Introduction to the particulate nature of matter and chemical change

Nature of science:

Making quantitative measurements with replicates to ensure reliability—definite and multiple proportions. (3.1)

• Atoms of different elements combine in fixed ratios to form compounds, which have different properties from their component elements.
• Mixtures contain more than one element and/or compound that are not chemically bonded together and so retain their individual properties.
• Mixtures are either homogeneous or heterogeneous.

Applications and skills:

• Deduction of chemical equations when reactants and products are specified.
• Application of the state symbols (s), (l), (g) and (aq) in equations.
• Explanation of observable changes in physical properties and temperature during changes of state.

Guidance:

• Balancing of equations should include a variety of types of reactions.
• Names of the changes of state—melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and deposition—should be covered.

• Chemical symbols and equations are international, enabling effective communication amongst scientists without need for translation.
• IUPAC (International Union of Pure and Applied Chemistry) is the world authority in developing standardized nomenclature for both organic and inorganic compounds.

Theory of knowledge:

• Chemical equations are the “language” of chemistry. How does the use of universal languages help and hinder the pursuit of knowledge?
• Lavoisier’s discovery of oxygen, which overturned the phlogiston theory of combustion, is an example of a paradigm shift. How does scientific knowledge progress?

Utilization:

• Refrigeration and how it is related to the changes of state.
• Atom economy.
• Freeze-drying of foods.

• The term “latent heat” is not required.
• Names and symbols of elements are in the data booklet in section 5.

• Syllabus and cross-curricular links:
• Topic 4.1—deduction of formulae of ionic compounds
• Topic 5.1—enthalpy cycle reaction; standard state of an element or compound
• Topic 6.1—kinetic theory
• Topic 8.2—neutralization reactions Topic
• 0.2—combustion reactions Option
• A.4—liquid crystals

Aims:

• Aim 8: The negative environmental impacts of refrigeration and air conditioning systems are significant. The use of CFCs as refrigerants has been a major contributor to ozone depletion.