S1.1 Particulate Nature of Matter

• 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.

• The kinetic molecular theory is a model to explain physical properties of matter (solids, liquids and gases) and changes of state.

• The temperature, T, in Kelvin, is a measure of the average kinetic energy of particles.

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 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?

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?