Monday
Monday: Define the Problem
Rocket is already stacking cups when Raven arrives at the Bench. "Insulated cup," he says. "Three layers. Done."
"Done with what?" Raven asks. "What does it need to do? How will we know it worked?"
Rocket stops. "Keep water warm."
"How warm, for how long, measured how?" Raven taps the Bench Log. "What do you notice? You built before you asked."
Nova hovers over the stack. "Engineers write the finish line first," she says. "Then they build toward it."
Rocket uncaps a pen. "Criteria: warm water drops less than a plain cup after ten minutes. Constraints: Bench materials only."
"Now you are designing," Raven says. "Now build."
Criteria and constraints
A design problem has two parts. Criteria are the goals the solution must meet. Constraints are the limits it must stay inside.
Science standards say the more precisely a design task's criteria and constraints are defined, the more likely the solution will succeed.
Constraints include scientific principles. Heat always moves from the warmer object to the cooler one, so no cup can make warm water warmer by itself.
Good criteria can be measured. "Keeps water warm" is a wish. "Drops fewer degrees in ten minutes than a plain cup" is a criterion.
Three devices to choose from
This week you choose one device and carry it through the whole design cycle.
The insulated cup slows heat leaving warm water. The cold pack uses a kitchen reaction that can absorb heat. The fizzing boat uses the gas a reaction makes to push itself across water.
The standard behind this week asks you to build, test and improve a device that releases or absorbs heat through chemical processes. The cup is the physical version of the same idea: controlling where heat goes.
| Device | What it must do (criteria) | Limits (constraints) | What you measure |
|---|---|---|---|
| Insulated cup | Warm water drops fewer degrees in 10 minutes than a plain cup | Bench materials only, fits on the Bench, built in 20 minutes | Temperature at start and after 10 minutes |
| Cold pack | Temperature drops as far and as fast as possible, in a bag you can hold | Only vinegar or lemon juice and baking soda, never sealed, one quarter cup of liquid | Temperature change and time to the lowest reading |
| Fizzing boat | Travels as far as possible across a pan of water | Only vinegar and baking soda, open container, must float on its own | Distance traveled and time moving |
- Read the question.
- Tap your answer.
| Statement | True or false? |
|---|---|
| Precise criteria and constraints make success more likely. | ? |
| A constraint is a goal the design must reach. | ? |
| Scientific principles can be constraints on a design. | ? |
| Engineers build first and define the problem later. | ? |
- ?Sketch the first prototype.
- ?Write the criteria as measurements.
- ?Name the device you will build.
- ?Write the constraints, including the science that limits you.
Under it, write two criteria you can measure and three constraints. Use the table as a model, then make them your own.
For the insulated cup, a grown-up pours warm tap water. Nothing hotter than tap water is used. Fizzing mixtures are never sealed.
The engineering facts come from the Next Generation Science Standards site, nextgenscience.org, and chemistry texts on chem.libretexts.org.
The problem is defined. Tomorrow you plan the test and the science behind each device before anything gets built.