Density Edexcel International GCSE Physics revision
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In plain words
Density is how tightly matter is packed: how many grams there are in each cubic centimetre. A brick and a sponge the same size don't weigh the same, because the brick is denser. Things less dense than water float on it; denser things sink.
Three things to know
- Density = mass ÷ volume (ρ = m/V). Common units are g/cm³ and kg/m³.
- Find the volume of an irregular solid from the rise in water level when it is lowered into a measuring cylinder.
- An object floats in a liquid if its density is less than the liquid's.
Worked example
A metal block of mass 240 g has a volume of 30 cm³. Find its density.
- Density = mass ÷ volume.
- = 240 ÷ 30 = 8 g/cm³.
Tips and tricks
- For an awkwardly shaped object, find the volume from how far the water level rises in a measuring cylinder.
- Check the units match: g with cm³, or kg with m³. 1 g/cm³ is 1000 kg/m³.
It lands in your notebook with its questions as flashcards.
Density: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
A cube has sides of 2 cm and a mass of 40 g. What is its density?
Volume = 2 × 2 × 2 = 8 cm³, and 40 ÷ 8 = 5 g/cm³.
Which measurements are needed to find the density of a liquid?
Density is mass divided by volume.
A solid has density 0.8 g/cm³. Water has density 1.0 g/cm³. What happens when the solid is put in water?
It is less dense than water, so it floats.
The density of aluminium is 2.7 g/cm³. What is the volume of 81 g of aluminium?
Volume = mass ÷ density = 81 ÷ 2.7 = 30 cm³.
What is 1 g/cm³ in kg/m³?
There are a million cm³ in a m³ and a thousand grams in a kilogram: 1 000 000 ÷ 1000.
Why does oil float on water?
A less dense liquid floats on a denser one that it doesn't mix with.
Quiz
6 questions
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Worksheet
4 questions, 9 marks. Write your answers on paper, then check them.
Density
Edexcel International GCSE Physics 4PH1 · 9 marks · papermunch.org
Name ______________________________ Date ______________
A block has a mass of 540 g and a volume of 200 cm³. Calculate its density.[2]
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2.7 g/cm³. Density = 540 ÷ 200.
A stone of mass 96 g raises the water level in a measuring cylinder from 50 cm³ to 82 cm³. Calculate the density of the stone.[3]
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3.0 g/cm³. Volume = 82 − 50 = 32 cm³; density = 96 ÷ 32.
The density of cooking oil is 0.92 g/cm³. Calculate the mass of 250 cm³ of oil.[2]
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230 g. Mass = density × volume = 0.92 × 250.
Ice has a density of 0.92 g/cm³ and water 1.0 g/cm³. Explain why ice floats on water.[2]
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Ice is less dense than water.
Answers: Density
- 1. 2.7 g/cm³. Density = 540 ÷ 200.
- 2. 3.0 g/cm³. Volume = 82 − 50 = 32 cm³; density = 96 ÷ 32.
- 3. 230 g. Mass = density × volume = 0.92 × 250.
- 4. Ice is less dense than water.