Intermolecular forces test

Question 1

What are intermolecular forces?

Answer 1

The forces holding solids and liquids together(including attraction)

Question 2

What happens to intermolecular forces when a substance is melted or boiled?

Answer 2

The intermolecular forces are overcome, allowing something to change state

Question 3

What are London dispersion forces? What characteristics tell you a substance is experiencing London dispersion forces?

Answer 3

London dispersion forces occur when one instantaneous dipole induces another instantaneous dipole in an adjacent molecule or atom. A substance has LDF if it is covalent and nonpolar

Question 4

What are dipole-dipole forces? What characteristics of a substance tell you if it is experiencing dipole-dipole forces?

Answer 4

Dipole-dipole forces result from the attraction and repulsion of molecules, keeping them in motion. A substance is experiencing dipole-dipole forces if it is covalent, polar, and does not have hydrogen bonded N, O, or F

Question 5

What are ion-dipole forces? What characteristics of an atom determine if it is experiencing ion-dipole forces?

Answer 5

Ion-dipole forces are the interactions between an ion and a dipole. If a substance is ionic and polar it is experiencing ion-dipole forces.

Question 6

What is viscosity and its relationship with intermolecular forces and why?What happens to viscosity when you add heat?

Answer 6

Viscosity is the resistance of a liquid to flow. The more intermolecular forces there are, the more viscious or less flowing it is because the molecules are more attracted to each other. If you heat a liquid, it becomes less viscious, or more easily flows.

Question 7

What is surface tension and why does it occur?

Answer 7

Surface tension is when surface molecules of a liquid are attracted inwards towards the other liquid molecules, creating a skin like effect on the surface.

Question 8

What is meniscus and what causes it?

Answer 8

The curve shape of the liquid surface in a container. This is caused by cohesive and adhesive forces

Question 9

What are cohesive and adhesive forces and what do they contribute to meniscus?

Answer 9

Cohesive forces or forces binding molecules to each other and adhesive forces are forces binding molecules to a surface. Adhesive forces are responsible for the U-shaped of the meniscus curve and cohesive forces are responsible for making the meniscus curve go downward

Question 10

What is capillary action?

Answer 10

The tendency for water to be pulled up the side of a tube or container

Question 11

What is vapor pressure?

Answer 11

The pressure exerted on the surface containing a liquid when the liquid and vapor are in dynamic equilibrium.

Question 12

What is dynamic equilibrium? Why does this interaction occur?

Answer 12

Dynamic equilibrium is the point where where as many molecules escape the surface as strike the surface of a liquid. This happens because some of the molecules in the liquid have enough energy to escape the intermolecular forces holding them together and enter a gas phase

Question 13

What is vapor pressure’s relationship with intermolecular forces and why? What happens if dynamic equilibrium is never reached with a liquid?

Answer 13

More intermolecular forces results in lower vapor pressure because that results in the liquid molecules being more attracted to each other. If equilibrium is never reached, the liquid evaporates.

Question 14

What are crystalline solids?

Answer 14

Solids whose unit cell has a repeating pattern

Question 15

What are amorphous solids?

Answer 15

Solids whose unit cell lacks a repeating pattern

Question 16

What is the formula when calculating phase change when something is changing its phase?

Answer 16

Heat/enegery=mol•H(fus)/H(vap)

Question 17

What js the formula when calculating phase change when something is being heating in a single phase?

Answer 17

Heat=Mass•Change in Temp•Specific heat

Question 18

What is heat of fusion?

Answer 18

Energy needed to go from solid to liquid

Question 19

What is heat if vaporization?

Answer 19

Energy needed to go from liquid to gas

Question 20

What js the critical temperature?

Answer 20

The highest temperature that a liquid can form

Question 21

What is critical pressure?

Answer 21

Pressure required to form a liquid at critical temp.

Question 22

How do you calculate heat of vaporization?

Answer 22

1. Graph given pressures vs 1/given temp. (temp must be in K).
2. Determine slope of the line
   3: H(vap)= Slope/R

Question 23

What are metallic solids?

Answer 23

• Metals

* Have delocalized electrons

Question 24

What are ionic solids?

Answer 24

•Have ions at lattice points

Question 25

What are covalent-network solids?

Answer 25

• Have nonmetals or molecules at lattice points

* More forces than molecular solids

Question 26

What are molecular solids?

Answer 26

• Have nonmetals or molecules at lattice points

* Have less forces the covalent-network solids

Question 27

What physical properties are determine by strength of intermolecular forces in solids and liquids?

Answer 27

Attraction, boiling point, melting point, freezing point, viscosity, surface tension, cohesive/adhesive forces, vapor pressure, specific heat capacity

Question 28

What is the relationship between polarity and boiling point?

Answer 28

More polar=higher boiling point

Question 29

Where do you look on a graph for the normal boiling point?

Answer 29

The temperature at a pressure of 760 torr

Question 30

Where do you look on a phase diagram for freezing and boiling point?

Answer 30

Go to 1 atm. Increase in temp until you hit the solid/liquid line, that is freezing/melting point. Go further until you hit the liquid/gas line, that is the boiling point.

Question 31

How does average kinetic energy compare with average energy of attraction between solids, liquids, and gases?

Answer 31

Higher kinetic energy=lower attraction energy(indirect)

Question 32

How would increasing the temperature of a solid cause it to become a liquid then a gas?

Answer 32

It causes molecules to move and overcome the intermolecular forces holding them together

Question 33

What happens if you put a gas under extremely high pressure?

Answer 33

decrease in kinetic energy, increase in intermolecular forces

Question 34

How many atoms are in face and body centered unit cells?

Answer 34

Face centered: 4

Body centered: 2