Solutions and mixtures

Quick Review An element is a substance made up of atoms of one kind. A molecule is formed when atoms of the same elements combine. Two atoms of oxygen combine to form a molecule of oxygen [O2] A compound is formed when atoms or molecules of different elements combine chemically. Hydrogen and oxygen are combined in a fixed proportion of 2:1 to form the compound water [H2O]. Mixtures are two or more substances that are mixed together but not chemically joined.

Pure vs. Mix A pure substance: cannot be separated into 2 or more substances by physical means has uniform composition throughout the whole sample   A mixture: can be separated into 2 or more substances by physical or mechanical means displays the properties of the pure substances making it up its composition can be varied by changing the proportion of pure substances making it up heterogeneous substances, ones with non-uniform composition throughout the sample, are always mixtures

Mixtures When a mixture’s components are easily recognizable, such as pizza, it is called a heterogeneous mixture. In a homogeneous mixture such as chocolate milk, the component particles cannot be distinguished, even though they still retain their original properties.

More on mixtures Homogeneous – particles distributed evenly; the same throughout Heterogeneous – PARTICLES not evenly distributed; NOT THE SAME throughout

Type of Mixture Example gas in gas The atmosphere is a mixture of gases, mostly nitrogen and oxygen. liquid in liquid Wine is a mixture of mostly ethanol and water. solid in solid Alloys, such as brass, are made up of a mixture of metals. gas in liquid Soft drinks, such as cola, are mixtures of mainly carbon dioxide gas and water. solid in liquid Sea Water is a mixture of salts dissolved in water. solid in gas Smoke is mixture of tiny solid particles in atmospheric gases.

Solution aka Homogenous Mixture Solutions are composed of one or many solute(s) and only 1 solvent Solute: substance that dissolves into the solvent Solvent: substance that dissolves the solute(s)

A solution can exist in any of the 3 states of matter: (solid, liquid or gas) Solid Solutions ex: brass = copper + zinc This is called an alloy. (solvent) (solute) Gas Solutions ex: air = nitrogen + oxygen + argon + carbon dioxide (solvent) (solutes) Liquid Solutions ex: vinegar = acetic acid + water (solvent) (solute)

Compounds vs Mixtures Mixtures Compounds Combine chemically forming molecules Not chemically combined Combine in set proportions Can combine in any proportion Separated chemically Separated physically