GCSE Chemistry (Triple) Eduqas
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42 topics in 12 modules
☑️ Pure Substances and Mixtures 4 topics
- Purity of a Substance
- Elements, Compounds and Mixtures
- Chemical Processes
- Chromatography
☑️ Particles and Atomic Structure 2 topics
- The Particle Model
- Atomic Structure
☑️ Chemical Formulae, Equations and Amount of Substance 4 topics
- Chemical Formulae
- Balanced Chemical and Half Equations
- Balanced Ionic Equations
- Amount of Substance
☑️ The Periodic Table and Properties of Elements 4 topics
- The Periodic table
- Group 1 Elements
- Group 7 Elements
- Group 0 Elements
☑️ Bonding, Structure and Properties 4 topics
- Ionic Bonding
- Covalent Bonding
- Metallic Bonding
- Nanoparticles
☑️ Reactivity Series and Extraction of Metals 4 topics
- The Reactivity Series
- Oxidation
- Electrolysis
- Metal Extraction
☑️ Chemistry of Acids 5 topics
- pH
- Titrations
- Preparation of Salts
- Weak and Strong Acids
- Moles
☑️ Energy Changes in Chemistry 2 topics
- Endothermic and Exothermic Reactions
- Energy Changes
☑️ Rate of Chemical Change and Dynamic Equilibrium 3 topics
- Rates of Reaction
- Catalysts
- Dynamic Equilibrium
☑️ Carbon Compounds 2 topics
- Crude Oil
- Polymers
☑️ Production, Use and Disposal of Important Chemicals and Materials 5 topics
- The Haber Process
- Use and Disposal of Important Chemicals
- Use and Disposal of Important Materials
- Life Cycle Assessment of a Material/Product
- Recycling
☑️ The Earth and its Atmosphere 3 topics
- Forming of the Atmosphere
- Global Warming - The Greenhouse Effect
- Man-Made Causes of Climate Change
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GCSE Chemistry (Triple) Eduqas Revision Content
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GCSE Chemistry (Triple) Eduqas - Pure Substances and Mixtures - Purity of a Substance Content Preview
Pure Substances and Mixtures
Purity of a Substance
Purity of a Substance
Definition
- Purity refers to a substance that consists of only one type of particle.
- A substance can be said to be pure if it has a fixed boiling and melting point, which corresponds to the standard value.
Impurities and Effect on Boiling Point
- Impurities in a substance lead to changes in the boiling and melting points.
- An impurity in a substance causes an increase in the boiling point and a decrease in the melting point of that substance.
- The presence of impurities in a substance can lead to a range of boiling and melting points, rather than a fixed point.
Impurities and Effect on Melting Point
- The melting point of an impure substance is lower than that of a pure one.
- The range over which the substance melts is also typically broader for impure substances compared to pure substances.
Testing for Purity
- Melting point and boiling point tests are the common methods for testing the purity of a substance.
- Chromatography is another technique used to check the purity of a substance. This technique separates out each component in a mixture and allows identification of each.
Using Chromatography to Determine Purity
- Chromatography builds on the premise that different substances move at different rates on a coated surface.
- The distance moved by each component is specific to its identity, size, and shape, enabling it to be identified.
- The retention factor (Rf) is a number that allows identification of a substance. It is calculated by dividing the distance moved by the substance by the total distance moved by the solvent.
Remember, a pure substance will always have the same properties and compositions, irrespective of its source or method of preparation. However, use rigorous testing methods to achieve conclusive results.
Question: Explain how the presence of impurities in a substance affects its melting point and boiling point.
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