Opening

GROW · SCIENCE · Lesson 3 of 11

Design a removable spill-mat insert

Learning intention

Plan a fair material comparison, record water-retention results and justify a product choice.

Brief: retain at least 6 g of water in every trial.

Choose the lowest-cost product that meets the brief.

A good decision needs a fair comparison.

Success looks like

Name the changed factor, measured outcome and at least two controls.
Record wet and dry mass, then calculate retained water with units.
Choose a product using the stated requirement and acknowledge a test limitation.

Retrieval

GROW · SCIENCE · Lesson 3 of 11

Connect properties to a purpose

R1. What does absorbent mean?

R2. Which must stay the same: soak time or product type?

R3. Is a heavy wet cloth necessarily holding more water?

I do

GROW · SCIENCE · Lesson 3 of 11

What are we actually testing?

Absorbent structures take water in.

Our measure is water held after a fixed drip time.

Water sitting on a surface is not the same thing.

Water can enter connected spaces

Diagram description

A simplified close-up compares a fibrous absorbent sample, with spaces that hold water, and an intact plastic sheet with a drop remaining on its surface. Dots are enlarged water regions, not single molecules.

I do

GROW · SCIENCE · Lesson 3 of 11

Subtract the starting mass

Constructed example: dry sample 2.0 g.

Wet sample after dripping: 9.0 g.

Retained water: 9.0 − 2.0 = 7.0 g.

Measure water retained, not total wet mass

Diagram description

Original worked example with constructed masses: dry sample 2.0 g and wet sample 9.0 g after a fixed dripping time, so retained water is 7.0 g. No real measurements are claimed.

Continue within this stage’s shared time.

I do

GROW · SCIENCE · Lesson 3 of 11

Keep the question and method matched

Change the product; measure retained water.

Keep area, layers, soak time and drip time the same.

Use fresh dry samples for three trials.

Make the comparison answer one question

Diagram description

Three connected stages of a controlled sample test: dry mass and sample area, soak for 30 seconds, then drip vertically 10 seconds without squeezing and measure wet mass. These settings define this original comparison.

Continue within this stage’s shared time.

We do

GROW · SCIENCE · Lesson 3 of 11

Rescue this unfair test plan

“Large felt: soak 60 s, squeeze hard.”

“Small paper: soak 10 s, weigh immediately.”

Use page 1 to find and repair the unfair changes.

My response — say it, sketch on paper or type

We do

GROW · SCIENCE · Lesson 3 of 11

Read a repeat, not a promise

Constructed sample data: retained water after the fixed method.

The requirement is at least 6 g on every trial.

Which products meet it in these three trials?

Constructed sample results; one-layer 10 cm squares; fresh dry samples.
Product	Trial 1 / g	Trial 2 / g	Trial 3 / g
Kitchen paper	5.2	5.5	5.3
Cotton cloth	7.0	6.8	7.2
Felt sheet	8.0	7.8	8.2

My response — say it, sketch on paper or type

Continue within this stage’s shared time.

We do

GROW · SCIENCE · Lesson 3 of 11

Best for which job?

Fictional costs per square: paper 2, cotton 4, felt 6 credits.

The brief asks for the lowest cost that passes every trial.

Choose and defend; then name one untested property.

My response — say it, sketch on paper or type

Continue within this stage’s shared time.

Hinge

GROW · SCIENCE · Lesson 3 of 11

What makes the comparison fair?

Which plan can answer which product retains more water?

You do

GROW · SCIENCE · Lesson 3 of 11

Write the product team’s report

Choose one route, with the common evidence page.

Plan the comparison and record retained water.

Recommend a product using the exact brief.

My response — say it, sketch on paper or type

You do

GROW · SCIENCE · Lesson 3 of 11

Record the result you have

Retained water = wet mass − dry mass.

Keep the unit g with each result.

Actual practical result? Record it honestly and separately.

My response — say it, sketch on paper or type

Continue within this stage’s shared time.

You do

GROW · SCIENCE · Lesson 3 of 11

Keep the conclusion within the evidence

Does the product pass every trial?

Is it the cheapest product that passes?

Which feature of a real mat still needs testing?

My response — say it, sketch on paper or type

Continue within this stage’s shared time.

Review

GROW · SCIENCE · Lesson 3 of 11

Challenge the design decision

One pupil recommends felt because it holds the most.

Another recommends cotton because it meets the cheaper brief.

Which claim answers our actual question?

My response — say it, sketch on paper or type

Review

GROW · SCIENCE · Lesson 3 of 11

Plan our next improvement

Which untested property should the team investigate?

Suggest a measurable outcome and one control.

Teacher: explain how one suggestion will shape the next test.

My response — say it, sketch on paper or type

Continue within this stage’s shared time.

Exit

GROW · SCIENCE · Lesson 3 of 11

Exit: the fair-test check

E1. Name what changes and what is measured.

E2. Name two conditions that stay the same.

E3. Recommend a product using one result and the brief.

My response — say it, sketch on paper or type

My science task sheets

Choose one route with your teacher. Shared evidence and the exit sheet appear in every route. Your work stays here while the page is open; save it before closing.

1 • Shared brief and evidence

Fictional design brief and constructed sample data. Compare these particular one-layer 10 cm × 10 cm product squares, not every possible material.

Brief: a removable spill-mat insert must retain at least 6 g of water in every trial. Choose the lowest-cost tested product that meets this. Fictional costs per square: kitchen paper 2 credits; cotton 4 credits; felt 6 credits.

Fixed test method

Dry and tare the weighing tray before each measurement. Weigh a fresh dry sample. Immerse 30 s. Drip vertically 10 s without squeezing. Weigh wet promptly. Retained water = wet − dry mass.

Keep conditions matched

Same area, one layer, water conditions, immersion, timing, weighing tray and scale. Use three fresh dry samples per product.

Plan needing repair

Large felt: soak 60 s and squeeze hard. Small paper: soak 10 s and weigh immediately. No dry mass recorded.

Product	Dry mass each / g	Wet masses T1 / T2 / T3 / g
Kitchen paper	0.8	6.0 / 6.3 / 6.1
Cotton cloth	2.0	9.0 / 8.8 / 9.2
Felt sheet	2.5	10.5 / 10.3 / 10.7

Constructed sample data above: sample thicknesses and structures differ; this compares the named products at equal area, not intrinsic absorption at equal thickness.

W1. Repair at least two parts of the unfair plan. W2. Which products meet the brief? Which is cheapest?

2 • Supported route: fair test to design choice

Use page 1. Read, point, draw or dictate. A calculator is welcome.

S1. What do we deliberately change? Product type Soak time for each product

S2. What do we measure? Retained water mass in g Which colour looks best

S3. Name two things to keep the same. Word bank: sample area / soak time / final result / drip time.

Product	Wet mass T1 / g	Dry mass / g
Paper	6.0	0.8
Cotton	9.0	2.0
Felt	10.5	2.5

S4. Constructed data from page 1. Complete: wet − dry. Show or dictate one subtraction.

Constructed repeat summary: paper holds 5.2, 5.5, 5.3 g; cotton 7.0, 6.8, 7.2 g; felt 8.0, 7.8, 8.2 g. Every trial must reach 6 g. Costs: paper 2, cotton 4, felt 6 credits.

S5. I choose ____ because all trials reach ____ g or more, and it costs less than ____ .

3 • Standard route: a fair comparison report

Use the constructed measurements on page 1. Your conclusion should answer the product brief.

N1. State the factor you change, the outcome you measure and three conditions you keep the same.N2. Write the key measurement steps, including the dry start, soak time, drip time and repeats.

Product	Water T1 / g	Water T2 / g	Water T3 / g
Paper
Cotton
Felt

N3. Calculate and record water retained from the constructed wet and dry masses on page 1. Show one subtraction.

3 continued • Standard route: the design decision

Use your calculations and the common evidence page. Explain the decision and the next useful test.

N4. Recommend the cheapest passing product. Quote its lowest trial result and compare the cost with the other passing product.N5. State one reason this does not prove a material is best for every mat, and one next test.

4 • Stretch route: test the rule as well as the sample

Use the constructed sample data and fictional cost brief on page 1.

T1. Calculate retained water for all nine samples. Calculate the mean for each product, showing one calculation. A calculator is welcome.T2. Why is the mean alone not enough for our every-trial requirement? Use this extra constructed set: 5.0, 7.0, 9.0 g.T3. Recommend the lowest-cost passing product from page 1. State one uncertainty and a practical improvement.T4. Our squares have equal area but different dry masses and thicknesses. What question did our test answer? How would a comparison of water retained per gram of product answer a different question?T5. Propose a second measurable property for a reusable mat. Give a fair comparison method with two controls.

5 • Exit and optional practical record

Choose the correct label: paper evidence route / actual practical results. Do not present constructed values as your own measurements.

E1. What changes, and what is measured in this comparison?E2. Name two important controls and explain one.E3. Recommend a product using the exact brief and a numerical result.

Optional actual product:	Dry / g	Wet / g	Retained / g
Trial 1
Trial 2
Trial 3

E4. Record a test problem or one useful improvement. How would it improve the evidence?Reflection. One choice I can now defend with evidence is …