Chemistry 8P11 - States of Matter

Question 1

Define:

★Matter

Answer 1

Matter is anything that has mass and takes up space (made of atoms).

Question 2

Give the:

★Density Equation

Answer 2

ρ = m/V

Where:

• Mass (m) - the amount of matter in an object, measured in grams (g, kg, etc.)
• Volume (V) - how much space an object or substance takes up, measured in milliliters (mL) or cubic centimeters (cm3).
• Density (ρ) - given by the Greek letter “rho”

Question 3

★Mass and weight aren’t the same thing. What units are used to measure weight?

Answer 3

newtons or pounds

Be careful! Mass and weight are NOT the same thing. Mass is measured in grams, whereas weight is measured in newtons or pounds. You will have the same mass on Earth as do on Mars, but not the same weight. Weight = mass*gravity. Earth’s gravity = 9.8 N/kg

Question 4

Define and give the examples of:

a phase (or state of matter)

Answer 4

A phase is a physically distinct form of a substance. Also called “state of matter”.

Solid, liquid, and gas are the three phases of matter that most chemistry courses will test.

Question 5

Name 3 characteristic of the solid phase of matter:

★ gas phase

Answer 5

1. molecules are widely spaced, take shape of the container
2. molecules move quickly
3. molecular forces are weak between molecules

Question 6

Name 3 characteristic of the liquid phase of matter:

★ liquid phase

Answer 6

1. molecules or inert atoms are constantly in contact with others
2. molecules move more quickly than solids, but slower than gases
3. molecular forces are weaker than solids, but stronger than gases

Question 7

Name 3 characteristic of the solid phase of matter:

★ solid phase

Answer 7

1. atoms are closely spaced and may vibrate in position
2. atoms do not change relative locations,
3. solids may be formed from molecules, or they may be extended structures with repeating subunits (ex: crystals)

Question 8

★Which two variables can be used to actively change the phase of a substance?

Answer 8

Temperature can be added or removed. In general, an increase in temperature drives the phase change solid⇒liquid⇒gas.

Pressure (Volume) can be added or removed. In general, an increase in Pressure (or decrease in Volume) drives the phase change gas⇒liquid⇒solid.

Question 9

Temperature and heat are two different variables measured using different units. Name the units used for temperature. Name the units used for heat.

Answer 9

Temperature is measured in degrees: Kelvin (K), Fahrenheit (°F), Celsius (°C), or Rankine (°R).

Heat is a form of energy often measured in joules (J) or calories (cal).

Question 10

What name is associated with a phase change from

1. solid (ice) to liquid (water)?
2. liquid (water) to solid (ice)?

Answer 10

1. solid⇒liquid is melting (fusion)
2. liquid⇒solid is freezing (solidification)

Question 11

What name is associated with a phase change from

1. gas (water vapor) to liquid (water)?
2. liquid (water) to gas (water vapor)?

Answer 11

1. gas⇒liquid is condensation
2. liquid⇒gas is vaporization (boiling)

Question 12

What name is associated with a phase change from

1. gas (water vapor) to solid (ice)?
2. solid to gas?

Answer 12

1. gas⇒solid is deposition
2. solid⇒gas is sublimation

Question 13

Why are the slopes zero for plateaus A and B?

Answer 13

Zero slope means no temperature change even though the amount of heat added to the system continues to increase. This occurs because any heat input is dedicated to breaking bonds between molecules, instead of increasing temperature.

Question 14

Define and state the use of a:

Phase Diagram

Answer 14

A phase diagram is a graph of the physical states (solid, liquid, gas) of a substance given a range of temperature and pressure

Question 15

Define:

Melting/Freezing Point

Answer 15

The normal melting or freezing point is the temperature a substance changes between solid and liquid phases at standard pressure (1 atm).

Question 16

Define:

Boiling Point

Answer 16

The normal boiling point is the temperature a substance changes from the liquid to gas phase at standard pressure (1 atm).

Question 17

What phase is the substance in sections A, B, and C in the below diagram?

Answer 17

• A represents the Solid phase region.
• B represents the Liquid phase region.
• C represents the Gas phase region.

Question 18

Define:

Standard Temperature and Pressure (STP)

Answer 18

STP is 0º C and 1 atm

Chemistry exams occasionally refer to Standard Ambient Temperature and Pressure (SATP), which you should know is 25ºC and 1 atm.

Question 19

Is heat absorbed or released during a phase change from

1. solid (ice) to liquid (water)?
2. liquid (water) to solid (ice)?

Answer 19

1. solid⇒liquid, heat absorbed (endothermic)
2. liquid⇒solid, heat released (exothermic)

Question 20

Is heat absorbed or released during a phase change from

1. gas (water vapor) to liquid (water)?
2. liquid (water) to gas (water vapor)?

Answer 20

1. gas⇒liquid, heat released (exothermic)
2. liquid⇒gas, heat absorbed (endothermic)

Question 21

Is heat absorbed or released during a phase change from

1. gas (water vapor) to solid (ice)?
2. solid to gas?

Answer 21

1. gas⇒solid, heat released (exothermic)
2. solid⇒gas, heat absorbed (endothermic)