HS-PS3-1: Modeling Energy Changes in a System
Also called NGSS HS-PS3-1 · Topic: Energy · Physical Science
The Official Wording
Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known.
Clarification statement: Emphasis is on explaining the meaning of mathematical expressions used in the model.
Assessment boundary: Assessment is limited to basic algebraic expressions or computations; to systems of two or three components; and to thermal energy, kinetic energy, and/or the energies in gravitational, magnetic, or electric fields.
NGSS Lead States, 2013 · Read it on nextgenscience.org · checked October 15, 2026
What HS-PS3-1 Means in Plain English
Students build a simple computer model, often a spreadsheet, that tracks energy through a system. When they know how much energy most parts gain or lose and how much leaves or enters, the model works out the change in the one remaining part.
The math stays at basic algebra, with two or three parts and only motion, thermal, gravitational, electric or magnetic energy. Students explain what each formula means. It builds on MS-PS3-5 and supports the thermal energy tests in HS-PS3-4.
HS-PS3-1 I Can Statements
- I can track every joule of energy in a simple system.
- I can calculate one part's energy change from the others.
- I can explain what each term in my energy model means.
HS-PS3-1 Worked Example
A spreadsheet model for a dynamics cart rolling down a tilted track.
A 0.50 kg dynamics cart starts at rest on a track raised 0.50 m at one end. Friction turns 0.20 J into thermal energy on the way down. How much kinetic energy does the cart have at the bottom, and how fast is it going?
- Set up the system: the cart and Earth, with friction carrying some energy out as heat.Energy at top = kinetic energy at bottom + heat
- In one cell, find the stored energy: mass × g × height.0.50 × 9.8 × 0.50 = 2.45 J
- In the next cell, subtract the energy friction turns into heat.2.45 J − 0.20 J = 2.25 J of kinetic energy
- Solve KE = ½mv² for speed in a third cell.v = √(2 × 2.25 ÷ 0.50) = √9 = 3.0 m/s
- Change the height cell to 0.25 m and let the model update.1.225 J − 0.20 J ≈ 1.03 J, so v ≈ 2.0 m/s
Check it: Add it back: 2.25 J of motion plus 0.20 J of heat equals the 2.45 J stored at the top, so no energy is missing.
Common Mistakes with HS-PS3-1
Leaving out energy that leaves the system
“The cart should have all 2.45 J at the bottom.”
Try this: List every place energy goes, including heat from friction, and check that the totals balance before and after.
Forgetting the square on speed
Using KE = ½mv and getting 9 m/s
Try this: Kinetic energy grows with speed squared, so solve with a square root, then check that ½mv² gives the energy back.
Numbers with no meaning
A cell that says =A2*9.8*B2 with no label
Try this: Label each cell with what it stands for, like stored energy at the top, so anyone can read the model.
Where HS-PS3-1 Fits
Practice HS-PS3-1
Quick Check
- A ball has 10 J of stored energy at the top of a ramp and loses 2 J to friction. How much kinetic energy does it have at the bottom?
- Why does a spreadsheet help with energy problems?
- What does mgh stand for in an energy model?