Elements, Compounds and Mixtures Section 3 - Mixtures pp. 98-105

Mixtures A combination of two or more pure substances that are not chemically combined. substances held together by physical forces, not chemical No chemical change takes place Each item retains its properties in the mixture They can be separated physically Chem4kids.com

MIXTURES Components of a mixture do not have a definite ratio. Air is a mixture that is composed mostly of nitrogen and oxygen. It also contains carbon dioxide and water vapor. On some days there is more water vapor in the air than on others.

METHODS OF SEPARATING MIXTURES Distillation Using a magnet and/or “picking parts out” by hand Centrifuging Filtration

DISTILLATION A method of separating a mixture based on the boiling points of the components

USING A MAGNET OR REMOVING UNWANTED THINGS BY HAND Picking out iron filings Picking out unwanted things by hand

CENTRIFUGING A centrifuge is a machine that separates mixtures according to their densities

FILTRATION When you filter a substance, first you must mix it with another compound (like water). Then you pour the mixture through a filter. The solid is trapped by the filter.

MIXTURES VS. COMPOUNDS MIXTURES COMPOUNDS Components are elements, compounds, or both Components are elements Components keep their original properties Components lose their original properties Separated by physical means Separated by chemical means Formed using any ratio of components Formed using a set mass ratio of components

TYPES OF MIXTURES Solutions Suspensions Colloids

SOLUTIONS A mixture of two or more substances that are evenly distributed amongst each other. Solutions are also called homogeneous mixtures because they have the same appearance and properties throughout the mixture. The particles in a solution are extremely small. Some examples of solutions are salt water, tea and coffee

SOLUTIONS (Vocabulary Terms) Dissolving: the process in which particles of substances separate and spread evenly throughout the mixture. Solute: the substance that is dissolved; a solute is soluble (able to be dissolved) in a solvent Solvent: the substance that does the dissolving. A substance that is insoluble (unable to dissolve) forms a mixture that is not a solution.

SOLUTIONS (Vocabulary Terms) Concentration – a measure of the amount of solute dissolved in a solvent. A solution can be concentrated (when there is more solute than solvent) or dilute (when there is more solvent than solute). Kool-Aid that doesn’t have enough water in it is very sweet and is concentrated; Kool-Aid that has too much water in it is dilute

SOLUTIONS (Vocabulary Terms) A saturated solution is one that contains all the solute it can hold at a given temperature. An unsaturated solution is a solution that contains less solute than it can hold at a given temperature. When you increase the temperature of a solution you can add more solute, supersaturating the solution.

Water is known as the universal solvent:

Air is a solution of oxygen and other gases dissolved in nitrogen

Alloys are Mixtures Alloys are solid solutions of metals or nonmetals dissolved in metals.

Alloys examples) Stainless steel is a mixture of iron and chromium. Brass is an alloy of copper and zinc.

Types of solutions Gas Air (oxygen in nitrogen) Liquid Solute Solvent Example Gas Air (oxygen in nitrogen) Liquid Soda water (carbon dioxide in water) Solid Ocean water (salt in water) Solid Brass ( copper and zinc) .

Suspensions Suspensions are mixtures ( liquid or gas) in which the particles are larger than ones found in solution. They are insoluble and will settle out. They are often described as heterogeneous mixtures because the different components are easily seen. Examples: Italian salad dressing, muddy water, snow globe, blood They also do not transmit light they scatter light or block light. A suspension can be separated by passing it through a filter.

COLLOIDS A mixture in which particles are dispersed throughout but not heavy enough to settle out. The particles in a colloid are relatively small and are fairly well mixed. Particles in a colloid can scatter light, but cannot be separated by filtration.

Examples of Colloids milk, mayo, cheese, whipped cream, deodorant, fog, gelatin, smoke, toothpaste detergents They are heterogeneous mixtures

Is it uniform throughout? If the answer is no, the matter is a heterogeneous mixture. Does not appear to be the same throughout. Particles are large enough to be seen and to be separated from the mixture.

Examples of heterogeneous mixtures Sand and pebbles Chicken noodle soup Granite Oil and water

Is it uniform throughout? If the answer is yes, the matter is homogeneous (looks the same throughout)

Homogeneous Mixtures A mixture that appears to be the same throughout. The particles that make up the mixture are very small and not easily recognizable.