K.B Chemistry 2024-2025 Mixtures and Pure Substances PDF

K.B Chemistry 2024-2025 Ms. K. Bhagaloo Chemistry form 3 Pure Substances and Mixtures Pure substances A pure substance is composed of a single type of material only. Any pure substance possesses certain general characteristics: Its composition is fixed and constant. Its properties are fixed an...

K.B Chemistry 2024-2025 Ms. K. Bhagaloo Chemistry form 3 Pure Substances and Mixtures Pure substances A pure substance is composed of a single type of material only. Any pure substance possesses certain general characteristics: Its composition is fixed and constant. Its properties are fixed and constant, for example, its melting point, boiling point and density. The component parts cannot be separated by any physical process. To find out if a substance is pure, its melting point or boiling point can be measured. If any impurities are present, they will usually lower its melting point and raise its boiling point. Eg: Elements and compounds are examples of pure substances. If a substance is pure, we cannot separate it into any other parts (components) by physical means. Pure water has only one component in it – water molecules. Pure sulphur has only one component in it – sulphur molecules. The composition of a compound is fixed Elements: An element is a pure substance that cannot be broken down into simpler substances by using any ordinary physical or chemical process. Compounds: A compound is a pure substance that is formed from two or more different types of elements which are chemically bonded together in fixed proportions and in a way that their properties have changed 1 K.B Chemistry 2024-2025 Mixtures A mixture consists of two or more substances (elements and/or compounds) which are physically combined together in variable proportions. Each component retains its own individual properties and is not chemically bonded to any other component of the mixture. Any mixture possesses certain general characteristics: Its composition can vary. Its properties are variable because its component parts keep their individual properties. Its component parts can be separated by physical means Homogeneous mixtures A homogeneous mixture is a uniform mixture; it has the same composition and properties throughout the mixture. It is not possible to distinguish the component parts from each other. All solutions are homogeneous mixtures. Heterogeneous mixtures A heterogeneous mixture is a non-uniform mixture; it is possible to distinguish the component parts from each other, though not always with the naked eye. Heterogeneous mixtures include suspensions and colloids. 2 K.B Chemistry 2024-2025 Example: 3