1.00 g/mL

1 calorie meaning

the energy needed to raise temperature of 1 grams of water by 1 degree celsius

molarity

mol/L (M)

w/w %

mass of solute/mass of solution x 100

v/v %

volume of solute/volume of solution x 100

w/v %

mass of solute/volume of solution x 100

how to get celsius given farenheight

C = 5/9 (F-32)

What does particle speed depend on?

Temperature

When particles collide, do they lose kinetic energy?

No, they don’t. There is no net energy loss in the system. This makes them elastic.

Do particles experience attractive or repulsive forces normally?

No. Ideal gases don’t experience any repulsive or attractive forces. They only experience attractive or repulsive forces during collisions.

Pressure in gases is caused by what?

Collisions of gas particles with the walls of the container.

The more frequent and energetic collisions of gas particles are in a container, what is true of its pressure?

The pressure is higher.

Boyle’s Law

Pressure and volume are inversely proportional at a constant temperature. When volume decreases, pressure increases.

Charles’ Law

Volume and temperature are directly proportional at constant pressure. If temperature increases, the volume of the gas expands, and vice versa.

Avagadro’s Law

Volume and number of gas particles are directly proportional at a constant temperature and pressure. If you add more gas molecules to a fixed container, the volume increases.

What does the kinetic theory assume? Why is this not likely to occur?

The kinetic theory assumes that real gasses behave like ideal gases. It assumes that there are no attractive forces between particles, but real gasses experience intermolecular forces (like van der waal forces).

When pressure is high, is the volume of particles significant or not?

the volume is significant

At low temperature, what is true about gas particles? What about IMFS?

They move slowly, and IMFS become more noticeable.

When a liquid boils into a gas, what is true about the particles in relation to IMFS?

The particles gain enough energy to OVERCOME intermolecular forces and escape the liquid phase.

As kinetic energy of particles of a gas increase, what is true of the temperature?

The temperature is increasing

What does the pressure of a gas depend on in respect to collisions?

The pressure of a gas depends on the frequency and force of collisions between gas molecules and the walls of the container

Boyle’s Law equation

P1V1 = P2V2

Charles’ Law equation

V1/T1 = V2/T2

Ideal gas law equation

PV = nRT

Combined gas law

Combines Boyle’s, Charles, and Gay-Lussac’s laws into one equation. Says that pressure and volume are inversely related to each other, and that they are both directly related to temperature.

Combined gas law equation

P1V1/T1 = P2V2/T2

What is the kinetic energy of particles related to?

The kinetic energy of particles is related to the temperature of the substance

Average kinetic energy of particles in a substance is ____ proportional to the temperature in kelvin.

Directly (this is why when you heat a substance, the particles move faster and this increase in movement corresponds to a higher temperature).

What increases rate of diffusion?

High temperatures, because particles will move faster and thus, diffuse quicker

What is true about ideal gases in respect to the kinetic theory of matter, IMFS, and elastic collisions?

What is true about ideal gases is that they perfectly follow the kinetic theory of matter, with no intermolecular forces, and perfectly elastic collisions.

When do real gases deviate from ideal behavior? How?

At high pressures or low temperatures, where IMFS become significant and particle volumes are no longer negligible.

Dalton’s Law

Total pressure exerted by a mixture of gases is the sum of the partial pressures of the individual gases in the mixture

Partial pressure

The pressure that each gas in a mixture would exert if it occupied the same volume by itself

Dalton’s law equation

Ptotal = P1 + P2 + P3….+Pn

are gases assumed to be ideal in Dalton’s law?

Yes. In dalton laws, the gases don’t interact chemically (ideal gases).

In Dalton’s law, each gas in the mixture exerts its pressure _____ of the others

Independently

Graham’s Law of diffusion/effusion

Rate of diffusion (or effusion) of a gas is inversely proportional to the square root of its molar mass

Rate of diffusion

How quickly a gas spreads through space or a medium

Rate of effusion

The rate at which a gas passes through a tiny hole into a vacuum

The lighter a gas (lower molar mass), the ____ it will diffuse/effuse. The heavier a gas (higher molar mass), the ____ it will diffuse/effuse

Faster, slower

Evaporation

Process by which molecules at the surface of a liquid gain enough energy to overcome IMFs and escape into the gas phase, even if the liquid is below its boiling point

Surface phenomenon

Evaporation only happens at the surface of the liquid because only surface molecules can escape into the gas phase

Is evaporation endothermic or exothermic? Why?

It’s endothermic because molecules require energy (heat) to overcome the attractive forces between them in the liquid state.

When temperature increases, how does this affect evaporation?

higher temperatures give molecules more kinetic energy, making it easier for them to escape the liquid

How does surface area affect evaporation?

Larger surface area allows more molecules to escape, so evaporation happens faster

Do molecules with strong IMFS evaporate faster or slower than molecules with weaker IMFS?

Molecules with stronger IMFs evaporate SLOWER because they need more energy and time to overcome their IMFS in order to evaporate

evaporative cooling

When a liquid evaporates, it cools down because the fastest-moving (hottest) molecules leave, lowering the average kinetic energy of the remaining liquid. This is why sweating cools you down.

Evaporation is the _____ transition from liquid to gas below the boiling point

Slow

Boiling is the ____ process where the liquid transition to gas throughout the liquid at its boiling point

Fast

Vapor pressure

Pressure exerted by the vapor (gas) of a substance when it is in equilibrium with its liquid or solid phase at a given temperature

Equilibrium

Vapor pressure is reached when the rate of evaporation equals the rate of condensation (the process where gas molecules return to the liquid phase).

As temperature increases, what is true of vapor pressure?

Vapor pressure increases because more molecules have enough energy to escape from the liquid into the vapor phase.

What is true about the vapor pressures of substances with stronger IMFS?

Substances with stronger IMFS have LOW vapor pressure, and they evaporate more slowly.

Volatile

Substances with higher vapor pressure (like alcohol or acetone) evaporate quickly

The vapor pressure of the liquid exceeds the atmospheric pressure, the liquid will do what?

The liquid will boil (but below this point, evaporation will occur and vapor pressure will gradually increase as more molecules escape into the vapor phase)

Boiling point

The temperature at which the liquid’s vapor pressure equals the external (atmospheric) pressure. At this point, liquid molecules throughout the liquid will turn into gas, not just those at the surface. At 1 atm, water boils at 100 degrees Celsius.

As temperature increases, what happens to vapor pressure?

As temperature increases, vapor pressure increases

When does boiling occur?

Boiling occurs when vapor pressure = atmospheric pressure.