Concentration — Science definition

Defined in 3 courses:

Where it is taught

In use

Concentration is how crowded the particles are — how much of a substance there is in a given volume.

Membrane Transport, Diffusion & Osmosis

Concentration is the general word for how much solute is packed into a given amount of solution.

Concentration & Molarity

Questions using concentration

Problem 1

Why can particle count alone fail to show concentration?
Answer and explanation

Concentration depends on both amount and volume; counts in unequal volumes are not directly comparable.

Problem 2

A model compartment has 12 solute units in 3 volume units. Find concentration.
Answer and explanation

4 solute units/volume unit

12/3=4 in the stated model units.

Problem 3

Dilution conserves solute amount only under the stated no-reaction conditionsDilution conserves solute amount only under the stated no-reaction conditionsBefore dilutionAfter dilutionc₁V₁ = nsolute = c₂V₂Same solute amount; larger solution volume lowers concentration.
Original equal-count dilution model; dot spacing and solvent volume are schematic rather than a molecular-scale simulation.
Interpret the supplied visual. Why does doubling final volume halve concentration in this selected dilution?
Answer and explanation

The unchanged solute amount is distributed through twice the solution volume, so n/V halves.

Dilution adds solvent while retaining the same amount of the specified solute, assuming no reaction, precipitation or loss. From n=cV, this gives c₁V₁=c₂V₂. The final volume V₂ is the total diluted solution volume, not merely the added solvent volume. The same expression should not be used automatically for reacting acid and base solutions, because the named solute amount can change. Draw a before-and-after entity inventory to identify what is actually conserved.

The unchanged solute amount is distributed through twice the solution volume, so n/V halves.

Response criteria

  • Interpret labels, structures, axes, units and directions correctly.
  • Explain the chemistry relationship or mechanism.
  • Respect stated assumptions and distinguish observation from inference.

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