CHEM 12*

Identify the state of matter that is the most compressible.

gas

Explain why ice floats in water.

ice is less dense than water

A molecule can hydrogen bonding if it contains hydrogen covalently bonded to

fluorine, oxygen, or nitrogen

boiling point increases in which direction?

down the perodic table

For automobile engines, identify the best choice of motor oil.

low viscosity for Maine in the winter and high viscosity for Florida in the summer

A hair floating on the top of water is an example of

surface tension.

Give the change in condition to go from a gas to a solid

cool or increase pressure

Give the term for the temperature at which the gas and liquid phases form a supercritical fluid.

critical temperature

Define deposition.

A gas becomes a solid.

On a phase diagram, the sublimation curve is between

a solid and a gas.

Define critical point.

The temperature and pressure above which a supercritical fluid exists.

Why do O, F and N, when bonded to H, form such strong intermolecular attractions to neighboring molecules? Make sure to be specific. (SAR)

Because O, F, and N are very electronegative, they form polar bonds with hydrogen. This makes hydrogen atoms slightly positive, which are attracted to lone pairs on nearby O, F, or N atoms, creating strong hydrogen bonds between molecules.

Why is the ΔHvap higher than ΔHfus for a given compound? (SAR)

vaporizing a substance requires more energy to completely overcome all intermolecular forces, while melting only requires enough energy to partially overcome them.

Which one of the following has a definite shape and volume?

solid

Identify the compound with the highest boiling point.

H2O

What type of intermolecular force causes the dissolution of KI in water?

ion-dipole force

Define condensation.

A gas becomes a liquid.

Describe sweating in humans.

The skin is cooled, The sweat evaporates absorbing heat from the body, and It is an endothermic reaction.

The melting point of ice is .

0°C

On a phase diagram, the fusion curve is between

a solid and a liquid.

Define boiling point of a liquid. (SAR)

The temperature at which a liquid's vapor pressure equals the external pressure.

Which one of the following could be in a crystalline state?

solid

In a liquid, the tendency of liquids to minimize their surface area is called

surface tension.

Capillary action occurs because

adhesive forces are greater than cohesive forces.

Define fusion.

the phase transition from solid to liquid

Define sublimation.

the phase transition from solid to gas

The normal boiling point of water is at sea level.

212°F

On a phase diagram, the vaporization curve is between

a liquid and a gas.

Define volatile. (SAR)

a substance that readily vaporizes or turns into a gas at a relatively low temperature

Why does the temperature of a substance stay constant during a phase change such as vaporization? (SAR)

because the added heat energy isn't increasing the molecules' speed but is instead used to overcome the strong intermolecular forces holding them together, allowing them to break free and transition into a new phase

Identify the place which has the highest boiling point of water.

Death Valley, 282 feet below sea level

at high temperatures and low pressures

gas

moderate temperatures and pressure (middle)

liquid

at low temperatures and moderate to high pressures

solid

where the solid liquid and gas lines meet

triple point

Identify the characteristics of a liquid.

indefinite shape, but definite volume

Identify the substance with the highest viscosity.

corn syrup

Which of the following statements is FALSE?

Molecules with hydrogen bonding are more volatile than compounds with dipole-dipole forces.

Consider the phase change diagram shown here. Identify the state present at point a.  

Solid/liquid equilibrium or fusion curve