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Chem > Chem - Ch 17/18 (Intermolecular forces & their affects/water) > Flashcards

Chem - Ch 17/18 (Intermolecular forces & their affects/water) Flashcards

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1
Q

is solid water more or less dense than liquid

A

less

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2
Q

solids have a(n) (definite/indefinite) shape and/or volume

A

definite

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3
Q

liquids have a(n) (definite/indefinite) shape and/or volume

A

definite volume, indefinite shape

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4
Q

When a molecule in a liquid state undergoes a phase change to a gas, it must what

A

break all the intermolecular forces acting upon it

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5
Q

what four things are intermolecular forces related to

A

surface tension
vapor pressure
melting point
boiling point

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6
Q

what are the 3 types of intermolecular forces

A

dispersion
dipole-dipole
Hydrogen bonding

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7
Q

what three things affect boiling point

A

molar mass
polarity
intermolecular force

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8
Q

what is the relationship (usually) between molar mass and boiling point

A

directly proportional

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9
Q

what is the relationship between polarity and boiling point

A

directly proportional

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10
Q

what is the relationship between IMFs and boiling point

A

stronger IMF, boiling point goes up

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11
Q

why is solid water less dense than liquid water

A

the crystal structure of ice creates an open structure - a lot of empty space

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12
Q

What factor causes the high surface tension, low vapor pressure, and high boiling point of water

A

The hydrogen bonding

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12
Q

What factor causes the high surface tension, low vapor pressure, and high boiling point of water

A

The hydrogen bonding

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13
Q

What is surface tension

A

The inward force that minimizes the surface area of a liquid

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14
Q

Why does water always want to be in a sphere

A

Because of its high surface tension

A sphere is the smallest surface area for a given volume

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15
Q

Why does a needle or a coin float on water

A

Bc surface tension forms a “net” because if the strong attractions (H bonds) between the water molecules

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16
Q

How are temperature and kinetic energy related

A

Directly proportional

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17
Q

How are the strength of the IMFs and the rate of vaporization related

A

The stronger the IMFs, the slower the rate of evaporation

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18
Q

How can molecules escape from a liquid and become a vapor

A

they have to be on the surface (If it’s not boiling) and have enough kinetic energy

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19
Q

What happens to the rate of evaporation as the temperature increases

A

There is a faster rate of evaporation because a greater number of molecules have enough kinetic energy to evaporate

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20
Q

Evaporation is the opposite of what

A

Condensation

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21
Q

What will happen in respect to evaporation and condensation in a closed container

A

At some point the rates of evaporation and condensation will be equal

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22
Q

Why don’t the rates of evaporation and condensation ever equal out in an open container

A

The vapor molecules generally spread out faster than they can condense

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23
Q

What us dynamic equilibrium

A

When the rate of evaporation equals the rate of condensation

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24
Q

What us vapor pressure

A

The pressure exerted by the vapor when it is in dynamic equilibrium with its liquid

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25
Q

What is the relationship between IMF and vapor pressure

A

The weaker the IMF, the more molecules will be in vapor, so higher vapor pressure

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26
Q

Why does a weaker IMF mean higher vapor pressure

A

Because it’s easier to break weak IMFs, so more molecules become a vapor, which means higher vapor pressure

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27
Q

When there is a high vapor pressure, is it easier or harder for the liquid to evaporate

A

Easier

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28
Q

Why/how is evaporation a cooling process

A

When the high energy (warmer) molecules are lost from the liquid (bc they evaporate) it lowers the average kinetic energy. If energy is not drawn back into the liquid, it’s temp will decrease

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29
Q

Why do we sweat

A

To cool off - the warmer sweat drops leave our body, leaving behind cooler molecules, making us cooler

30
Q

What is heat of vaporization

A

The amount of heat energy required to vaporize one mole of the liquid

31
Q

What happens to the heat of vaporization as the polarity of a substance goes down/it has a weaker IMF

A

Heat of vaporization also goes down

32
Q

Why does the heat of vaporization decrease when polarity/strength of IMF decreases

A

Bc it takes less energy to vaporize something if the forces are weaker

33
Q

How are vapor pressure and temperature related

A

Directly proportional

34
Q

When does the boiling point occur

A

When vapor pressure is the same as the external pressure

35
Q

What is special about a boiling liquid

A

Molecules from anywhere in it, not just the surface, can vaporize

36
Q

What is the boiling point

A

The temperature required the have the vapor pressure equal the external pressure

37
Q

Why does water boil at a lower temperature on mt Everest

A

Because there is very low pressure there, so it requires less heat/energy to get the vapor pressure up to the external pressure

38
Q

What is another word for melting

A

Fusion

39
Q

What is heat of fusion

A

The amount of heat energy required to melt one mole of a solid

40
Q

Why is the heat of vaporization so much greater than the heat if fusion

A

Because in order to vaporize something, you need to completely overcome the intermolecular forces and when you melt something, you only need to loosen the attractions

41
Q

What is an equilibrium

A

Two states coexisting together

42
Q

What is the specific heat capacity

A

The amount of energy needed to raise the temperature of 1g of a substance by 1° C

43
Q

When water is at 0° C and 100° C what is the kinetic energy used for

A

To change the state of it, not raise them temperature

44
Q

What states of water exist at 0° C

A

Solid and liquid

45
Q

What states of water exist at 100° c

A

Liquid and gas

46
Q

What is the boiling point of water

A

100°C

47
Q

What is the freezing point of water

A

0°C

48
Q

What is the melting point of water

A

0°C

49
Q

The bonds between hydrogen and oxygen in a water molecule can be characterized as what

A

Intramolecular forces

Polar covalent bond

50
Q

When a water molecule forms a hydrogen bond with another water molecule, which atoms are involved in the interaction

A

A hydrogen from one molecule and an oxygen from the other molecule

51
Q

The freezing point of helium is approximately -270°C. The freezing point of Xenon is -112°C. What does this tell you about the IMFs in each molecule

A

The dispersion forces between the helium molecules are less than the dispersion forces between the xenon molecules

52
Q

What process must exist in equilibrium with the evaporation process when a measurement of the vapor pressure is made

A

Condensation

53
Q 
Put these forces in order of decreasing strength:
Covalent bonds
Dispersion forces
Ionic bonds
Hydrogen binds
Dipole dipole forces
A 
Ionic bonds
Covalent bonds
H bonds
Dipole dipole
Dispersion
54
Q

What types of elements make up molecular compounds

A

Non metals

55
Q

What types of elements make up atomic compounds

A

Noble gases

56
Q

What types of elements make up ionic compounds

A

A metal and nonmetal

57
Q

In terms of kinetic energy, explain how a molecule in a liquid evaporate

A

Only molecules with a certain minimum amount of kinetic energy can evaporate. When a liquid is heated, the KE of the particles in creases, which gives the molecules the boost they need to overcome the attractive forces keeping them from evaporating

58
Q

Why does the boiling point of a liquid vary w atmospheric pressure

A

Bc in order for a liquid to boil, external pressure must equal vapor pressure

59
Q

When does boiling happen

A

When a liquid is heated to a temperature at which particles throughout the liquid have enough KE to evaporate

60
Q

Why is there no change in intramolecular forces when a solid is melted

A

Melting is a physical change, so the composition doesn’t change, which means the intramolecular forces must stay the same

61
Q

Which is stronger: intermolecular forces or intramolecular forces

A

Intramolecular

62
Q

Which type of solid (ionic, molecular, or atomic) is most likely to have the highest melting pint

A

Ionic because ionic bonds are the the strongest force, so it takes more KE to loosen them

63
Q

Why does ammonia have a much higher boiling point than methane even though their molar masses are almost equal

A

Bc ammonia has H bonds so it takes more energy to overcome than dispersion forces which are present in methane

64
Q

Why does an alcohol rub on a person w a high fever cool them down

A

Alcohol evaporates really easily, and evaporation is a cooling process. As the particles w more kinetic energy, the hotter ones, evaporate, they leave behind the cooler ones.

65
Q

Why do an alcohol rub instead of a water rub

A

Alcohol evaporates easier than water bc there are no h-bonds holding the molecules together

66
Q

What is the relationship between vapor pressure and temperature

A

Directly proportional

67
Q

What is the relationship between kinetic energy and temperature

A

Directly proportional

68
Q

If heat is added to ice and liquid water in a closed container, and after the addition of the heat there is still ice and liquid water remaining, what happens to the vapor pressure and why?

A

The vapor pressure of the water will remain constant because the temperature stays constant (bc there is still water & ice) which means vapor pressure must also be constant bc VP and T are directly proportional

69
Q

Why is the density of ice less than the density of water

A

The same mass occupies a larger volume

70
Q

A 100g sample of water is heated from 50°c to 100° c. At 100°c, although heat is still being applied, the temperature does not rise. Explain why

A

100° C is the boiling point of water and also the point at which water vapor condenses. These two states, liquid and vapor, are in an equilibrium - they are coexisting together. At this temperature, the kinetic energy in the form of heat that is being applied is being used for the water to change states rather than to change the temperature of it

71
Q

Two molecules are the same size, but one has H-bonding and the other has dispersion forces. Which has the higher boiling point

A

The one that can h-bond

72
Q

Two molecules have the same intermolecular forces, but one is much bigger. Which will have the higher boiling point

A

The bigger one

73
Q

On what factors does the heat capacity of an object depend

A

Mass and chemical composition

Chem (20 decks)

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