Intermolecular Forces Investigation

HS-PS1-3: Bulk Properties and Electrical Forces

Investigate the bulk properties of different substances (like boiling point and surface tension) to gather evidence and infer the relative strength of electrical forces between their particles.

Substance Selection

Substance A

e.g., Methane (CH₄)

Substance B

e.g., Acetone (C₃H₆O)

Substance C

e.g., Water (H₂O)

Investigation

Heat Energy Input (Temperature)

0°C 20°C 100°C

Guide

Observe how heating affects the bulk liquid. Note the temperature at which the substance boils (particles separate entirely). Also observe the shape of the droplet on a flat surface.

Boiling Point Investigation

Current Temp

20°C

Surface Tension (Droplet Shape)

Low Surface Tension

Vapor Pressure Curve

Inferred Properties

Boiling Point	-161°C
Relative IMF Strength	Weak
Dominant Force Type	London Dispersion

Explanation: Substance A has weak intermolecular forces (London Dispersion). Little energy is required to overcome these attractive forces and separate the particles, resulting in a very low boiling point and weak surface tension (flatter droplet).