Study Notes
Matter can be classified into pure substances and mixtures. Elements — substances made of atoms with the same number of protons, found on the Periodic Table.
Example: Carbon (C)
Compounds — pure substances made of two or more elements chemically combined, with properties different from the elements that form them.
Example: Water (H₂O)
Mixtures — combinations of different substances not chemically joined, which can be separated by physical means.
Example: Air, which contains nitrogen, oxygen, and carbon dioxide
Solution — a homogeneous mixture of two or more substances, consisting of a solute dissolved in a solvent.
Example: Saltwater
Saturated Solution — a solution where no more solute can dissolve at a certain temperature.
Example: Sugar in tea at room temperature
Unsaturated Solution — a solution where more solute can still dissolve at a certain temperature.
Example: Sugar in hot tea
Concentration — the amount of solute dissolved in a solvent.
Example: Vinegar is a dilute solution of ethanoic acid in water
Exam Tips
Key Definitions to Remember
- An element is a substance made of atoms with the same number of protons.
- A compound is a pure substance made of two or more elements chemically combined.
- A mixture contains different substances not chemically joined.
- A solution is a homogeneous mixture of a solute and a solvent.
Common Confusions
- Confusing compounds with mixtures; compounds are chemically combined, mixtures are not.
- Thinking all solutions are liquids; solutions can be gases or solids too.
Typical Exam Questions
- What is an element? A substance made of atoms with the same number of protons.
- How can you separate a mixture of iron filings and sulfur? Use a magnet to attract the iron filings.
- What is the difference between a saturated and unsaturated solution? A saturated solution cannot dissolve more solute at a certain temperature, while an unsaturated solution can.
What Examiners Usually Test
- Understanding the difference between elements, compounds, and mixtures.
- Ability to classify substances as pure or mixtures.
- Knowledge of how to separate mixtures using physical methods.