GCSE Chemistry (Combined) Eduqas
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33 topics in 1 module
☑️ Core 33 topics
- Purity of Substance
- Elements, Compounds and Mixtures
- Chromatography
- Purification Techniques
- The Particle Model
- The Atom
- Relative Atomic Mass
- Formulae of Elements and Covalent and Ionic Compounds
- Conservation of Mass
- Balanced Ionic Equations
- The Periodic Table
- Group 1 Elements
- Group 7 Elements
- Group 0 Elements
- Ionic Bonding and Structure
- Covalent Bonding and Structure
- Metallic Bonding and Structure
- Reactivity Series
- Electrolysis
- Extraction of Metals
- pH
- Titration
- Strong and Weak Acids
- Endothermic and Exothermic Reactions
- Rate of Reaction
- Catalysts
- Dynamic Equilibrium
- Carbon Compounds
- Crude Oil
- Life Cycle Assessment and Recycling
- The Earth and its Atmosphere
- The Greenhouse Effect
- Potable Water
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GCSE Chemistry (Combined) Eduqas Revision Content
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GCSE Chemistry (Combined) Eduqas - Core - Purity of Substance Content Preview
Core
Purity of Substance
Purity of Substance
Definition and Importance
- Purity refers to how free a substance is from other substances.
- In chemical terms, a pure substance contains only one type of element or compound.
- The purity of substances is important in a variety of fields such as medicine, manufacturing, and research.
Identifying Pure Substances
- A pure substance will always have definite physical and chemical properties such as boiling point, melting point, density, and solubility.
- Pure substances always melt and boil at specific temperatures because their microscopic structure is uniform.
- A pure substance's boiling point or melting point can be used to identify the substance, as these properties are unique to each substance.
Impure Substances
- Mixtures are considered impure substances as they contain two or more different substances not chemically combined together.
- For instance, air is a mixture of mainly nitrogen and oxygen gases.
- Impure substances have varying boiling points and melting points because their microscopic structure differs.
- As a result, they often melt or boil over a range of temperatures instead of a specific temperature.
Methods of Purity Check
- Melting Point Testing: The melting point of a substance is compared against its known standard value. The closer the test value is to the standard value, the purer the substance is likely to be.
- Boiling Point Testing: Similar to the melting point test, the boiling point of a substance can also be used to check its purity by comparing it against known values.
- Chromatography, in its various forms (paper, thin layer, gas etc.), is used to separate and identify different substances in a mixture. The distances moved by different substances up a chromatography paper or the time taken for substances to appear in a gas chromatograph can help identify and determine the purity of substances.
Purity in Industry
- In pharmaceuticals, it is vital that each drug contains the exact amount of pure substance stated to ensure it's safe and effective.
- In food production, the purity of substances such as additives and preservatives is significant for health and safety.
Question: Describe how you would use boiling point testing to check the purity of a substance.
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