Solute vs Solvent vs Solution: What's the Difference?
The difference between a solute and a solvent comes down to the job each one does: the solute is what dissolves, the solvent is what does the dissolving, and the solution is the homogeneous mixture that results. Stir salt into water and all three are in front of you at once. Salt is the solute, water is the solvent, and the saltwater is the solution. When you are working out solute vs solvent, the deciding question is usually which substance there is more of.
Key takeaways
- The solute is the substance that dissolves. The solvent is the substance it dissolves into, and it is present in the greater amount.
- The solution is the whole thing: a homogeneous mixture in which solute particles are spread evenly and never settle out.
- To identify the solvent, find the component whose physical state matches the state of the solution. If both start in the same state, the greater amount wins.
- Solutions do not have to be liquid. Air is a gaseous solution and brass is a solid solution.
- Dissolve 10 g of salt in 90 g of water and you get 100 g of solution that is 10% salt by mass.
Solute vs solvent vs solution: what does each one do?
Start with saltwater and the three roles stay straight for good. Drop 10 g of table salt into 90 g of water and stir. The salt disappears, but nothing has been lost. You are now holding 100 g of saltwater, and boiling the water away would give back every gram of salt.
The salt is the solute. It is the substance being dissolved, present in the smaller amount, and it breaks into particles far too small to see or filter.
The water is the solvent. It is the substance doing the dissolving, it is present in the greater amount, and it decides that the finished mixture is a liquid.
The saltwater is the solution. It is the solute and the solvent taken together as one uniform substance. Chemists label it NaCl(aq), where (aq) is short for aqueous and means dissolved in water.
A useful check: solute plus solvent always equals solution, in mass and in matter. Dissolving rearranges particles; it never creates or destroys them.
Solute vs solvent vs solution at a glance
The table below sets the three side by side. Read across a row to compare, and down a column for what each term means alone.
| Solute | Solvent | Solution | |
|---|---|---|---|
| What it is | The substance that dissolves | The substance that does the dissolving | The homogeneous mixture that results |
| Amount present | The smaller amount | The greater amount | Solute and solvent combined |
| Physical state | Solid, liquid, or gas | Solid, liquid, or gas | Matches the state of the solvent |
| In saltwater | Salt (NaCl) | Water (H₂O) | Saltwater, written NaCl(aq) |
| In air | Oxygen, argon, trace gases | Nitrogen | Air |
| Separated how? | By physical means such as evaporation or distillation, because nothing is chemically bonded | ||
How do you tell which substance is the solvent?
Two rules settle almost every case. The first is the state rule: the solvent is the component whose physical state matches the state of the finished solution. Dissolve a solid in a liquid and the mixture stays liquid, so the liquid is the solvent. Dissolve a gas in a liquid, as in sparkling water, and the mixture is still liquid, so water is the solvent.
The second rule covers the case where both components start in the same state, which is what usually happens with two liquids. Then whichever is present in the greater amount is the solvent. Mix 95 mL of ethanol with 5 mL of water and ethanol is the solvent. Reverse the amounts and water is.
That second rule produces an answer students often find surprising. Concentrated sulfuric acid is roughly 98% H₂SO₄ and 2% water by mass, so the acid is the solvent and the water is the solute. One caveat: chemists often call water the solvent by convention whenever it is present, so check how a particular source is using the word.
Can a solution be a solid or a gas?
Yes. Nothing in the definition of a solution requires a liquid. A solution is any homogeneous mixture whose components are spread evenly at the level of individual atoms, ions, or molecules, and that can happen in all three states of matter.
Gas in gas. Air is a solution. Dry air is about 78% nitrogen, 21% oxygen, and 1% argon, with traces of other gases, so nitrogen is the solvent and everything else is a solute.
Gas in liquid. Sparkling water is carbon dioxide dissolved in water. The water is the solvent, the gas is the solute, and the solution is liquid.
Solid in solid. Brass is zinc dissolved in copper, with common grades running around two-thirds copper. Sterling silver is 92.5% silver with 7.5% copper. In each, the metal present in greater amount is the solvent, and atoms of the other sit inside the same crystal structure.
One caveat: not every alloy is a true solid solution. Some contain separate crystalline regions of different composition, making them heterogeneous mixtures instead.
How do you describe how much solute a solution holds?
Two pairs of words do most of the work. Dilute and concentrated are relative terms. A dilute solution has little solute for the amount of solvent present, and a concentrated one has a lot. They compare, but they do not measure.
Unsaturated and saturated are precise. A saturated solution holds the maximum solute that will dissolve at that temperature, with any extra sitting undissolved at the bottom in equilibrium with the dissolved particles. Water at 25 °C dissolves about 36 g of salt per 100 g of water. Add 40 g and roughly 4 g stays on the bottom. Anything below that limit is unsaturated. A supersaturated solution holds more than the limit and is unstable, which is what makes rock candy and reusable hand warmers work.
For real numbers you need concentration. The simplest measure is percent by mass: divide the mass of solute by the mass of the whole solution, then multiply by 100. The 10 g of salt in 100 g of saltwater above works out to 10% by mass. Seawater, for comparison, averages about 3.5% dissolved salts.
Why is a solution a mixture and not a compound?
Because nothing in a solution is chemically bonded to anything else in it. Salt is a compound and water is a compound, but saltwater is neither. A compound has a fixed formula and a fixed ratio: water is always two hydrogens to one oxygen, and only a chemical reaction can take it apart. A solution has no fixed ratio. You choose how much salt to add.
That difference shows up in how you separate them. Boil saltwater and the water leaves as vapor while the salt stays behind, both chemically unchanged. Evaporation, distillation, and crystallization are enough, because no bonds have to break.
What separates solutions from other mixtures is that they are homogeneous. The dissolved particles are individual ions or molecules smaller than about a nanometer, too small to scatter light, settle, or be caught by filter paper. That is why a true solution looks clear even when it is deeply colored. Milk and fog are colloids, whose larger particles do scatter light, and muddy water is a suspension that settles.
Frequently asked questions
What is the difference between a solute and a solvent?
The solute is the substance that gets dissolved, and the solvent is the substance that dissolves it. The solvent is present in the greater amount and normally sets whether the solution is a solid, a liquid, or a gas. In sugar water, sugar is the solute and water is the solvent.
Is salt the solute or the solvent in saltwater?
Salt is the solute. It is present in the smaller amount and it is the substance that disappears into the water, splitting into sodium and chloride ions. Water is the solvent, because there is far more of it and it keeps the finished mixture liquid.
Can a solution have more than one solute?
Yes, and most real solutions do. Seawater contains sodium chloride plus magnesium, sulfate, calcium, and potassium salts, all dissolved in the same water. Air holds oxygen, argon, and several trace gases dissolved in nitrogen. A solution has only one solvent, but the number of solutes is not limited.
Is every mixture a solution?
No. Every solution is a mixture, but a mixture only counts as a solution if it is homogeneous down to individual particles. Muddy water and oil-and-vinegar dressing are mixtures that separate on standing, so they are suspensions rather than solutions.
Need a precise definition of solute, solvent, solution, or any term around them? Search the word in the A to Z Chemistry Dictionary.