Phase Change Review

Where on the curve is the potential energy changing?

a. A, B, C

b.B-C, C-D, E-F

c. A-B, C-D

d.B-C, D-E

What is the total number of joules of heat energy absorbed by 15 grams of water when it is heated from

30°C to 40°C?

a. 10

b. 63

c. 150

d. 630

The phase changes B → C and D → E are not associated with temperature increases because the energy is used to

a. increase the velocity of molecules

b. break bonds between atoms

c. rearrange atoms within molecules

d. increase the density of the sample

e. break intermolecular forces

How much energy(kJ) is required to convert a 15.5 g water at 5.0oC to water vapor at 180oC?

a. 56

b. 9.0 x 103

c. 11

d. 44

e. 27

At this point, the substance represented by the phase diagram will be undergoing sublimation.

a. A

b. B

c. C

d. D

e. E

This point represents a boiling point of the substance

a. A

b. B

c. C

d. D

e. E

When a substance undergoes a phase change from liquid to solid, which of the following will occur?

a. Energy will be released by the substance because intermolecular forces are being weakened.

b. Energy will be released by the substance because intermolecular forces are being strengthened.

c. Energy will be absorbed by the substance because intermolecular forces are being weakened.

d. Energy will be absorbed by the substance because intermolecular forces are being strengthened.

e. The energy of the substance will not be changed.

During which of the following phase changes must heat be added to overcome intermolecular forces?

I. Vaporization

II. Sublimation

III. Deposition 

a. I only

b. II only

c. I and II only

d. I and III only

e. III only

 

In which of the following are the intermolecular forces listed from the weakest to strongest?

a. Dipole-dipole > LDF > hydrogen bonds

b. LDF < dipole-dipole < hydrogen bonds

c. Hydrogen bonds < dipole-dipole < LDF

d. LDF < hydrogen bonds < dipole-dipole

 

C30H62 is a nonpolar compound that is a solid at room temperature, and water is highly hydrogen bonded but is a liquid because

a. water molecules are very light.

b. water molecules ionize easily.

c. the 62 hydrogen atoms in C30H62 allow for many instantaneous dipoles that exceed the attractive force of a hydrogen bond.

d. C30H62 is so large that it cannot melt.

e. C30H62 has a lower melting point if dissolved in nonpolar hexane.

A liquid substance that exhibits low intermolecular attractions is expected to have

 a. Low viscosity, low boiling point, and low heat of vaporization

b. High viscosity, low boiling point, and low heat of vaporization

c. Low viscosity, high boiling point, and low heat of vaporization

d. Low viscosity, low boiling point, and high heat of vaporization

e. High viscosity, high boiling point, and high heat of vaporization

  

Calculate the amount of heat required to completely

convert 50 g of ice at -10 ºC to steam at 120 ºC. a. 27.2kJ

b. 137kJ

c. 154kJ

d. 24kJ

Which contains more energy, water at 100oC or steam at 100oC?

a. Water

b. Steam

c. They both contain the same amount of energy

d. Not enough information to determine