Mixtures

mixture -a mixture is a combination of two or more substances that ARE NOT chemically combined (they DO NOT form a compound!) EXAMPLE: Pizza - the crust, tomato sauce, cheese, and toppings do not react chemically with each other -each substance keeps its identity -in some (like the pizza) you can see the individual substances -in others (like salt water) you can't -CAN be broken down, or separated, by physical change -some easier to separate than others COMMON SEPARATION TECHNIQUES  Properties of Mixtures

Distillation – separates a mixture based on the boiling points of the components Magnetism - a magnet can be used to separate iron from a mixture Centrifuge - a machine that spins and separates mixtures according to the densities of their components Multi-step Separation - Sometimes more than one step needed to separate mixtures (other substances may even need to be added) COMMON SEPARATION TECHNIQUES

-no definite ratio of components -doesn't matter how much of each substance there is, because they don't combine chemically EXAMPLE: Granite - composed of: quartz, mica,& feldspar different concentrations of each mineral affect the color of the sample, but it is still granite because it is a mixture of those same 3 minerals Mixtures vs. Compounds Mixtures: components are elements, compounds, or both components keep original properties separated by physical means no set ratio of components Compounds: components are elements components lose original properties separated by chemical means set mass ratio of components

Solutions solution -a solution is a mixture that appears to be a single substance but is composed of particles of 2 or more substances that are distributed evenly amongst each other -solutions are homogeneous (same properties and appearance throughout) solute -solute (substance that is dissolved) solvent -solvent (substance in which the solute is dissolved) -solutions may be: solid (alloys like steel or brass) liquid (like saltwater or antifreeze) gas (like the air we breathe) -see the chart on page 245

Properties of Solutions -tiny particles: particles are so small that they never settle out, cannot be filtered, and do not scatter light concentration -concentration : measure of how much solute is dissolved in a solvent (expressed in grams per milliliter) -more solute = concentrated -less solute = dilute - saturated : a solution that holds all the solute it can at a certain temperature -unsaturated :a solution that holds less than it can at a certain -temperature solubility -solubility : the amount of solute needed to make a saturated solution using a given amount of solvent at a certain temperature (expressed in grams of solute per 100 ml of solvent)

Rate of Dissolving -many factors affect how fast a solid dissolves into a liquid -to speed up dissolving: Mixing - stirring or shaking causes particles of solute to break apart and spread out more quickly Heating - adds energy, causing particles to move more quickly which allows solvent particles to separate solute particles and spread them out Crushing - crushing the solute increases contact between it and the solvent so the particles mix more quickly

Suspensions suspension -a suspension is a mixture in which particles of a material are dispersed throughout a liquid or gas but are large enough to settle out -particles are insoluble (do not dissolve) -called heterogeneous (components can easily be seen) -particles are large and scatter or block light -particles too heavy to remain suspended, so they settle to the bottom (unless shaken or stirred) -can be separated by passing through a filter EXAMPLES: liquid antacid, salad dressing, snow globes

Colloids colloid -a colloid : mixture in which the particles are dispersed throughout but are not heavy enough to settle out -particles are fairly small and well mixed -solids, liquids, and gases can be used to make them -particles are small, but large enough to scatter light -cannot be separated by filtration (particles small enough to pass through filter) EXAMPLES: gelatin (jell-o), whipped cream, butter, mayonnaise, stick deodorant