Justifying Material and Process Choices
A top answer never just says "steel is strong". It explains why that property suits the product, and weighs the drawbacks. Learn to justify a material or process choice, context by context.
Justify the choices, the way you are assessed
Free interactive practice on the decisions the assessment actually asks you to justify.
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More than a list
A weak answer says "aluminium is strong and light". A top answer says *why* those properties suit this product, and weighs the drawbacks. Topic 1.13 pulls together everything you know about materials to do one thing: justify a material, component or process choice for a product and how it is used.
The language of justifying
Four ideas run through this module:
Listing versus justifying
The same facts earn very different marks depending on whether you link them to the product.
From list to justification
What turns a list of properties into a justification?
- Explaining why the property suits how the product is used
- Naming as many properties as possible
- Simply making the answer longer
- Drawing a picture of the product
Match each property to its meaning
- Toughness
- Corrosion resistance
- Ductility
- Density
- Resists breaking when hit or dropped
- Does not rust or degrade in wet conditions
- Can be drawn into a wire without breaking
- How heavy a material is for its size
Match each product to the property it needs
- A saucepan base
- A garden bench
- A racing bike frame
- A crash helmet
- Good thermal conductivity
- Weather and corrosion resistance
- High strength with low weight
- Toughness to absorb an impact
The justifying recipe
To justify a choice, work through five moves: state the material or process, name the key property, link it to how the product is used, weigh a drawback, and conclude. That link, from property to purpose, is what earns the marks.
Build a justified answer
Put the steps of writing a justified choice into order.
- State the material or process you would choose
- Name the key property that matters
- Explain why that property suits how the product is used
- Weigh a drawback or trade-off
- Conclude with a justified recommendation
What makes it strong?
Select the TWO things that make a justification strong.
- Linking a property to how the product is used
- Weighing a drawback or trade-off
- Listing as many materials as possible
- Repeating the same property twice
Justifying in words
A good design answer does not just list a _____; it gives a _____ by linking the property to how the product is used. A designer often accepts a _____, such as a higher cost, to gain a better property. The choice must suit the _____ in which the product is used, and a strong answer ends with a clear _____.
Which ones justify a choice?
Tap the TWO statements that JUSTIFY a choice by linking a property to how the product is used.
- Stainless steel is chosen for the sink because it resists corrosion in constant water.
- uPVC suits window frames because it is weatherproof and needs little maintenance.
- Wood is a natural material.
- This metal is shiny and hard and heavy.
- Plastic is a kind of plastic.
The right property
A drinks can must be light and must not corrode. Alongside low weight, which property matters most?
- Corrosion resistance
- High density
- Brittleness
- Poor conductivity
Choose for the context
Match a material or idea to each design situation.
- A children's outdoor slide must be tough, weatherproof and colourful. Which material best suits it?
- A frying pan base needs to spread heat quickly and evenly. Which property matters most?
- A designer picks a cheaper material that is less durable, to keep the price down. What is this an example of?
Justify your choice
A company is designing a garden bench that must last for years outdoors. Recommend a suitable material, justify your choice by linking its properties to how the bench is used, and weigh one trade-off.
- Recommend a suitable material for an outdoor bench
- Name two properties that make it suitable
- Explain how each property suits being left outdoors
- Weigh one trade-off, such as cost or sustainability