Presentation on theme: "Mixtures Salt water Coffee Salad dressing Soda Soup Fog."— Presentation transcript:
Mixtures Salt water Coffee Salad dressing Soda Soup Fog
A mixture is material made up of two or more substances that are not chemically combined. Each substance in the mixture keeps its own properties. Ex. salt water, pizza Mixtures can be separated with physical processes. These include filtering, separating by distillation (salt water) or machines such as the centrifuge (blood). Separation can also occur using density, melting, freezing, and magnetism.
Mixtures do not always contain the same amounts of different substances. (They do not have set ratios.) MixturesCompounds can be made of elements, compounds, or both made of elements keep their original propertieslose original properties separated by physical meansseparated by chemical means formed using any ratio of components formed using a set mass ratio of elements (like H 2 O)
A solution is a mixture that appears to be a single substance but is made of particles of two or more substances that are evenly mixed. The particles are so small they cannot be seen and they never settle out. Another name is a homogeneous mixture because they have the same appearance and properties throughout. Ex. salt water, vinegar, cake, iced tea, stainless steel, brass.
The solute is the substance being dissolved (like sugar in coffee). The solvent is the substance in which the solute is dissolved (coffee). Salt is the solute and water is the solvent in salt water.
Concentration is a measure of the amount of solute dissolved in a solvent. Concentration can be expressed in grams of solute per milliliter of solvent. Solutions can be described as concentrated (lots of solute) or dilute (a little of solute).
A saturated solution contains all the solute it can at a given temperature. An unsaturated solution contains less solute than it can hold at a given temperature. More solute can be dissolved into an unsaturated solution. A supersaturated solution is forced to contain more solute than its normal saturation level. Solutions can be saturated, unsaturated or supersaturated.
Solubility is the amount of solute needed to make a saturated solution given the amount of solvent at a given temperature. Solubility is usually expressed in grams per 100 mL of solvent. The solubility of KNO 3 is 250 g at 100°C.
There are three methods to help solids dissolve faster including: mixing by stirring or shaking, heating, and crushing. Gases dissolve faster when they are cooled.
A suspension is a mixture where particles are throughout the liquid but are large enough to settle out. Ex. muddy water, salad dressing, some liquid medicines (“shake before using”). Suspensions are heterogeneous mixtures because the different parts can be easily seen. The particles are insoluble so they do not dissolve in liquid or gas.
The particles of a suspension are large and scatter or block light so they are difficult to see through. If it sits undisturbed, the particles will settle out like a snow globe. A suspension can separated with a filter.
A colloid is a heterogeneous mixture in which particles are spread throughout but are not heavy enough to settle out. The particles are relatively small and fairly well mixed. Ex. fog, jello, milk, smoke, mayonnaise, stick deodorant. The particles of a colloid are smaller than a suspension, but these particles still scatter a beam of light when shined through. A colloid cannot be separated with a filter.
The Tyndall effect is the scattering of light by particles in a mixture. The Tyndall effect can be seen in all colloids. (Remember that colloids have invisible particles that never settle out.) Both the yellow and red liquids at left look all the same. The yellow solution does NOT scatter the light, but the red colloid scatters the light. Fog scatters light.
Smog is a form of air pollution. Smog is a colloid of small, invisible pieces of solid materials mixed with the gases that make up air. Smog has many natural causes like forest fires, volcanic eruptions, wind and dust. The major cause of smog today is the unburned particles in automobile exhaust. Other causes of smog: gasoline stations & industrial plants hair sprays & spray paints wood-burning stoves & fireplaces
Solubility Graph Notes Remember: on the line – saturated below the line – unsaturated above the line - supersaturated 1) How many grams of sodium chlorate dissolves at 60ºC? 160 g 2) At what temperature does 40g of sodium chloride dissolve?80ºC 3) Would 120g of potassium bromide at 80ºC form a saturated, unsaturated or supersaturated solution? supersaturated 4) Would 80g of sodium nitrate at 20ºC form a saturated, unsaturated or supersaturated solution? unsaturated