Open, closed, and isolated systems — and why mass is always conserved
Part 1 · Interactive Model
The Reaction Chamber
Pick a process, then set the container's boundary. Watch what crosses the wall. The scale shows what you'd measure. The matter counter shows every particle that still exists — even the ones that floated away.
Boundary
Matter can cross?
Energy can cross?
Part 2 · Predict Before Reveal
Call the Scale
Read the setup. Decide what the scale reading does before you see the answer. Then lock it in.
Score: 0 / 0
Part 3 · Step-by-Step Machines
Three Reasoning Machines
Enter a weigh-before mass and pick what happens. The auditor traces every gram across the boundary.
Pick a real setup. The classifier reasons through matter and energy, one wall at a time.
Follow one substance and see where it goes when the process runs.
Part 4 · Ten-Question Quiz
Prove It
Question 1 of 10 · Score: 0
Word Box
System
The specific part of the universe you choose to study — here, whatever is inside the container.
Boundary
The wall that separates the system from its surroundings; it decides what can cross.
Open system
Both matter and energy can cross the boundary. An uncovered cup is open.
Closed system
Energy can cross, but matter cannot. A sealed bottle is closed.
Isolated system
Neither matter nor energy can cross. A perfect vacuum thermos is close to isolated.
Conservation of mass
In any process, the total mass of all matter stays the same; atoms are only rearranged.
Surroundings
Everything outside the system that matter or energy can move into or out of.
Gas exchange
When a gas leaves or enters across an open boundary — the usual reason a scale reading changes.