Purity, Formulations, and Chromatography
This page introduces fundamental concepts in chemical analysis, focusing on purity, formulations, and chromatography. It provides essential information for students studying GCSE chemical analysis.
The concept of purity in chemistry is explained as a single element or compound not mixed with any other substance. Students learn how to determine the purity of a substance by measuring its melting or boiling point and comparing it to the known values for the pure substance. The closer the measured point is to the reference value, the purer the substance.
Highlight: Impurities can lower the melting point of a substance and cause a broader melting point range.
The document then introduces formulations, which are useful mixtures created for specific purposes following a precise formula. These are made by carefully measuring and mixing components to achieve desired properties.
Example: Examples of formulations include fuels, cleaning agents, paints, medicines, alloys, fertilizers, and foods.
Chromatography, a crucial technique in GCSE chemistry, is presented as a method for separating mixtures and identifying substances. The process involves two phases:
- Mobile phase: The solvent in which particles can move.
- Stationary phase: The substance usuallypaper where particles remain fixed.
Vocabulary: Rf value - The ratio between the distance traveled by the dissolved substance and the distance traveled by the solvent.
The document explains how to calculate the Rf value and use it to differentiate between pure and impure substances. A pure substance produces a single spot on the chromatogram, while an impure substance results in multiple spots.
The page concludes with a step-by-step method for performing chromatography, which is essential knowledge for the AQA GCSE Chemistry chromatography Required practical.
