2013-2-27 Phase A quantity of matter that is homogeneous throughout in both chemical composition and physical structure. Homogeneity in physical structure means that the matter is all solid,or all liquid,or al vapor (gas). Examples: The air we breathe is a gas phase consisting of a mixture of different gases. Drinking water with ice cubes contains two phases of water:liquid and solid. Vinegar and olive oil salad dressing contains two different liquid phases. 3-5 Pure Substance A substance that is uniform and invariable in chemical composition. A pure substance can exist in more than one phase,but its chemical composition must be the same in each phase. Examples: Drinking water with ice cubes can be regarded as a pure substance because each phase has the same composition. A fuel-air mixture in the cylinder of an automobile engine can be regarded as a pure substance until ignition occurs 3-6 32013-2-27 3 Phase ►A quantity of matter that is homogeneous throughout in both chemical composition and physical structure. ►Homogeneity in physical structure means that the matter is all solid, or all liquid, or all vapor (gas). ►Examples: ►The air we breathe is a gas phase consisting of a mixture of different gases. ►Drinking water with ice cubes contains two phases of water: liquid and solid. ►Vinegar and olive oil salad dressing contains two different liquid phases. 3-5 ►Examples: ►Drinking water with ice cubes can be regarded as a pure substance because each phase has the same composition. ►A fuel-air mixture in the cylinder of an automobile engine can be regarded as a pure substance until ignition occurs Æ Pure Substance 3-6 ►A substance that is uniform and invariable in chemical composition. ►A pure substance can exist in more than one phase, but its chemical composition must be the same in each phase