Intermolecular Forces

When a solid reaches the temperatures of its ___, it can become a liquid.

• melting point
• freezing point
• boiling point
• density

When a liquid reaches the temperatures of its ___, it can become a gas.

• melting point
• freezing point
• boiling point
• density

The weaker the intermolecular forces of a substance the _____________ the boiling point

• higher

• lower

Which substance has the weakest intermolecular forces?

• Substance A, boiling point of 75 °C

• Substance B, boiling point of 105 °C

• Substance C, boiling point of 25 °C

• Substance d, boiling point of 45 °C

Water and ammonia molecules are roughly the same size and the same mass but ammonia boils at -28°F and water boils at 212°F. What can we conclude about the intermolecular forces between water and ammonia?

• Water has stronger intermolecular forces

• Ammonia has stronger intermolecular forces

• The intermolecular forces are the same strength

• Not enough information is given

The melting points and boiling points of substances can lead to inferences about the intermolecular attraction of the atoms of these substances because higher melting and boiling points indicate that

• the atomic mass of the substances is smaller.

• the substances produce exothermic reactions.

• atomic radii increases heat is added.

• more energy is needed to separate molecules.

Students conduct an investigation that compares the boiling points of different substances. The students' data is represented in the table to the left. Based on the data, order the substances from the weakest intermolecular forces to the strongest intermolecular forces

• Acetone

• Water

• Propanol

• Ethanol

Answer explanation

The weaker the intermolecular forces that hold the substance together, the lower the substance's boiling point will be. This means that the substance with the lowest boiling point has the weakest intermolecular forces and the substance with the highest boiling point has the strongest intermolecular forces. Acetone has the lowest boiling point followed by ethanol then propanol with water having the highest boiling point, which means that acetone has the weakest intermolecular forces followed by ethanol then propanol with water having the strongest intermolecular forces.