C2.1.1 Pure Substances and Mixtures

• A mixture is a combination of two or more pure substances that are not chemically bonded
• Give an example of a pure substance.

  Water
• How are mixtures classified?

  Homogeneous or heterogeneous
• Pure substances have a fixed and definite chemical composition
• Pure substances have a sharp, single melting/boiling point.


  True
• What type of chemical composition do mixtures have?

  Variable
• The chemical composition of a pure substance is fixed and definite
• What is the chemical composition of a mixture?

  Variable
• What is the key difference between pure substances and mixtures?

  Fixed vs variable composition
• Name an example of a pure substance that is an element.

  Oxygen
• What is the chemical formula for glucose?

  C6H12O6
• What is a mixture defined as?

  Two or more pure substances not chemically bonded
• Pure substances have a sharp, single melting point.

  True
• The chemical composition of a pure substance is fixed and definite
• Steps to separate a mixture using physical means

  1️⃣ Identify the components of the mixture

  2️⃣ Choose a suitable separation method (e.g., filtration or distillation)

  3️⃣ Apply the separation method

  4️⃣ Collect the separated components
• Mixtures have a variable chemical composition and variable physical properties
• Give examples of compounds that are pure substances.

  Water, carbon dioxide, salt
• The components in a mixture retain their original chemical nature when separated by physical means.


  True
• What is the key difference between homogeneous and heterogeneous mixtures?

  Uniform vs. non-uniform composition
• What is a pure substance defined as?

  Single element or compound
• Pure substances have a fixed chemical composition.


  True
• Examples of mixtures include air and milk
• A pure substance has a fixed chemical composition.


  True
• What are the physical properties of a pure substance?

  Consistent and predictable
• A mixture is a combination of pure substances that are not chemically bonded
• How can mixtures be separated without changing the chemical nature of their components?

  Physical means
• Mixtures have a sharp, single melting/boiling point.

  False
• The components in a mixture can be separated by chemical reactions.

  False
• Mixtures do not have a sharp, single melting or boiling point
• Carbon dioxide is a compound with the formula CO2
• Mixtures have a variable chemical composition.


  True
• A pure substance has a fixed chemical composition
• What type of chemical composition do mixtures have?

  Variable
• Mixtures have a single, sharp melting point.

  False
• What are the physical properties of pure substances like?

  Consistent and predictable
• Give examples of elements that are pure substances.

  Hydrogen, oxygen, gold
• Match the type of mixture with its example:

  Homogeneous mixture ↔️ Air

  Heterogeneous mixture ↔️ Sand and water

  Alloy ↔️ Brass
• Homogeneous mixtures have a uniform composition