Mixture — Science definition

Substances combined in variable proportions without one new fixed composition.

Where it is taught

In use

A mixture contains substances together in variable proportions.

Classifying Matter & Separating Mixtures

Questions using mixture

Problem 1

A mixture contains 5 g salt and 8 g sand. After complete physical separation, what total dry solid mass should be recovered in a closed no-loss model?
Hints

List the given quantities, select a relationship, and check units before substituting.

Answer and explanation

13 g

5+8=13; material is redistributed, not created.

Problem 2

Classify pure copper, distilled water and air as element, compound or mixture. Show the reasoning, not just the conclusion.
Hints

Filtering alone cannot normally remove dissolved salt ions.

Answer and explanation

Copper is an element, water a compound, and air a mixture of gases under ordinary conditions.

Problem 3

Why does a variable composition support calling a material a mixture?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

Mixture proportions can vary without a single fixed chemical formula; a pure compound has defined composition.

Problem 4

A mixture contains 6.00 g salt and 4.00 g sand. You recover 5.10 g of dry salt-containing material. Calculate apparent salt recovery and explain why its purity remains uncertain.
Answer and explanation

Apparent recovery is 5.10/6.00 ×100 = 85.0%. The calculation treats the recovered mass as salt, but residual sand or other substances require a separate purity test. Distinguish mass loss from composition evidence.

Apparent recovery is 5.10/6.00 ×100 = 85.0%. The calculation treats the recovered mass as salt, but residual sand or other substances require a separate purity test. Distinguish mass loss from composition evidence.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the chemical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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