Colloids and Suspensions
Larger particles stay suspended without dissolving.
About this topic
Solutions, colloids and suspensions differ by particle size. Solutions have particles under 1 nm, are transparent and do not settle or scatter light. Colloids have particles from about 1 to 1000 nm, appear cloudy, do not settle, and scatter light (Tyndall effect), as in milk, fog and gelatin. Suspensions have larger particles that settle and can be filtered, like muddy water.
A colloid has a dispersed phase spread through a dispersion medium. Examples include foam (gas in liquid), emulsion (liquid in liquid, such as mayonnaise), aerosol (liquid in gas, such as fog), sol (solid in liquid, such as paint) and gel (liquid in solid, such as jelly). Colloid particles stay suspended because of constant collisions with solvent molecules (Brownian motion) and electrical charges that repel each other. Adding salt or heating can make them clump together, as when milk curdles.
You can see the Tyndall effect when sunlight beams through mist or when a laser pointer lights up a glass of dilute milk, but not through salt water. Emulsifiers like lecithin in egg yolk keep oil and water from separating in mayonnaise. Blood is a colloid, as are smoke and butter.
A misconception is that colloids are solutions; they differ because the particles are larger and scatter light. Another is that they separate on standing, which is true only for suspensions.
Key ideas
- Tyndall effect scatters light
- Milk is a colloid
- Suspensions settle
Quick check
Use cases: where Colloids and Suspensions helps
- Homework: review the key idea behind Colloids and Suspensions before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Colloids and Suspensions without notes.
- Visual learning: play with the interactive lab to see how Colloids and Suspensions changes when you adjust its inputs.
- Teaching a friend: explain Colloids and Suspensions in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Colloids and Suspensions?
Larger particles stay suspended without dissolving.
What will I learn in Colloids and Suspensions?
Tyndall effect scatters light. Milk is a colloid. Suspensions settle.
Is Colloids and Suspensions part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Colloids and Suspensions lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Colloids and Suspensions?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.