At GCSE, the particle model of matter is built on three ideas: all substances are made of tiny particles; there are spaces between those particles; and the particles are in constant motion with energy that changes with temperature. The statement that lists these three ideas is the best because it directly reflects this model: every substance is composed of small particles, there are gaps between them that explain why things compress or expand, and the particles are always moving with energy that increases when you heat them and decreases when you cool them. This helps explain why different states behave differently and how heating changes things. For example, heating adds energy to the particles, making them move faster and spread out more, which can cause a solid to melt or a liquid to vaporize. On the other hand, if a statement claims particles are fixed in place at all temperatures, or that matter is continuous without particles, or that only liquids have particles, it conflicts with the observable facts that solids and gases also consist of particles and that particles are always moving to some degree.

The main practical skills being assessed are planning experiments, performing them safely and accurately, analysing the data collected, and evaluating the investigations. Planning involves deciding what to change, choosing suitable variables and controls, selecting appropriate measurements, and considering safety. Performing means carrying out the plan with careful technique, using equipment correctly, obtaining precise measurements, and following risk assessments. Analysing data is about turning measurements into meaningful information—calculating averages or rates, spotting trends, and checking for consistency. Evaluating experiments looks at sources of error, reliability and validity of results, and how the method could be improved. Practising all these together helps students design and carry out investigations, produce trustworthy evidence, and justify their conclusions, which is essential for GCSE success and real-world laboratory work.

Plates sliding horizontally past each other with no crust being created or destroyed describes a transform boundary. This boundary type is also called a conservative boundary, because the total amount of crust stays the same as the plates slip past one another. The motion is due to shear forces along faults, and earthquakes are common where rocks stick and then suddenly slip. An example is the San Andreas Fault in California. This differs from divergent boundaries, where new crust is formed as plates move apart, and convergent boundaries, where crust is destroyed as one plate dives beneath another.

Distillation uses differences in boiling points to purify a liquid. By heating the liquid, it forms vapor, which is then cooled in a condenser to return to a liquid that is collected separately. The vapor carries the component with the lower boiling point, leaving higher-boiling impurities behind in the original mixture, giving a purer distillate. This differs from filtration, which only removes solids, or evaporation, which removes solvent but doesn’t recapture a purified liquid by cooling. Chromatography separates components based on how they interact with a stationary phase and a mobile phase, not by heating and cooling the entire liquid. So the described method is distillation.