The chemical earth dot point 1:
Homogeneous mixture: Uniform composition throughout, A substance or material that contains only one kind of compound or one element can be defined as homogeneous. E.g. sugar, petrol. Heterogeneous mixture: having a non – uniform composition
Element: a pure substance, which cannot be decomposed into simpler substances Compound: a pure substance, which can be decomposed into simpler substances, for example into elements. E.g. table salt (sodium chloride), alcohol (ethanol) and sugar (sucrose). Separation of solids of different sizes: separated by sieving Separating solids and liquids: separated by filtration, the liquid or solution that passes through the filter paper is called the filtrate. Sedimentation is the process in which solids settle to the bottom of a container. Decantation is the process of carefully pouring off the liquid and leaving the solid undisturbed at the bottom of the container. Distillation: the process in which a solution or mixture of liquids is boiled with the vapour formed being condensed back into a liquid in a different part of the apparatus and so separated from the mixture.
Separation method| Property used in the separation|
Sieving | Particle size|
Evaporation| Liquid has a much lower boiling point than the solid| Distillation| Big difference in boiling points|
Fractional distillation| Significant but small difference in boiling point| Adding a solvent, then filtration| One substance is soluble in the chosen solvent, while the others are insoluble| Filtration| One substance is a solid, the other a liquid or solution| Using a separation funnel| Components are immiscible liquids|
Properties used to identify pure substances:
* Physical state at room temperature
* Melting and boiling points
= Determining the quantities (masses) of substances present in a sample
Combined and uncombined...