London Bridge on a Hot Summer Day
45 Minute Lesson
NJ Standards
5.2.4.E.1 / 5.2.2.E.2 – Identify the force that accelerates an object.
5.2.2.B.1 – Some properties of matter can change as a result of heating or cooling.
5.1.12.D.2 – Science involves using language, both oral and written, as a tool for making thinking public.
5.1.12.D.1 – Science involves practicing productive social interactions with peers, such as partner talk, whole-group discussions, and small group
work.
NJ Standard
5.2.4.E.1
5.2.2.E.2
Goal
Students will understand how a bridge works structurally.
5.1.12.D.1
5.1.12.D.2
5.2.2.B.1
Students will understand how objects change in different temperatures.
Resources
Student Use: Gum Drops, Toothpicks, Glue, Tape, Paper, Spaghetti, Paper Clips
Teacher Use: Paper Clips, Styrofoam Cup, Many pennies
Pre-Requisite Knowledge

Dynamics, Newton's Laws of Motion

Kinetic Molecular Theory
Evidence
Students will use their knowledge of forces to
build a rudimentary wood bridge capable of
carrying a load of 15 pennies.
Students will be able to make a prediction in
regards to what will happen to their bridge in
varying temperatures, using a microscopic
model of matter.
Real World Applications

Thermal Expansion; Why are there small gaps on bridge connectors?
Why does one heat the lid of a tight jar when attempting to open it?

Bridges; Why are bridges shaped the way they are? And how can they support so much?

Bridge Destruction; Buckling. Why do perfectly good structures all of a sudden fail and break?
Potential Difficulties

Students may have difficulties building strong supports without analysis of forces and torques.

Students may have difficulties predicting the behavior of materials in different temperatures without a strong understanding of the
kinetic molecular theory.

Students may have difficulties justifying the use of pre-existing support structures.

Students may have difficulty in choosing an adhesive material and justifying one over the other.
Lesson Description
A. Opening (5 minutes)
Opening question: What elements go into making a bridge? Students will view a picture of a bridge connector with a gap. Why do bridges
have this gap? Students will brainstorm why there is a noticeable gap on a bridge connector.
[Students should easily come up with the reliability and consistency of a strong structure. Some students may identify strong materials
that can withstand different climates. Students may also note the use of cables.
Stress the fact that the bridge is not completely connected to the non-bridge area. Why is there a noticeable gap? Wouldn't this be a
safety hazard?]
B. Building a Bridge (15 minutes)
Students in small groups will construct open bridge structures, 20 inches in length that can carry a load of minimum 15 pennies (in
addition to the styrofoam cup supporting said pennies) .
Students are permitted to use only three materials out of the following:
Gum drops, Tape, Glue, Toothpicks, Spaghetti, Paper, Paper Clips
Groups should document the reason they choose each material and the particular reason as to why their bridge is shaped the way it is.
[Students may take inspiration from pre-existing bridge structures and or truss designs. Students may determine one adhesive to be
better than the other if not use multiple adhesives.]
C. Testing the bridge (5 minutes)
Groups will test their bridges over a 18-inch gap with a styrofoam cup attached to the bridge. The goal is to be able to support 15 pennies
without the bridge showing any visible buckling or deterioration.
D. Why This or The Other? (15 minutes)
Groups will have a brief discussion on their design and material choices. Students will be given a new challenge, can their bridge hold up
under a cold rainy day? Groups should also make predictions on how their bridge may be affected by the hot weather. Which of the
materials are good for withstanding cold and hot weather? Based on your ideas of how the adhesives behave in higher temperatures
have students discuss again why there are small gaps between bridge connectors. Stress to students what happens to an object when it
becomes hot.
[Hot weather:
Bridges made of glue may see the adhesive melt, proving catastrophic
Bridges connected with gum drops will become sticky. Is this a concern?
Bridges connected with paper, spaghetti, tape will curl or unfold if they are designed to be supports.
Cold, Rainy Weather:
Glue and gum drop bridges harden and may crack. Paper, spaghetti, paper clips and tape may show no signs of effects. Metal and wood
tend to have no visible signs of wear compared to adhesives.
Students can benefit from a real life example of heating a tight lid in an attempt to open it, in order to understand thermal expansion.]
E. Reflection (5 minutes)
Students reflect on what they have learned. What have they learned about building bridges, materials used, bridge design?
Time Table
Activity
A – Opening
Time Duration (Clock)
5 minutes
(0:05)
Students doing
Discussion
B – Building Bridges
15 minutes
(0:20)
C – Testing Bridges
D – Why Choose That or the Other?
E – Reflection
5 minutes
15 minutes
5 minutes
(0:25)
(0:40)
(0:45)
Building bridges, keeping notes on
design choices
Testing bridges
Class discussion
Reflect
Teacher doing
Discussion, present materials for
(B)
Observing
Observing
Discussion, Listening
Discussion, Listening
Formative Assessment
Why do we build bridges with triangle like structures? Why not a flat
road just like the road atop a bridge?
Trusses (triangular like structures) have very good support compared to
flat line or square structures. Exploring the structure with a force
diagram is useful here.
What happens to objects as they are heated?
Certain objects may change physical states. But students here should
recognize that heating objects increases the kinetic energy of atoms in
the object. This increases the volume an object takes up (thermal
expansion). Dramatic increases in volumes are seen in phase changes.
Why is _____________ a good/bad material to use in constructing our Students will notice that metal and wood do not show very visible signs
of change in different temperatures. However, different materials have
model bridge?
varying advantages and disadvantages to be taken into consideration.