Matter, Materials and Their Properties
Matter, Materials and Their Properties tests particle explanations of states, physical versus chemical changes, characteristic properties, mixtures, separation techniques, and conservation of mass. Questions often ask you to classify a change or choose a method to separate a mixture.
Core concepts
- All matter is made of particles in constant motion; spacing and motion explain solids, liquids, gases, diffusion, and changes of state.
- Physical changes alter form or state but not substance identity; chemical changes form new substances, often with evidence such as gas, precipitate, color change, or energy change.
- Characteristic properties such as density, melting point, boiling point, solubility, and conductivity help identify substances.
- Mixtures can be separated by physical methods: filtration, evaporation, distillation, magnetism, and chromatography.
- In a closed system, mass is conserved during chemical reactions.
Worked example
A 50 g irregular stone is lowered into 20 mL of water in a graduated cylinder; the water level rises to 40 mL. Volume = 40 minus 20 = 20 mL = 20 cm3. Density = mass divided by volume = 50 g divided by 20 cm3 = 2.5 g/cm3. The reasoning depends on the stone sinking and not dissolving; if it floats or absorbs water, displacement is not reliable.
Traps that cost marks
Confusing mass with weight; thinking dissolved sugar disappears; calling melting a chemical change; reading the meniscus incorrectly; using total volume instead of displaced volume; assuming every color change is chemical.