Unit: Chemical Interactions Chapter 8: Solutions When substances dissolve to form solutions, the properties of the mixture change. 8.1: A solution is a type of mixture 8.2: The amount of solute that dissolves can vary 8.3: Solutions can be acidic, basic, or neutral 8.4: Metal alloys are solid mixtures

8.1: A solution is a type of mixture Review / warm-up What are their chemical formulas? What are the elements? Which is an ionic compound and which is a covalent compound? Are the properties of each compound the same/different than the atoms/elements that form them? What is the different in how these compounds are held together? NaCl CO2 Sodium Chlorine Carbon Oxygen NaCl, CO2 Different An ionic compound is held together by the attraction of oppositely charged ions; a covalent compound its held together by the sharing of pairs of electrons between two atoms C Na Cl O O animation

8.1 A solution is a type of mixture P111 p water, cups, spoon, salt, flour – which substances dissolve in water? (observe after 30 minutes) The salts dissolved, the flour did not (salt disappeared, flour clouded the water)

The parts of a solution are mixed evenly 8.1: A solution is a type of mixture The parts of a solution are mixed evenly Mixture: a combination of substances – ex: fruit salad, chili Can physically separate ingredients because they are not chemically changed – still the same substances If a mixture is so completely blended together… The ingredients canNOT be separated and identified as different substances Solution: a type of mixture, called a homogeneous mixture “same throughout” (“well-mixed”) All portions of the the mixture have the same properties Sand + Water  Sand sinks to the bottom ; Solution? Sugar + water  sugar is dispersed throughout; Solution? Other common solutions: seawater, gasoline, liquid part of blood

Solutes and Solvents – components of a solution 8.1: A solution is a type of mixture Solutes and Solvents – components of a solution Solutions – have a definite composition Solute – a substance that is dissolved to make a solution When it dissolves, it separates into individual particles It is dissolved into the… Solvent – a substances that dissolves a solute Most common: water Others – ex: turpentine, soaps - to remove oils After the solute dissolves and separates into individual particles, it is not possible to identify the solute and solvent as different substances Ex: Salt – water Calcium ions, sugar - water Solution Solute solvent Salt water blood salt water Calcium ions, sugar water

A salt water solution Solute (salt) Solvent (water) 8.1: A solution is a type of mixture A salt water solution Solute (salt) animation Solvent (water)

Types of Solutions Gas Solution: Liquid Solution: Solid Solution: 8.1: A solution is a type of mixture Types of Solutions Gas Solution: Ex: air = oxygen (an other gases) dissolved in nitrogen Liquid Solution: Ex: vinegar = acetic acid dissolved in water Solid Solution: Ex: bronze = tin dissolved in copper Must first be melted to a liquid, then mixed, then cooled to solid Mixed? Ex: soda = carbon dioxide dissolved in water solution Ex: saltwater = salt dissolving in water

Solution Worksheet solute solute solute solute solute solute solute solvent solvent solvent solvent solvent solvent solvent solvent

8.1: A solution is a type of mixture Suspensions Suspension: the particles added are larger than those found in a solution, so instead of dissolving, these larger particles turn the liquid cloudy Ex: Flour added to water Can sometimes separate the components of the suspension using a filter

Solvent and solute particles interact 8.1: A solution is a type of mixture Solvent and solute particles interact The parts of a solution are not changed into new substances The solute and the solvent can still be physically separated, though they do interact Ex: a solid dissolves in a liquid, the particles of the solute are surrounded by particles of the liquid (solvent) The solute particles become evenly distributed through the solvent

Solvent and solute particles interact (2) 8.1: A solution is a type of mixture Solvent and solute particles interact (2) The way a solid compound dissolves in a liquid depends on the type of bonds in the compound Ionic compounds split apart into individual ions Ex: table salt dissolves in water – the sodium and chloride ions separate, and each ion is surrounded by water molecules Covalent compounds dissolved in water, the molecules stay together and are surrounded by solvent molecules Ex: table sugar dissolves in water – C12H22O11 stays as such

Properties of solvents change in solutions Solutes change the physical properties of a solvent in every solution A solution’s physical properties differ from the physical properties of the pure solvent Dependent on the amount of solute added

Lowering the Freezing Point Freezing Point: temperature Liquid  Solid A solvent’s freezing point is lowered when a solute is dissolved in it Ex: add salt to water – freezing point drops below 32oF (0oC) Useful for snow and ice on sidewalks and roads (water freezes at a lower temperature, can help to melt ice) A limit: can get down to -6oF (-21oC) before the melted ice will freeze again Ice cream maker: Canister surrounding ingredients holds a mixture of salt and ice The lower freezing point causes the ice to melt, absorbing heat from surroundings This includes the ice cream ingredients, which get chilled Then tiny ice crystals form all at once in the ice cream mixture rather than a few crystals growing larger over time (as would happen in a regular freezer)

Raising the Boiling Point Boiling Point: temperature liquid  gas Boiling point of a solution is higher than the boiling point of the pure solvent Solution can remain a liquid at a higher temperature than its pure solvent Ex: boiling point of water = 212oF (100oC) Salt raises the boiling point of water Dependent on amount of salt added Summary: a solute lowers the freezing point and raises the boiling point of the solvent in the solution Extends the temperature range in which the solvent remains a liquid Uses: antifreeze in a car’s radiator (ethylene glycol added to water) Prevents the water from freezing in the winter Keeps it from boiling in the summer

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