This definitions covers Key Definitions within Density for GCSE Physics. Revise Density in Particle Model for GCSE Physics with 13 exam-style questions and 30 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 7 of 13 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
📖 Key Definitions
Density (ρ): The mass per unit volume of a substance. ρ = m/V. Units: kg/m³ or g/cm³.
Mass (m): The amount of matter in an object. Measured in kilograms (kg). Does not change with location.
Volume (V): The amount of space an object occupies. Measured in m³ or cm³.
Displacement method: A technique for measuring the volume of an irregular solid by submerging it in water and measuring the volume of water displaced.
Upthrust: The upward force exerted by a fluid on a submerged object, equal to the weight of fluid displaced. If upthrust equals weight, the object floats.
Quick Check: A rock has a mass of 270 g and a volume of 100 cm³. What is its density in g/cm³?
Density = mass ÷ volume = 270 ÷ 100 = 2.7 g/cm³. This matches aluminium — the rock is likely granite or similar.
Practice questions for Density
What is the correct equation for density?
Explain why gases have a much lower density than solids, using ideas about particles.