States of Matter

1. Complete the following table about the kinetic theory of matter: (4 points)

a ) Distance between particles in SOLIDS:

b ) Distance between particles in LIQUIDS:

c ) Distance between particles in GASES:

d ) Force between particles in SOLIDS:

e ) Force between particles in LIQUIDS:

f ) Force between particles in GASES:

g ) Shape of SOLIDS:

h ) Shape of LIQUIDS:

i ) Shape of GASES:

j ) Volume of SOLIDS:

k ) Volume of LIQUIDS:

l ) Volume of GASES:

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2. Gold has a density of 19 300 kg/m³. Solve the following: (4 points)

a ) Calculate the density of gold in kg/L (1 m³ = 1000 L):

b ) Calculate the volume in liters of 1 ton of gold (1 ton = 1000 kg):

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3. A refrigerator cools its contents by allowing a pressurized refrigerant to expand and thereby cool down. Suppose the gas expands from 2.0 atm and 20°C with a volume of 1.0 L, to a pressure of 1.0 atm and a volume of 1.8 L. Assuming the gas behaves ideally, <strong>calculate its final temperature in °C</strong>: (4 points)

Feedback: Use the combined gas law: \( \frac{P_1 \cdot V_1}{T_1} = \frac{P_2 \cdot V_2}{T_2}\). First convert initial temperature to Kelvin: T₁ = 20 + 273 = 293 K. Then: \(T_2 = \frac{P_2 \cdot V_2 \cdot T_1}{P_1 \cdot V_1} = \frac{1.0 \times 1.8 \times 293}{2.0 \times 1.0} = 263.7\) K. Converting back to Celsius: T₂ = 263.7 - 273 = -9.3°C. The gas cooled down significantly during expansion, which is how refrigerators work!

4. Given the heating curve of this substance, identify the following parts: (5 points)

a ) State of matter in Section 1 (initial rising part):

b ) State of matter in Section 2 (first flat part):

c ) State of matter in Section 3 (middle rising part):

d ) State of matter in Section 4 (second flat part):

e ) State of matter in Section 5 (final rising part):

f ) Which section(s) show phase changes? (write section numbers, e.g., '2 and 4'):

g ) The melting/freezing point is what temperature (in °C)?

h ) The boiling/condensation point is what temperature (in °C)?

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5. Even on a cool day, wet clothes can dry when left outdoors. Which statement best explains why this happens? (1 point)

The water must reach its boiling point to change into vapor The water molecules at the surface gain enough energy from the surroundings to escape into the air, even below the boiling point The water is absorbed by the fabric and disappears The air breaks the water molecules apart chemically

Feedback: This is evaporation - it occurs at any temperature when surface molecules gain enough energy to escape, not just at the boiling point.

6. During condensation, energy is: (1 points)

Absorbed by the substance Released to the surroundings Neither absorbed nor released Converted entirely into motion

Feedback: Condensation is an exothermic process - when gas particles lose energy and form a liquid, energy is released to the surroundings.

7. If the pressure on a gas is reduced to half, and temperature stays constant, what happens to the volume? (1 points)

The volume is halved The volume doubles The volume stays constant The gas cools down

Feedback: According to Boyle's Law \((P_1 \cdot V_1 = P_2 \cdot V_2)\), pressure and volume are inversely proportional at constant temperature. If pressure is halved, volume doubles: \(V_2 = \frac{P_1 \cdot V_1}{P_2} = \frac{P_1 \cdot V_1}{0.5P_1} = 2V_1\)

8. When a gas is heated in a rigid container (constant volume), what happens to the pressure? (1 points)

The pressure increases The pressure decreases The pressure remains constant The gas expands

Feedback: At constant volume, pressure and temperature are directly proportional. As temperature increases, particles move faster and collide more forcefully, increasing pressure.

9. Given a phase diagram of carbon dioxide (CO₂) showing regions for solid, liquid, and gas phases: (2 points)

a ) Minimum pressure (in atm) at which liquid CO₂ can exist:

b ) At 0°C and 1 atm, what is the phase of CO₂?

c ) At 0°C and 100 atm, what is the phase of CO₂?

d ) At 0°C and 1000 atm, what is the phase of CO₂?

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