Presentation: Algorithm for a Recipe

Slide 1 of 7 · Settling starter · Design Technology · Year 8

5 minutes

Algorithm for a recipe: Welsh cakes, picau ar y maen

A recipe written in sentences is not an algorithm. An algorithm is a set of steps so clear that somebody who has never made the thing can follow them without guessing. Nothing is heated and nothing is eaten today: the recipe is only the raw material.

While the register is called: write your name, class and date on your worksheet, then read the whole recipe sheet before writing anything. Underline every instruction verb (weigh, rub, stir, roll, cut, cook).

Starter question: How many rounds should the recipe make, and what size cutter does it use?

DCF: Data and computational thinking → Problem-solving and modelling No computers and no cooking

Slide 2 of 7 · Today’s brief and key words · Design Technology · Year 8

3 minutes

Your brief: turn the recipe into an algorithm and a flowchart

You will sort the recipe into inputs, processes and outputs (Part A), write a numbered algorithm with one instruction per line (Part B), draw a flowchart with at least 2 decisions and 1 loop (Part C), and answer 2 trick questions (Part D).

Terminator

A rectangle with rounded ends. Says Start or Stop. Every flowchart has exactly 1 start.

Input / output

A parallelogram. Something going in, like ingredients, or coming out, like the finished cakes.

Process

A plain rectangle. Something being done: rub, stir, roll, cut, cook.

Decision and loop

A diamond with a Yes or No question. An arrow back up to an earlier step is a loop: it repeats work until a condition is met.

DCF: Data and computational thinking → Problem-solving and modelling Both arrows out of a diamond must say Yes and No

Slide 3 of 7 · Part A: inputs, processes, outputs · Design Technology · Year 8

7 minutes

Part A: sort the recipe into inputs, processes and outputs

Fill the 3 columns from the recipe. Then answer the question underneath: the equipment is neither an input nor a process, so what would you call it, and why does an algorithm still have to mention it?

Inputs (what goes in)	Processes (what is done)	Outputs (what comes out)
225 g self-raising flour	Rub butter into flour	12 to 14 cooked Welsh cakes, dusted with caster sugar, on a cooling rack
110 g cubed cold butter	Stir in sugar, currants and spice

Part A on your worksheet · 7 minutes Use the amounts from the recipe, not “some flour”

Supply teacher script (no subject knowledge needed)

Say aloud: “The first 2 rows are on the board. Copy them and finish the table from the recipe. Inputs are things that get used up, processes are things you do, outputs are what comes out at the end. Then answer the equipment question on the 2 lines below.”

Quick check: Inputs: 225 g self-raising flour, 110 g cubed cold butter, 85 g caster sugar, 50 g currants, ½ tsp mixed spice, 1 beaten egg, up to 2 tbsp milk (a conditional input, only used if the dough will not hold together), heat at a medium setting, extra butter and sugar for greasing and dusting. Processes: rub butter into flour; stir in sugar, currants and spice; add egg and mix to a firm dough; add milk a spoonful at a time and re-mix; roll out to 5 mm; cut 6 cm rounds; re-roll the offcuts; grease and heat the bakestone; cook the first side for 2 minutes; look underneath and judge the colour; turn over and cook the second side; move to the rack and dust with sugar. Outputs: 12 to 14 cooked Welsh cakes, plus the information “the underside is golden brown”, which the decision uses.

Equipment answer: it is a resource, a tool the process needs but does not consume or produce (the bowl is still a bowl at the end; the 225 g of flour is gone). The algorithm must still list it because the steps are impossible without it (“cut out rounds” means nothing without a cutter) and because it fixes the numbers: the 6 cm cutter and 5 mm thickness give 12 to 14 cakes, and a bakestone rather than an oven is why they cook in batches on 2 sides.

Slide 4 of 7 · Part B: the numbered algorithm · Design Technology · Year 8

11 minutes

Part B: write the numbered algorithm, one instruction per line

Use the amounts and times from the recipe: “a bit of flour” is not an instruction. No sentences with “and then” in them. Mark any step that repeats with REPEAT and any question with IF.

Model opening:

1. Wash hands.
2. Collect equipment: bowl, wooden spoon, rolling pin, 6 cm cutter, bakestone, fish slice, cooling rack, scales, timer.
3. Weigh 225 g self-raising flour into the bowl.
4. Add 110 g cold cubed butter.
5. Rub the butter into the flour with fingertips until the mixture looks like fine breadcrumbs with no lumps of butter left.

A repeat looks like this: 9. IF the dough is crumbly and will not hold together: REPEAT add 1 tablespoon of milk and mix again UNTIL the dough holds together OR 2 tablespoons have been used.

Part B on your worksheet · 11 minutes Every REPEAT needs an UNTIL that ends it

Supply teacher script (no subject knowledge needed)

Say aloud: “The first 5 lines of a good algorithm are on the board, and an example of how to write a repeat. Carry on from the recipe. One instruction per line, with the real amounts and times. If a step repeats, write REPEAT and say what stops it. If a step asks a question, write IF.”

Quick check: a secure algorithm has about 25 lines and 3 repeats: milk a tablespoon at a time until the dough holds together or 2 tablespoons have been used; re-roll the offcuts and cut again until the dough is used up (expect 12 to 14 rounds); cook each batch of up to 4 rounds until all the rounds are cooked. Inside the cooking batch: cook for 2 minutes, lift the edge and look underneath, IF not golden brown REPEAT cook 30 more seconds and look again UNTIL golden brown, turn over, cook the second side for 2 minutes, move to the rack, dust with caster sugar while warm. It ends with turning off the heat, leaving the bakestone to cool, and STOP.

Walk the room: cross out any line that hides 2 instructions (“roll and cut” can stay only if the pupil treats it as one box later), and ask for numbers wherever a pupil has written “some” or “a while”.

Slide 5 of 7 · Part C: the flowchart · Design Technology · Year 8

16 minutes

Part C: draw the flowchart in the frame

Start at the top with a terminator. Parallelogram for the ingredients going in and the cakes coming out, rectangles for the things you do, diamonds for the questions. Label every arrow out of a diamond Yes or No. You need at least 2 decisions and at least 1 arrow that loops back to an earlier step.

Top of the chart: START → INPUT: 225 g flour, 110 g butter, 85 g sugar, 50 g currants, ½ tsp mixed spice, 1 beaten egg → Rub the butter into the flour with fingertips until like breadcrumbs → Stir in the sugar, the currants and the mixed spice → Add the beaten egg and mix to a firm dough.

Then a diamond: Has the dough come together? No → Add 1 tbsp milk, mix (2 tbsp maximum), arrow back up to the diamond. Yes → carry on to rolling and cutting.

Part C on your worksheet · 16 minutes Use a pencil and a ruler; this is the part that gets marked

Supply teacher script (no subject knowledge needed)

Say aloud: “The top of the flowchart and the first decision are on the board. Draw in pencil in the frame on your sheet. Work down your Part B algorithm: each thing you do is a rectangle, each IF is a diamond, each REPEAT is an arrow going back up. The flowchart is the part your class teacher will mark.”

Quick check: the other diamonds a secure chart contains are “Is all the dough used up?” (No loops back to roll out and cut), “Is the underside golden brown?” (No goes to “Cook for 30 seconds more, then look again” and loops back) and “Are all the rounds cooked?” (No loops back to cooking the next batch). The chart ends OUTPUT: 12 to 14 Welsh cakes, cooked on both sides and dusted with caster sugar → STOP.

Walk the room: the 2 things to look for are both arrows out of every diamond labelled Yes and No, and at least 1 arrow that goes back up the page. Do not show the worked example flowchart until pupils have drawn their own; it is the answer and they will copy it.

Slide 6 of 7 · Part D and self check · Design Technology · Year 8

5 minutes

Part D: the 2 trick questions, then check your own work

Answer both trick questions in the table. Then tick each success criterion you have met and correct 1 thing, for example a diamond with an unlabelled arrow.

I can sort a real process into inputs, processes and outputs, and say why equipment belongs in none of them.
My algorithm has one instruction per line, with real amounts and real times taken from the recipe.
My flowchart uses the right shape for each kind of step, and both arrows out of every decision are labelled Yes and No.
My flowchart contains at least one loop that repeats work until a condition is met.
I can explain why a step that must be repeated until something is true cannot be written as a single process box.

Part D on your worksheet · 5 minutes Finished early? Try the allergen check or the 24-cake version

Supply teacher script (no subject knowledge needed)

Say aloud: “5 minutes for the 2 trick questions in Part D. Then read the success criteria on the board, tick the ones you have met and fix 1 thing on your flowchart.”

Quick check: Milk question: it is not one action, it is an action plus a test, repeated: add a spoonful, mix, look, then stop or go round again. A process box runs once and cannot ask a question, so it needs a process box, a decision after it and an arrow back. It also needs the limit of 2 tablespoons, otherwise the loop could add milk forever (an infinite loop, or a bowl of batter). Colour question: if the diamond came before the cooking box, the first test would happen the moment raw dough hit the bakestone, the answer would always be No, and the loop would cook in 30-second chunks from cold and never do the 2 minutes the recipe asks for. Cook first, test second, and the 2 minutes happens exactly once.

Extension answers: the allergen check (wheat, milk, egg) goes right after START and before any ingredient is used, because once the flour is in the bowl the work is wasted. Doubling to 24 cakes doubles the ingredient amounts but not the 5 mm thickness, the 6 cm cutter, the 2 minutes per side or the heat setting; the trap is the milk, which is still “only if needed, up to a limit”, not simply 4 tablespoons. A machine with no eyes would measure time or temperature instead of colour, for example a fixed total cooking time per side.

Slide 7 of 7 · Plenary review · Design Technology · Year 8

3 minutes

Swap, test, and check before handing in

Swap with a partner. Follow their algorithm word for word and tell them the first place you had to guess. Then check the 3 answers below.

Question	Correct answer
Which shape holds a question, and how must its arrows be labelled?	A diamond (decision), with both arrows labelled Yes and No.
What stops the milk loop from running forever?	The limit of 2 tablespoons, or the dough coming together.
Is the mixing bowl an input, a process or an output?	None of them. It is a resource: needed but not used up or produced.

Check your name and class are on your worksheet Leave recipe sheets neat on the desk