Section outline
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In this course you will learn about:
- Capacity.
- The difference between capacity and volume.
- The different units of capacity.
- How to convert between the different units of capacity.
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What is capacity?
The amount of substance that an object can hold is referred to as its capacity. Put in another way, an object's capacity is simply the total amount of space, interior to the object, which can be filled.
But is capacity the same as volume?
NO!
Volume refers to how much space an object takes up. It's the amount of 3-dimensional space covered by an object. In terms of this course, it's important to understand that liquids are also measured in volume.
The volume of a liquid is the amount of space it takes up in an object whereas the capacity is the total amount of liquid that the object can hold. Let's look at this by way of an example:
You purchased a 500 ml carton of milk. The capacity of the carton is 500 ml. The physical volume of the carton container will be equal to the height x width x depth. You then drink 300 ml of the milk. The following has occurred:
- The capacity stays the same at 500 ml.
- The physical volume of the carton stays the same since physically it hasn't changed.
- The volume of liquid inside the carton has decreased to 200 ml (500 ml - 300 ml).
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View the images below:
You'll notice that each of the above containers have a 1 litre capacity, but their sizes and shapes are different. We can therefore deduce that the containers have a different volume (they take up different amounts of space) but the same capacity of carrying 1 litre of liquid.
When the container is full and hasn't been opened, the capacity and volume of liquid will be equal. Once you start using the contents in the container, the capacity will stay the same at 1 litre, but the volume of liquid will decrease according to how much liquid you have used.
Watch the short YouTube video below which clarifies this difference.
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Now that you have consolidated what the prefixes mean, let's explore how one would convert between the different units of measure. Note that the relationship between the units of measurement are all based on powers of 10.
Remember the golden rule:
- If you want to convert from a smaller to larger unit, you need to multiply
- If you want to convert from a larger to smaller unit, you need to divide
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Summary
In this unit you learnt about the difference between capacity and volume:
Capacity means how much substance an object can hold. Volume means how much space an object or substance takes.
The base unit of measurement for capacity and liquid volume is the litre. It's important to remember that the same conversion rules apply when converting from one unit of measure to another. Converting from the smaller to larger units one must always divide or move the decimal point to the left. When converting from larger to smaller units one must multiply or move the decimal point to the right.
It's important to familiarise yourself with these rules and to understand what the prefixes mean since this will stand you in good stead when you are required to convert units of measure in everyday life, e.g. when cooking.
