Introduction
The nature of the world around us has been the subject of interest and speculation for thousands of years. The original chemistry concerned itself with observing and compiling data on the many substances that could be found free in nature or prepared by simple procedures such as heating. People working with such substances were known as alchemists (from the Arabic 'al quimia') and although much time and effort was put into the search for the philosopher's stone, there was also a great deal of useful information gathered.
The theories underlying the structure of matter waited until the eighteenth century when John Dalton made observations regarding the indivisible particles of matter, which he called atoms.
This section deals with the fundamental ideas needed to understand the nature of chemistry.
Structure 1.1.1 - Elements are the primary constituents of matter, which cannot be chemically broken down into simpler substances.
- Compounds consist of atoms of different elements chemically bonded together in a fixed ratio.
- Mixtures contain more than one element or compound in no fixed ratio, which are not chemically bonded and so can be separated by physical methods.
- Distinguish between the properties of elements, compounds and mixtures.
Guidance
Tools and links
- Tool 1 - What factors are considered in choosing a method to separate the components of a mixture?
- Tool 1 - How can the products of a reaction be purified?
- Structure 2.2 - How do intermolecular forces influence the type of mixture that forms between two substances?
- Structure 2.3 - Why are alloys generally considered to be mixtures, even though they often contain metallic bonding?
Structure 1.1.2 - The kinetic molecular theory is a model to explain physical properties of matter (solids, liquids and gases) and changes of state.
- Distinguish the different states of matter.
- Use state symbols (s, l, g, and aq) in chemical equations.
Guidance
- Names of the changes of state should be covered: melting, freezing, vaporization (evaporation and boiling), condensation, sublimation and deposition.
Tools and links
- Structure 2.4 - Why are some substances solid, while others are fluid under standard conditions?
- Structure 2 (all)
- Reactivity 1.2 - Why are some changes of state endothermic and some exothermic?
Structure 1.1.3 - The temperature, T, in Kelvin (K) is a measure of average kinetic energy Ek of particles.
- Interpret observable changes in physical properties and temperature during changes of state.
- Convert between values in the Celsius and Kelvin scales.
Guidance
- The kelvin (K) is the SI unit of temperature and has the same incremental value as the Celsius degree (°C).
Tools and links
- Reactivity 2.2 - What is the graphical distribution of kinetic energy values of particles in a sample at a fixed temperature?
- Reactivity 2.2 - What must happen to particles for a chemical reaction to occur?