Unit 7, Lesson 4 Solutions Element – purest form of a substance

COMPOUNDS A compound is a substance made of two or more elements chemically combined in a definite ratio or proportion. Examples: Carbon Dioxide gas is a compound made up of Carbon and Oxygen. Water is a compound made up of oxygen and hydrogen.

Compounds can be broken down into simpler substances *Compounds can be broken down into simpler substances. *They can only be broken down through a chemical change. Ex: If an electric current is passed through melted table salt, the elements sodium and chlorine are produced.

MIXTURES A mixture is made from two or more substances (elements or compounds) that are NOT chemically combined. Most matter occurs in mixtures.

Mixtures differ from compounds: The substances in a mixture keep their individual properties. Mixtures can be physically separated. Mixtures do not need to be combined in a definite ratio. Example: soil has particles of sand, tiny bits of clay, and pieces of decaying plants. If you were to grab 2 handfuls of soil would they be made up of the same amount of clay, sand, and decaying plant matter?

Common Techniques for Separating Mixtures Distillation: Separates a mixture based on boiling points of the components. Magnet Centrifuge: a machine that separates Mixtures according to the densities of the components.

Which is a mixture and which is a compound? Chex mix Table salt Water Muddy water Carbon dioxide

SOLUTIONS A mixture in which two or more substances are are so completely blended that it looks to be a single substance Described as homogeneous mixtures because they have the same appearance and properties throughout. Examples: salt water, lemonade, Kool Aid

Solutions have two parts the solute and the solvent. Solute – substance that is being dissolved in a solution. Solvent – substance that does the dissolving When 2 liquids or 2 gases form a solution, the substance with the greater volume is the solvent.

Solutions Can Be: Gas dissolved in a gas * air – oxygen is dissolved in nitrogen Gas dissolved in a liquid * Coke - carbon dioxide dissolved in soda A solid dissolved in a liquid * Salt Water -salt dissolved in water A liquid dissolved in another liquid * vinegar – acetic acid dissolved in water A solid dissolved in another solid * bronze - tin dissolved in copper

Suspensions Mixture in which large particles are mixed into a liquid or gas. The particles are large enough that they settle out or can be filtered out. Described as heterogeneous (different components) Insoluble (do not dissolve) Particles settle to the bottom when allowed to sit undisturbed. Examples – muddy water, Italian salad dressing, snow globe

Colloids Mixture that contains medium sized particles that are dispersed throughout but are not heavy enough to settle out and cannot be filtered. Particles are fairly small and well mixed Examples – mayonnaise, stick deodorant, gelatin and whipped cream

Concentration = mass of solute volume of solvent The measure of the amount of solute dissolved in a solvent To calculate concentration use the equation: Concentration = mass of solute volume of solvent

A dilute solution contains a small amount of solute. A concentrated solution contains a large amount of solute. A saturated solution contains all the solute that a solution can hold at a given temperature and pressure.

Solubility The ability to dissolve in a given amount of solvent at a certain temperature and pressure. Two factors that affect solubility are temperature and pressure. An increase in temperature helps dissolve solutes more quickly and lets you dissolve a greater amount. In a gas, solubility is increased with higher pressure.   In a gas, solubility is decreased with lower pressure. Pressure changes do not affect the solubility of solids and liquids.

Factors that affect how fast a solid will dissolve: Stirring or shaking the solution Heating the solution Crushing the solute before adding it to the solvent Each method helps the solid particles separate and spread out among the liquid particles.