Organizing IdeaMatter — Understandings of the physical world are deepened by investigating matter and energy.
Guiding QuestionHow can the particles of matter be influenced by heating or cooling?
Learning OutcomeStudents investigate how particles of matter behave when heated or cooled and analyze effects on solids, liquids, and gases.
This lesson covers: How a material’s response to temperature change must be considered when designing and constructing infrastructure; the significance of expansion and contraction in the design of sidewalks, bridges, and roads; applying the particle model of matter to real-world engineering problems.
Your job
Real engineers know that materials expand when hot and
contract when cold. If a long bridge has no expansion gaps,
it will buckle and crack on a hot day. But if it has too many
gaps, the road becomes bumpy and expensive to build.
Place expansion joints in the right spots so the structure
survives an entire winter-to-summer cycle without cracking. Click anywhere
on the structure to drop in a joint. Click an existing joint to remove it.
structure
Bridge
joints placed
0
temperature
15°C
Drag to test heat:15°C
How to play
the rules
Click on the structure to add an expansion joint where you click
Click an existing joint to remove it
Press "Run the Test!" to cycle from neutral → freezing → boiling → neutral
If any joint runs out of room (gap reaches 0), the structure cracks — fail!
Pass with the fewest joints possible to earn 3 stars (★★★)
the science behind it
Every segment of the structure tries to grow longer in heat and shrink in cold.
With the bridge ends anchored, that growth has to go somewhere — into the
expansion joints. More joints means each segment is shorter,
so each segment expands less, so each gap doesn't need to be as wide. It's a
balancing act between safety (more joints) and a smooth ride (fewer joints).