How can homogeneous and heterogeneous mixtures be 1. classified? 2. separated?
1. HETEROGENEOUS MIXTURE 2. COLLOID 3. EMULSION 4. SUSPENSION 5. FILTRATION 6. TYNDALL EFFECT 7. HOMOGENEOUS MIXTURE 8. SOLUTION 9. SOLUTE 10. SOLVENT 11. MISCIBLE LIQUID 12. DISTILLATION
Cannot be decomposed into simpler substances by chemical change 114 known elements 2 more predicted
Two or more elements combined with chemical bonds Can be decomposed into simpler substances Chemical changes needed
2+ substances NOT chemically combined. Variable composition: made of more than 1 substance Components retain their characteristic properties Separate using physical change
Variable composition English: made of a variety of substances Components retain their characteristic properties English salt is salt, water is water May be separated into pure substances by physical methods see next slide
Distill Evaporate Let them settle/use centrifuge Filter Chromatography
Same throughout - texture, color, etc. Components indistinguishable Separate w/physical change Example: sweetened drinks
Smallest particle size molecular/atomic size Solute = what is dissolving (e.g. salt) Solvent = what the solute is dissolving in, which is usually a fluid- liquid or gas (e.g. water) Solvent pulls apart the molecules of the solute. Does not usually separate on its own because the solvent holds the particles of the solute tightly (evaporation, distillation)
Water dissolves many substances Ionic or polar covalent
Solids in solids - Alloys e.g. brass Gases in gases air is a homogeneous mixture of gases Gases in liquids carbon dioxide in water (carbonated drinks)
Solutions made from liquids Mix totally Example: water and rubbing alcohol Separate via distillation Some liquid solutions do not contain water, e.g. petroleum
Homogeneous mixture Look like solutions. A substance trapped inside another substance. Particles about size of bacteria (not visible w/out microscope) Tyndall effect. Separated via distillation/evaporation For example: shaving cream, latex
Boil the liquid, forming a vapor, then condense vapor into liquid again
Heat solution, the liquid evaporates the solid left behind. Example: separating salt from water
1.Emulsion 2.Suspension 3.Heterogeneous
Particles broken up smaller than mud, larger than bacteria Need to be centrifuged E.g. homogenized milk, mayonnaise
Solid mixed with liquid Settles by itself (e.g. orange juice, mud in water) Separated via filtration Like a snow-globe, unhomogenized milk Particles are size of fine mud particles
Incompatible substances (no dissolving) Separate easily on their own (e.g. by density) Gravitational pull only (settling). Examples: Water and Oil, oil and salt
Centrifuge, natural settling
Your assignment Assignment Solution Heterogeneous mixture Colloid Define Two or more substances which do not dissolve. Repel each other. Example Lava lamp, oil and vinegar, coffee (before you filter it) How are they separated? How is it similar to A heterogeneous mixture? Filtration A colloid? A solution? don t dissolve; big particles
1. Why is water called the universal solvent? 2. How do substances dissolve? 3. How do solutes affect a solution?
1. Polar compound 2. Nonpolar compound 3. Hydrogen bond
Uneven distribution of charge Ionic compounds polar Some molecular (covalent) compounds too Water polar covalent compound Water dissolves polar compounds because water molecules attract both positive and negative ions
Polar water molecules pull ionic crystals apart, as shown below. The partially negative oxygen atoms of water molecules attract the positively charged sodium ions. The partially positive hydrogen atoms of water molecules attract the negatively charged chloride ions.
Dissolving depends on the forces between particles. The forces between the solvent molecules and the particles of the substances must be greater than the force between the particles in the crystal. Water dissolves many NONPOLAR compounds. Water forms hydrogen bonds with NONPOLAR molecular compounds such as sugar. hydrogen bond: the intermolecular force occurring when a hydrogen atom that is bonded to a highly electronegative atom of one molecule is attracted to two unshared electrons of another molecule
Like dissolves like. A solvent will dissolve substances that have molecular structures that are like the solvent s structure. Nonpolar compounds usually will not dissolve in water. nonpolar: describes a molecule in which the centers of positive and negative charge are not separated Nonpolar solvents are used to dissolve nonpolar materials.
Why do substances dissolve? The energy transferred from the solvent to the solute, as well as the attractive forces between the solvent and solute molecules, causes molecules at the surface of the crystal to dissolve.
Solutes with a larger surface area dissolve faster. More solute particles are exposed to the solvent. Stirring or shaking a solution helps the solute dissolve faster. Dissolved solute particles diffuse throughout the solution faster. More solute particles can dissolve. Solutes dissolve faster when the solvent is hot. Collisions occur between solute and solvent particles more frequently and with more energy.
Solutes affect the physical properties of a solution. Solutes increase the boiling point of a solution. If you dissolve salt in water, it will boil at a higher temperature. Solutes lower the freezing point of a solution. The coolant mixture of ethylene glycol and water keeps a car s radiator fluid from freezing in winter.
Polar-polar Water-salt Ethanol-ink Nonpolar-nonpolar Oil paint + nonpolar solvent
Surface area Stirring/shaking Heat
Solutes affect the physical properties of a solution. Solutes increase the boiling point of a solution. If you dissolve salt in water, it will boil at a higher temperature. Solutes lower the freezing point of a solution. The coolant mixture of ethylene glycol and water keeps a car s radiator fluid from freezing in winter.
1. What is solubility? 2. How do saturated solutions react when more solute is added? 3. What is concentration, and how can it be calculated?
Solubility Concentration Saturated solution Unsaturated solution Supersaturated solution Molarity
What is solubility? The solubility of a substance is the maximum mass of a solute that can dissolve in 100 g of solvent at a certain temperature and standard atmospheric pressure. solubility: the ability of one substance to dissolve in another at a given temperature and pressure
Different substances have different solubilities.
How much of substance is in a solution? To express how much of a substance can dissolve in a solvent, you need to use the concentration. Concentration: the amount of a particular substance in a given volume of a mixture, solution, or ore A concentrated solution has a large amount of solute. A dilute solution has only a small amount of solute.
What happens when you add more solute to a saturated solution? In a saturated solution, the dissolved solute is in equilibrium with undissolved solute. So, if you add more solute, it just settles to the bottom of the container. saturated solution: a solution that cannot dissolve any more solute under the given conditions
Unsaturated solutions can become saturated. unsaturated solution: a solution that contains less solute than a saturated solution does and that is able to dissolve additional solute Heating a saturated solution can dissolve more solid. The solubility of most solutes increases with temperature.
supersaturated solution: a solution that holds more dissolved solute than is required to reach equilibrium at a given temperature. To make a supersaturated solution, you raise the temperature of a solution, dissolve more solute, then let the solution cool again.
Temperature and pressure affect the solubility of gases. Gaseous solutes are less soluble in warmer water. Example: Soda goes flat quickly at room temperature. Gases are more soluble under higher pressure. Example: When a can of soda is opened, carbon dioxide gas that had been dissolved in the soda bubbles out of solution.
How do you describe how much of a solute is in a solution? One of the most common ways of expressing the concentration of solution is molarity. Molarity: a concentration unit of a solution expressed in moles of solute dissolved per liter of solution. molarity = moles of solute, or M mol liters of solution L
Concentration = mass molar mass volume M = Grams g/mol Liters OR M = mol liters Example: What is the concentration of a solution which contains 36 moles of magnesium carbonate in 0.1 liters? 36 moles 0.1 liters = 360 M
Moles = Concentration x volume mol = M x L Example: How many moles of hydrochloric acid are in 0.300 liters of a 2 M solution? Moles = 2M x 0.300 liters = 0.6 moles
Mass = Concentration x volume x molar mass g = M x L x g/mol Example: How many grams of Copper (II) sulfate 5H 2 O are required to make 0.200 L of a 1M solution? The molar mass of Copper (II) sulfate 5H 2 O is 249.72 g/mol.
1. Calculating Molarity 1. M = mol L 2. M = g g/mol L 2. Calculating Volume 1. L = M x mol 2. L = g x g/mol 3. Calculating Moles 1. mol = M x L 4. Calculating Mass 1. g = M x L x g/mol