Science Quiz: Mixtures and Compounds

Mixtures

• Mixtures can be separated into multiple pure substances using physical methods like filtration, sublimation, or distillation.
• Components are the pure substances that make up a mixture.
• Common examples of naturally occurring mixtures include air, water, seawater, soil, rocks, and minerals.
• Living organisms, like plants and animals, and food are complex mixtures.
• Many human-made substances, including milk and blood, are mixtures.

Compounds

• Compounds are formed when elements combine in a fixed ratio by mass or number of atoms.
• Compounds can only be broken down into their constituent elements through chemical reactions, not physical methods.
• Elements combine in a fixed proportion, like the 2:1 ratio of hydrogen to oxygen by mass in water.
• Compounds have properties distinct from the elements they are composed of. For example, water has different properties than hydrogen and oxygen.
• The mass of a compound is equal to the sum of the masses of its constituent elements.

Characteristics of Compounds

• Chemical Decomposition: Compounds can only be broken down into their constituent elements by chemical means.
• Fixed Proportion: Elements combine in a fixed proportion by mass or number of atoms when forming a compound.
• Mass Ratio: Elements combine in a set mass ratio. For example, the mass ratio of hydrogen to oxygen in water is 1:8.
• Different Properties: The properties of a compound are different from the properties of the elements that compose it.

Examples of Compounds

• Sodium chloride (NaCl)
• Calcium oxide (CaO)
• Calcium chloride (CaCl₂)
• Zinc chloride (ZnCl₂)
• Hydrogen chloride (HCl)
• Sulphuric acid (H₂SO₄)
• Nitric acid (HNO₃)
• Sodium sulphate (Na₂SO₄)
• Sodium hydrogencarbonate (NaHCO₃)
• Plaster of Paris (CaSO₄ H₂O)

Examples of Reactions

• Hydrogen + Oxygen --> Water
• Carbon + Oxygen --> Carbon dioxide