KS3

How to work out density

Part of MathsCompound measures

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A short video showing how to work out density.

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Click to see a step-by-step slideshow.
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WHAT YOU NEED: a ruler, whiteboard, calculator, red pen and green pen.
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STEP 1: Find the volume and mass of the object. Here it is 2 cm³ and 38 g.
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STEP 2: Write out the problem, circle the key pieces of information and draw a bar. Label the whole bar 38 g. Draw a second bar directly underneath the first and label the end 2 cm³.
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STEP 3: Write out the equation to work out density. Use the ruler to draw a vertical line in the middle of the bottom bar. Shade the area to the left, label this 1 cm³. Repeat on the top bar, labelling the shaded area with a question mark.
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STEP 4: Write out the equation. Here it is the mass, 38 g, divided by the volume, 2 cm³. Before you use a calculator, can you estimate in your head what the answer might be?
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Use a calculator to check your answer. You've done it! The answer is 19 g / cm³. This is the equivalent of the shaded area of the top bar. Did you know the density of pure gold is 19 g / cm³? Lead is only 11 g / cm³.

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