Unit 5 Review

Which of the following is a phase change from liquid to gas?

• Melting

• Freezing

• Boiling

• Condensation

Answer explanation

Boiling is the phase change from liquid to gas, occurring when a liquid reaches its boiling point. Melting and freezing refer to solid and liquid changes, while condensation is the change from gas to liquid.

Tags

NGSS.MS-PS1-4

Which intermolecular force is present between water molecules due to the presence of hydrogen bonded to oxygen?

• London dispersion forces

• Dipole-dipole forces

• Hydrogen bonding

• Ionic bonding

Answer explanation

The correct choice is hydrogen bonding, which occurs between water molecules due to the attraction between the hydrogen atom of one water molecule and the oxygen atom of another, resulting in strong intermolecular forces.

Tags

NGSS.HS-PS2-6

According to the kinetic molecular theory, what happens to the average kinetic energy of gas particles as temperature increases?

• It decreases

• It remains the same

• It increases

• It becomes zero

Answer explanation

According to the kinetic molecular theory, as temperature increases, the average kinetic energy of gas particles also increases. This is because temperature is directly related to the energy of the particles.

What is the boiling point of water at standard atmospheric pressure?

• 0°C

• 50°C

• 100°C

• 212°C

Answer explanation

The boiling point of water at standard atmospheric pressure is 100°C. This is a well-established scientific fact, as water transitions from liquid to gas at this temperature under normal conditions.

Tags

NGSS.MS-PS1-4

Which of the following best describes a dipole-dipole force?

• Attraction between nonpolar molecules

• Attraction between ions and polar molecules

• Attraction between polar molecules

• Attraction between electrons and nuclei

Answer explanation

Dipole-dipole forces occur due to the attraction between the positive end of one polar molecule and the negative end of another polar molecule, making 'Attraction between polar molecules' the correct choice.

What is the heat of fusion?

• The energy required to vaporize a liquid

• The energy required to melt a solid

• The energy released during condensation

• The energy required to freeze a liquid

Answer explanation

The heat of fusion is the energy required to melt a solid into a liquid. This process involves breaking the bonds that hold the solid structure together, allowing it to transition into a liquid state.

Tags

NGSS.HS-PS3-4

A sample of gas has a volume of 2.0 L at a pressure of 1.0 atm. What will the volume be if the pressure is increased to 2.0 atm at constant temperature?

• 1.0 L

• 2.0 L

• 4.0 L

• 0.5 L

Answer explanation

According to Boyle's Law, P1V1 = P2V2. Here, (1.0 atm)(2.0 L) = (2.0 atm)(V2). Solving for V2 gives V2 = 1.0 L. Thus, the volume at 2.0 atm is 1.0 L.

If a gas occupies 3.0 L at 300 K, what volume will it occupy at 600 K at constant pressure?

• 1.5 L

• 3.0 L

• 6.0 L

• 9.0 L

Answer explanation

According to Charles's Law, V1/T1 = V2/T2. Here, V1 = 3.0 L, T1 = 300 K, T2 = 600 K. Solving for V2 gives V2 = (3.0 L * 600 K) / 300 K = 6.0 L. Thus, the gas will occupy 6.0 L at 600 K.

• 2.0 atm

• 4.0 atm

• 9.84 atm

• 19.7 atm

Answer explanation

Using the ideal gas law, PV = nRT, we can calculate pressure (P). Here, n = 2.0 moles, V = 5.0 L, R = 0.0821 L·atm/(mol·K), and T = 27C = 300K. Thus, P = (2.0 * 0.0821 * 300) / 5.0 = 4.0 atm.

A gas sample has a volume of 500 mL at a pressure of 760 mmHg. What will the pressure be if the volume is compressed to 250 mL at constant temperature?

• 380 mmHg

• 760 mmHg

• 1520 mmHg

• 500 mmHg

Answer explanation

Using Boyle's Law (P1V1 = P2V2), we have P1 = 760 mmHg, V1 = 500 mL, and V2 = 250 mL. Solving for P2 gives P2 = (760 mmHg * 500 mL) / 250 mL = 1520 mmHg. Thus, the pressure will be 1520 mmHg.