HS-PS1-3: Inferring Particle Attractions from Bulk Properties
Also called NGSS HS-PS1-3 · Topic: Structure and Properties of Matter · Physical Science
The Official Wording
Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.
Clarification statement: Emphasis is on understanding the strengths of forces between particles, not on naming specific intermolecular forces (such as dipole-dipole). Examples of particles could include ions, atoms, molecules, and networked materials (such as graphite). Examples of bulk properties of substances could include the melting point and boiling point, vapor pressure, and surface tension.
Assessment boundary: Assessment does not include Raoult’s law calculations of vapor pressure.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What HS-PS1-3 Means in Plain English
High school students design and run tests that compare measurable properties of substances, such as how fast a liquid evaporates, its boiling point or its surface tension. From those results they reason about how strongly the particles inside each substance attract one another.
The goal is ranking attractions as stronger or weaker, not naming each type of intermolecular force, and no vapor pressure formulas are required. It builds on states of matter in middle school (MS-PS1-4) and on bond predictions from HS-PS1-1.
HS-PS1-3 I Can Statements
- I can plan a fair test comparing a property of several substances.
- I can rank how strongly particles attract using my evidence.
- I can explain why stronger attractions mean slower evaporation.
HS-PS1-3 Worked Example
An evaporation race a class can run in one period with three clear liquids and a stopwatch.
Which liquid has the weakest attractions between its particles: water, isopropyl alcohol or acetone?
Set It Up: Three dropper bottles, three clean glass slides, a wall clock with a second hand, and eye protection, in a room without drafts or heaters.
- Place one drop of each liquid on its own glass slide at the same moment.Same drop size, same start time
- Time how long each drop takes to disappear completely.Acetone about 1 min, isopropyl about 4 min, water over 15 min
- Repeat with fresh slides two more times and average the times.Three trials per liquid
- Look up each boiling point and compare it with the ranking.Acetone 56 °C, isopropyl 82 °C, water 100 °C
Acetone vanished fastest and water slowest, and the boiling points ranked the liquids in the same order.
Why it works: Particles that attract each other weakly need less energy to break free into the air, so the liquid evaporates sooner and boils at a lower temperature.
Common Mistakes with HS-PS1-3
Thinking boiling breaks molecules apart
“Water boils because the bonds between H and O snap.”
Try this: Boiling separates whole molecules from each other. The bonds inside each water molecule stay intact, and steam is still H₂O.
Changing several conditions at once
One drop on a sunny sill, another under the fan
Try this: Keep drop size, surface, airflow and temperature the same for every liquid so the only difference is the substance itself.
Equating heavier with stronger attraction
“Acetone is a bigger molecule than water, so it should stick together more.”
Try this: Size alone does not decide it. Water molecules attract unusually strongly because of their shape and charge, which outweighs acetone's larger mass.
Where HS-PS1-3 Fits
Practice HS-PS1-3
Quick Check
- Liquid A boils at 35 °C and liquid B at 120 °C. Which has stronger attractions between particles?
- Why does a drop of water bead up more on a slide than a drop of acetone?
- Why run three trials for each liquid?