Numeracy Skills
in D&T
MEASURING WEIGHT & CAPACITY
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What is weight?
What is weight?
A weighing scale shows mass (in kilograms, kg), not weight (in Newtons, N). Weight is the force due to gravity acting on a mass. Even though it IS a force that causes a weighing scale to move down, we remove gravity from the reading on the scales, leaving just the mass reading. Weight force is calculated by multiplying the object mass (in kg) by the acceleration due to gravity g (in metres per second squared).
Because gravity is different on different planets, weight can change for an object because it is a force. Mass however, is fixed. An object on Earth has the same mass as the same object on the moon.
Measuring weight using metric & imperial scales
Measuring weight using metric & imperial scales
If we don't weigh our ingredients accurately, then there is a very high chance our food creations will fail, they might be too thick, too runny, too soft, too hard, too stodgy, might not mix, might not rise, etc.
Why do we use weighing scales in cooking? Because recipes are designed around 'ratios'. i.e. so much of 'this' mixes with so much of 'that'. To maintain the correct ratio, we need to weigh objects using scales.
Interpreting weighing scales - How to do it
Interpreting weighing scales - How to do it
Have a look a this poster. It contains some useful information about the interpretation of weighing scales and different units.
Comparing the magnitude (size) of different units
Comparing the magnitude (size) of different units
Sometimes it is really hard to visualise how large one unit is compared to another. This 'unit conversion tube map' might help you do this..
You can also use it to convert values directly.
Activity 1.6 - Metric weighing scales
Activity 1.6 - Metric weighing scales
Activity 1.7 - Imperial weighing scales
Activity 1.7 - Imperial weighing scales
What is capacity?
What is capacity?
Capacity is a way of describing the volume of something. Volume is how much 3d space something takes up. We usually use capacity to measure the amount of wet ingredients such as milk or water when cooking in the kitchen. Capacity is sometimes used for dry ingredients too, such as flour or oats.
A common imperial unit for capacity still in use is 'cups'. The 'conversion tube map' at the top of the page will help you learn about and convert between units.
Measuring capacity using metric & imperial scales
Measuring capacity using metric & imperial scales
This section will test your ability to read from jug measuring scales. You will be tested on your ability to read metric units, specifically litres, l and millilitres, ml although you should also be able to use imperial units too.
Do not confuse capacity (volume) with how heavy something is - however the link between the two properties is known as density. Density is the mass of something for a given volume. The more something is packed into a given space, the denser it is.
Density is measured in kg/m³.
Dish size and lining calculator
Dish size and lining calculator
This little tool will help you work out what size dish to use to fit a recipe for a jug capacity and the minimum amount of paper needed to line the dish. You can choose from what you've got available in your cupboard based on how deep the dish is.
When you've had a play with the tool, attempt the metric and imperial capacity assessments below.
Activity 1.8 - Metric jug capacity
Activity 1.8 - Metric jug capacity
Activity 1.9 - Imperial jug capacity
Activity 1.9 - Imperial jug capacity
'Weight & Capacity' Practice Worksheets
'Weight & Capacity' Practice Worksheets
Full walkthrough lessons with costing exercises.
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