The Concentration simulation from PhET lets you mix chemicals with water, watch the colour of the solution change, and read the molarity on a concentration meter. You can switch between solutes, add or remove water and solute, and find out how concentrated a solution can get before it becomes saturated. It is free, runs in any browser on a phone, tablet or laptop, and it is a great fit for solutions and dilution lessons in Tamil Nadu State Board (Samacheer Kalvi) Science and Chemistry.
What is the Concentration simulation?
This interactive simulation lets you make a solution by mixing a chemical with water. As you change the amounts, the colour of the solution gets stronger or lighter, and a concentration meter shows the molarity. You can switch to a different solute and see how far you can go before the solution is saturated. Because it runs on HTML5, there is nothing to install, and it works on phones, tablets, Chromebooks and computers.
Elementary school to university
Concentration, dilution and saturation
Phone, tablet, Chromebook, PC
English
PhET’s learning goals include relating volume and amount of solute to concentration, explaining how colour and concentration are related, predicting how concentration changes when water, solute or solution is added or removed, designing a procedure to make or change a concentration, and identifying a saturated solution.
Launch the Concentration simulation online
Tap or click inside the player and start mixing. Use the full-screen button in the player for a bigger view.
Credit: University of Colorado Boulder
How to use the Concentration simulation, step by step
- Predict first. Before you add anything, say what you think will happen to the colour and to the concentration.
- Add solute. Add more of the chemical to the water and watch the colour get stronger and the meter reading rise.
- Add water. Keep the amount of solute the same and add water. The colour gets lighter and the concentration falls. This is a dilution.
- Remove water. Take water out and see the concentration go up, because the same solute is now in less solution.
- Switch the solute and find saturation. Keep adding solute until the solution cannot take any more, and compare how different solutes behave.
Tip for students: change only one thing at a time, and always compare the colour with the number on the concentration meter.
The idea behind the simulation: M = n ÷ V and C₁V₁ = C₂V₂
M = n ÷ V | C₁V₁ = C₂V₂
Here M is the concentration (molarity) in mol/L, n is the amount of solute in moles and V is the volume of the solution in litres. When you dilute a solution, you add solvent but the amount of solute does not change, so C₁ × V₁ = C₂ × V₂.
Worked example: A solution has 0.3 mol of solute in 0.6 L, so M = 0.3 ÷ 0.6 = 0.5 mol/L. Now take 200 mL of a 1.5 M solution and dilute it to 600 mL. The new concentration is (1.5 × 200) ÷ 600 = 0.5 M, and you added 400 mL of water. Try the same changes in the simulation and watch the colour fade.
Solution key terms explained
These are the words you will meet while using the Concentration simulation, with simple meanings.
Solute
The substance that dissolves, such as a salt or a dye.
Solvent
The substance that does the dissolving. In this simulation it is water.
Solution
The uniform mixture formed when a solute dissolves in a solvent.
Concentration
How much solute is present in a given volume of solution.
Molarity (M)
Concentration in moles of solute per litre of solution (mol/L).
Mole (mol)
A unit for the amount of a substance. One mole contains about 6.022 × 1023 particles.
Dilution
Adding solvent to lower the concentration. The amount of solute does not change.
Saturated solution
A solution that cannot dissolve any more solute at that temperature.
Solubility
The most solute that can dissolve in a solvent. It differs from one solute to another.
Common mistakes: Thinking that adding more solute to a saturated solution makes it more concentrated (the extra solute just stays undissolved), forgetting that removing water raises the concentration, and mixing up the amount of solute with its concentration.
Try the dilution calculator (practice what you explore)
Enter the starting concentration, the starting volume and the final volume to see the new concentration and how much water to add or remove. Then tap a “what if” button.
What happens to concentration when you change a variable
| Change | Effect on concentration |
|---|---|
| Add solute (same volume) | Concentration increases |
| Add water (same solute) | Concentration decreases |
| Remove water (same solute) | Concentration increases |
| Volume doubled (same solute) | Concentration halves |
| Add solute to a saturated solution | Concentration stays the same |
Classroom activities for teachers
The Concentration simulation fits a single 40-minute period.
- Predict and test (10 min): students write a prediction before each change, then check it on the concentration meter.
- Design a procedure (10 min): pairs plan how to make a solution of a target concentration, then test the plan.
- Dilution challenge (10 min): students change a solution from one concentration to another and justify each step with C₁V₁ = C₂V₂.
- Exit ticket (10 min): students explain in two sentences why adding water lowers the concentration.
Looking for the matching chapters? Browse the Science and Chemistry books on TN SchoolBooks and download the Samacheer Kalvi PDFs, then use this simulation to make the solutions lessons visual. More free science simulations and textbook PDFs are on the home page.
Quick quiz: test your understanding of concentration
Score: 0 / 5
Concentration simulation: frequently asked questions
Is the Concentration simulation free?
Yes. PhET simulations are free to run online in a browser. Check PhET’s licensing page for reuse terms.
Does it work on a mobile phone?
Yes. It is built with HTML5 and works on phones, tablets and Chromebooks. Use landscape mode or the player’s full-screen button for a bigger view.
What is the concentration of a solution?
Concentration tells you how much solute is dissolved in a given volume of solution. A common unit is molarity, which is moles of solute per litre of solution (mol/L).
What is a saturated solution?
A saturated solution has dissolved as much solute as it can at that temperature. If you add more solute, it does not dissolve, so the concentration does not rise.
The Concentration simulation turns an abstract idea into something you can mix, measure and see. Explore it, take the quiz above, and keep experimenting until predicting the concentration feels easy.