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Cells and Systems 6-8 / Week 12 / Monday
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Week 12 · Design a Growing Station

Monday

Define the problem
// Criteria, constraints and the Cells and Systems report
⏱ about 20 min

Monday: Define the Problem

Rocket arrives at the Windowsill carrying an empty cardboard box, a roll of foil and a big grin.

"The sprouts lean toward the window every day," he says. "I am going to build them a sun palace."

Raven holds up a hand. "Before you build, say what the palace has to do. What do you notice about engineers?"

"They plan first," Rocket sighs. "Fine. It has to make the sprouts grow taller, greener and straighter."

Nova hovers over the box. "Good. Now say what it is not allowed to do," she says.

"Take up the whole sill. Use anything we do not already have. Need any light but the window." Rocket pauses. "That is a lot of rules."

"Those rules are the design problem," Raven says. "Write them down."

Rocket, Raven and Nova with a homemade windowsill growing station. A cardboard box, cut open on one side and lined with shiny foil as a reflector, holds small jars of green sprouts. A ruler is propped beside it. Rocket adjusts the foil, Raven holds up her notebook proudly, and Nova hovers above with a cyan glow in bright window light.

Criteria and constraints

Engineers start by defining a design problem. A design problem includes multiple criteria and constraints, including scientific knowledge that may limit possible solutions.

Criteria are what a successful solution must do. Constraints are the limits it must stay inside.

The more precisely a design task's criteria and constraints are defined, the more likely the designed solution will succeed.

Your design problem: build a windowsill growing station that helps the course sprouts grow better than a plain jar.

Criteria (what it must do)Constraints (limits it must respect)
Sprouts gain more height than in the plain jarFits in a space the size of a shoebox
Leaves stay greenUses only materials already at home
Stems stand upright instead of leaningUses window light only, no lamps
Easy to measure every dayTested for one week against the plain jar
CRITERION OR CONSTRAINT?
  • Read the question.
  • Tap your answer.
"The station may use only window light." Is that a criterion or a constraint?
"The sprouts' leaves must stay green." Criterion or constraint?
"The station must fit in a shoebox-sized space." Criterion or constraint?
What a successful design must do are its ____.
The limits a design must respect are its ____.

Why science belongs in the constraints

Defining constraints includes thinking about scientific principles and other knowledge that are likely to limit possible solutions.

You already know the science. Photosynthesis needs sunlight, carbon dioxide and water. Seedlings bend toward light. Growth depends on light, water, space and the kind of seed.

So a station cannot make sprouts grow without light or water, and it cannot turn a lentil into a bean plant.

Precise criteria and constraints are not rules for the sake of rules. They point you at designs that can actually work.

StatementTrue or false?
Criteria describe what a successful design must do.?
Constraints are limits such as space, materials and time.?
Scientific knowledge can limit which designs are possible.?
A precise design problem makes success less likely.?
WHY THIS EXERCISEThis is the engineering standard for the week in four lines.
Try it
Measure the space on your sill or table where the station will sit. Write the length and width in centimeters.
Gather what you may use: a cardboard box, foil, dark paper, tape, string, a small mirror, extra jars or cups.
Write your own design problem in your Windowsill Log, with at least three criteria and three constraints.
For a grown-up
This week your student builds a growing station from household materials and tests it against a plain jar for a week.
A grown-up does any cutting of cardboard. Mirrors and foil are never used to aim sunlight at anyone's eyes.
The engineering wording comes from the Next Generation Science Standards page for MS-ETS1 at nextgenscience.org.
Draw the empty space your station must fit in, with its measurements. Draw the plain jar beside it.

Good planning. Tomorrow you use the science you know to sketch two possible designs.