MS-PS1-4: Particle Motion, Heat and Changes of State
Also called NGSS MS-PS1-4 · Topic: Structure and Properties of Matter · Physical Science
The Official Wording
Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
Clarification statement: Emphasis is on qualitative molecular-level models of solids, liquids, and gases to show that adding or removing thermal energy increases or decreases kinetic energy of the particles until a change of state occurs. Examples of models could include drawing and diagrams. Examples of particles could include molecules or inert atoms. Examples of pure substances could include water, carbon dioxide, and helium.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What MS-PS1-4 Means in Plain English
Middle schoolers draw particle models that predict what happens when a pure substance gains or loses thermal energy. Particles speed up as it warms and slow down as it cools, and at the melting or boiling point the energy goes into changing state instead.
Models stay qualitative: drawings and diagrams, with no equations for heat. This builds on 5-PS1-1, which pictures matter as tiny particles, and on MS-PS1-1, and leads to MS-PS3-4, where students test how mass and material affect temperature change.
MS-PS1-4 I Can Statements
- I can draw how particles move in a solid, liquid and gas.
- I can predict how heating or cooling changes particle speed.
- I can explain why temperature holds steady while ice melts.
MS-PS1-4 Worked Example
A heating curve a class can record in one period with a hot plate and a beaker of crushed ice.
What happens to the temperature of ice while it melts on a hot plate?
Set It Up: A beaker of crushed ice, a hot plate on low, a thermometer, a stirring rod and a stopwatch.
- Read the starting temperature of the crushed ice.Below freezing, about -5 °C
- Heat on low, stir gently, and record the temperature every 30 seconds.Rises quickly to 0 °C
- Keep recording while the ice melts.Holds near 0 °C for several minutes
- Once the last ice is gone, keep going for five more minutes.Climbs again, past 20 °C
- Graph temperature against time and sketch the particles at each stage.Rise, plateau, rise
The temperature rose to 0 °C, held there while the ice melted, then rose again once only liquid water was left.
Why it works: During melting the added energy frees particles from their fixed places instead of speeding them up, so the temperature holds until all the ice has melted.
Common Mistakes with MS-PS1-4
Expecting the temperature to keep rising during melting
A straight upward line on the predicted graph
Try this: While ice and water are both present, the energy goes into melting, so the temperature stays at 0 °C until the ice is gone.
Particles that grow or shrink
“The particles get bigger when they are heated.”
Try this: Particles stay the same size. Heating makes them move faster and spread apart, which is why most materials expand.
Thinking cold is something added
“The freezer puts cold into the water.”
Try this: Cooling means removing thermal energy. The freezer carries energy away, so particles slow down until they lock into a solid.
Where MS-PS1-4 Fits
Practice MS-PS1-4
Quick Check
- What happens to water particles when ice warms from -10 °C to -2 °C?
- Why does boiling water stay near 100 °C at sea level even on high heat?
- How do particles in a gas differ from particles in a liquid?