8.1: A solution is a type of mixture 8.2: The amount of solute that dissolves can vary

1. Unit: Chemical InteractionsChapter 8: SolutionsWhen 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

2. 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? C Na Cl O O animation

3. 8.1: A solution is a type of mixture 8.1 A solution is a type of mixture

4. 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

5. 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

6. 8.1: A solution is a type of mixture A salt water solution Solute (salt) animation Solvent (water)

7. 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

8. Solution Worksheet solute solute solute solute solute solute solute solute solvent solvent solvent solvent solvent solvent solvent solvent

9. 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

10. 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

11. 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

12. 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

13. 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)

14. 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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