C2.1 Purity and separating mixtures

• What is relative atomic mass?

  It is the mass of an atom compared to the mass of a carbon atom.
• How is relative formula mass calculated?

  By adding the relative atomic masses of all atoms in the chemical formula.
• What does a chemical formula indicate?

  It shows how many atoms of each element are present in a substance.
• What is the chemical formula for water?

  H₂O
• What is an empirical formula?

  An empirical formula shows the simplest whole-number ratio of atoms in a compound.
• How do you calculate an empirical formula from a compound's composition?

  By finding the highest common factor of the number of atoms of each element.
• What does 'pure' mean in the context of substances?

  'Pure' means a substance that has not been mixed with any other substance.
• How can melting points be used to determine purity?

  Pure substances have specific melting points, while impure substances have lower and broader melting points.
• Can mixtures be useful?

  Yes, mixtures can be useful in various applications, such as alloys in metals.
• What is an example of a mixture that is useful?

  An alloy, such as bronze, which is a mixture of copper and tin.
• What happens when a substance dissolves?

  A soluble substance breaks down into smaller particles and spreads throughout the solvent.
• How does filtration work?

  Filtration separates solids from liquids using a barrier that allows only the liquid to pass through.
• How does crystallization work?

  Crystallization occurs when a solution cools and solute particles form solid crystals.
• What is the purpose of distillation?

  Distillation is used to separate components of a mixture based on their boiling points.
• How does fractional distillation differ from simple distillation?

  Fractional distillation separates mixtures with closer boiling points, while simple distillation is for mixtures with significantly different boiling points.
• How does chromatography work?

  Chromatography separates components of a mixture based on their movement through a stationary phase.
• What is the role of the stationary phase in chromatography?

  The stationary phase is the material that does not move and allows the components to separate based on their affinity for it.
• What is gas chromatography used for?

  Gas chromatography is used to separate and analyze compounds that can be vaporized without decomposition.
• How can you tell if a substance is pure using chromatography?


  If a substance produces a single spot on the chromatogram, it is considered pure.
• What is the significance of the Rf value in chromatography?

  The Rf value indicates the relative distance traveled by a compound compared to the solvent front.
• How can two-dimensional chromatography improve separation?

  Two-dimensional chromatography allows for separation in two different directions, enhancing the resolution of components.
• How can gas chromatography be used to analyze food samples?

  Gas chromatography can identify volatile compounds in food samples, providing information about their composition.
• Why might a technician's copper sample not be pure?

  It may contain impurities from the environment or during the handling process.
• What is the importance of checking the purity of substances?

  Checking purity ensures that substances meet required standards for safety and effectiveness.
• How can mixtures be separated using two-dimensional chromatography?

  By applying the mixture to a stationary phase and allowing it to move in two directions, separating components based on their properties.
• What does the data in a gas chromatogram indicate?

  The data shows the presence and concentration of different compounds in the sample analyzed.
• How can the purity of a substance affect its properties?


  Impurities can alter the physical and chemical properties of a substance, affecting its performance and safety.
• Why is it important to use proper techniques when separating mixtures?

  Proper techniques ensure accurate results and prevent contamination of the samples.
• What is the role of a technician in checking the purity of substances?


  A technician is responsible for performing tests and analyses to determine the purity of substances.
• How can contamination affect the results of an experiment?

  Contamination can lead to inaccurate results and misinterpretation of data.
• What is the significance of using a control in experiments?


  A control allows for comparison and helps to validate the results of the experiment.
• How can the results of chromatography be used in real-world applications?

  Chromatography results can be used in quality control, forensic analysis, and environmental testing.
• Why is it important to understand the properties of substances when conducting experiments?

  Understanding properties helps in selecting appropriate methods for separation and analysis.
• How does the choice of separation method depend on the properties of the substances involved?

  The choice of separation method depends on factors like solubility, boiling point, and particle size.
• What is the importance of safety precautions in laboratory work?

  Safety precautions prevent accidents and ensure a safe working environment.
• How can the results of an experiment be communicated effectively?

  Results can be communicated through reports, presentations, and discussions.
• Why is it important to repeat experiments?

  Repeating experiments helps to verify results and ensure reliability.
• How can technology aid in the analysis of substances?

  Technology can provide advanced tools and methods for accurate analysis and data collection.
• What is the role of collaboration in scientific research?

  Collaboration allows for sharing of knowledge and resources, enhancing the quality of research.
• How can scientific research contribute to society?

  Scientific research can lead to advancements in technology, medicine, and environmental protection.