Combined Science57 views·Updated 26 Jun 2026·4 pages

Density Practice Questions and Detailed Answers

Los@los

Add to Google sources

Density is one of the most useful concepts in physics...

1 / 4

of 4

Density

Examples

1 A student pours out 1 litre of a liquid and finds its mass is 0.7 kg. Calculate the
density of the liquid.

Step 1: Wri

Basic Density Calculations

Density is simply how much mass is packed into a given volume - think of it as how "heavy" something feels for its size. The formula is straightforward: density = mass ÷ volume.

When tackling density problems, always start by writing down what you know and what you're looking for. Then convert your units carefully - you'll usually work with either grams and cm³ or kilograms and m³, but stick to one system throughout.

The key trick is remembering your conversions: 1 litre = 1000 ml = 1000 cm³, and 1 kg = 1000 g. Get these right, and the rest becomes much easier.

Quick Tip: Always check your units match before plugging numbers into the formula - mixed units are the biggest source of errors in density calculations!

of 4

Finding Mass from Density

Sometimes you'll need to find mass instead of density, which means rearranging the formula. Don't panic - it's just basic algebra! If density = mass ÷ volume, then mass = density × volume.

The process stays the same: write down what you know, calculate any missing values (like volume from dimensions), then substitute into your rearranged formula. Remember that volume of a rectangular block is length × width × height.

Always double-check your final answer makes sense. A small wooden block shouldn't weigh 20 kg, and a tennis ball shouldn't have the same density as lead!

Study Smart: Practice rearranging the density formula until it becomes automatic - you'll use this skill in chemistry and other physics topics too.

of 4

Real-World Applications

Density is brilliant for identifying materials - that's how the miner can tell real gold $19 g/cm³$ from fool's gold $5 g/cm³$ . Even if the sample isn't perfectly pure, densities that are much closer to the real thing usually indicate authenticity.

Different states of matter have different densities too. Molten iron $7.0 g/cm³$ is less dense than solid iron $8.0 g/cm³$ , which explains why it expands when heated and contracts when cooling.

Water displacement is a clever way to measure volume of irregular objects. When something displaces 300 cm³ of water, that's exactly the volume of the object - no complicated measuring required!

Real Life: This is exactly how archaeologists test whether ancient artifacts are made from the materials they claim to be!

of 4

Floating and Sinking

Objects float when their density is less than the liquid they're in - that's why ice $about 0.9 g/cm³$ floats on water $1.0 g/cm³$ . This principle helps you solve tricky problems about boats, fish tanks, and floating objects.

When calculating maximum loads, remember to add up all the masses involved. A 1 kg fish tank plus 15.54 kg of water equals 16.54 kg total - too heavy for a shelf that only holds 16 kg!

For objects that start floating but gradually fill with water, calculate how much extra mass they can take before their overall density reaches 1.0 g/cm³. Once they hit that magic number, down they go!

Physics Fact: This is why damaged ships eventually sink - as water fills the hull, the ship's average density increases until it exceeds that of seawater.

We thought you’d never ask...

What is the Knowunity AI companion?

Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.

Where can I download the Knowunity app?

You can download the app from Google Play Store and Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Most popular content in Biology

Biology

Cell Biology and Cell structure

cell structures

93,2520

Biology

AQA Biology: Key Concepts

Explore essential AQA Biology topics including Photosynthesis, Respiration, Homeostasis, Genetics, and Ecology. This comprehensive knowledge organizer covers key concepts such as energy transfer, hormonal control, and genetic variation, providing a solid foundation for your studies. Ideal for exam preparation and understanding biological processes.

108,794306

Biology

The functions of subcellular structures - B1 Biology

Flashcards on the different functions of subcellular structures: cell membrane, nucleus, mitochondria, ribosomes, cytoplasm, permant vacuole, chloroplasts and cell wall.

102,8105

Biology

Biology paper 1 Summary

Notes for Biology paper 1 contains the full course for AQA higher combined!

104,132106

Physics

Forces and Motion Overview

Explore key concepts in Forces and Motion, including Hooke's Law, velocity, acceleration, and the principles of moments. This summary covers essential topics such as the relationship between force and extension, terminal velocity, and the impact of safety devices in physics. Ideal for AQA Physics Unit 5 revision.

109,191872

Combined Science

Comparing Eukaryotic and Prokaryotic Structures

Compare animal and plant cells with bacterial cells, focusing on size differences, organelle presence, and genetic material storage.

S39370

Combined Science

Atomic Mass and Number Calculations

Calculate the number of protons, neutrons, and electrons for different elements using atomic and mass numbers.

S39810

Chemistry

Essential Chemistry Practicals

Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.

1011,972902

Biology

GCSE Biology Practicals Overview

Explore essential GCSE Biology practicals covering key concepts such as photosynthesis, enzyme activity, microbial growth, and experimental design. This comprehensive guide includes step-by-step procedures, potential errors, and calculations for each practical, ensuring a solid understanding of biological processes and laboratory techniques.

1016,7591,391

Most popular content

Sociology

Sociology of Education Overview

Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.

12102,8893,041

Sociology

Sociology of Families: Comprehensive Revision

Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.

1273,6832,307

Criminology

Criminology: Crime & Punishment Overview

Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.

1254,8741,059

Sociology

Comprehensive Crime & Deviance Overview

Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.

1251,6591,399

Biology

Cell Biology and Cell structure

cell structures

93,2520

English Literature

An Inspector Calls: Character Insights

Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.

1025,434907

Criminology

WJEC Unit 4 Criminology

Criminology unit 4 detailed revision note

127,155125

Criminology

Criminology Theories Overview

Explore key criminology theories and their implications on crime and deviance. This comprehensive summary covers biological, psychological, and sociological perspectives, including labelling theory, right realism, and the impact of social campaigns on policy development. Ideal for A-Level criminology students seeking to understand the complexities of criminal behaviour and the factors influencing crime prevention strategies.

129,762210

English Literature

Romeo and Juliet: Key themes

Key Romeo and Juliet themes and analysed quotes

106,712198

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.6/5App Store

4.7/5Google Play

The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.

Stefan SiOS user

This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.

Samantha KlichAndroid user

Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.

AnnaiOS user

Combined Science57 views·Updated 26 Jun 2026·4 pages

Density Practice Questions and Detailed Answers

Los@los

Add to Google sources

Density is one of the most useful concepts in physics - it helps explain why ice floats, how ships stay afloat, and even how miners identify real gold! Understanding density calculations will give you the tools to solve loads of...

of 4

Basic Density Calculations

Density is simply how much mass is packed into a given volume - think of it as how "heavy" something feels for its size. The formula is straightforward: density = mass ÷ volume.

The key trick is remembering your conversions: 1 litre = 1000 ml = 1000 cm³, and 1 kg = 1000 g. Get these right, and the rest becomes much easier.

Quick Tip: Always check your units match before plugging numbers into the formula - mixed units are the biggest source of errors in density calculations!

of 4

Finding Mass from Density

Sometimes you'll need to find mass instead of density, which means rearranging the formula. Don't panic - it's just basic algebra! If density = mass ÷ volume, then mass = density × volume.

Always double-check your final answer makes sense. A small wooden block shouldn't weigh 20 kg, and a tennis ball shouldn't have the same density as lead!

Study Smart: Practice rearranging the density formula until it becomes automatic - you'll use this skill in chemistry and other physics topics too.

of 4

Real-World Applications

Water displacement is a clever way to measure volume of irregular objects. When something displaces 300 cm³ of water, that's exactly the volume of the object - no complicated measuring required!

Real Life: This is exactly how archaeologists test whether ancient artifacts are made from the materials they claim to be!

of 4

Floating and Sinking

When calculating maximum loads, remember to add up all the masses involved. A 1 kg fish tank plus 15.54 kg of water equals 16.54 kg total - too heavy for a shelf that only holds 16 kg!

Physics Fact: This is why damaged ships eventually sink - as water fills the hull, the ship's average density increases until it exceeds that of seawater.