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The Nature of Solutions. Looks Pure…But It Ain’t!. Solutions are not pure – they are mixtures that look the same throughout. They are known as homogeneous mixtures because they have only the one phase (appearance). Components of a Solution
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Looks Pure…But It Ain’t! • Solutions are not pure – they are mixtures that look the same throughout. They are known as homogeneous mixtures because they have only the one phase (appearance). Components of a Solution • A solution is typically composed of a solvent and a solute. • The solvent is the liquid in which the substances are dissolved and the solute is the substance that is being dissolved in the solvent. • When water is used as the solvent, we call it an aqueous solution.
Mixing It Up • Soluble – The ability of a substance to be dissolved in a second substance. Usually refers to a solid that dissolves in a liquid. • Insoluble – The inability of a substance to be dissolved in a second substance. (Again, it usually refers to a solid within a liquid.) • Miscible – The ability of two liquids to dissolve within each other. • Immiscible – The inability of two liquids to dissolve within each other.
Solids dissolved in Liquids Liquids dissolved in Liquids Gases dissolved in Liquids Gases dissolved in Gases Liquids dissolved in Solids Solids dissolved in Solid What up holmes?!?!?! Types of Solutions
No More Please…I’m Full • Solubility is the physical property of a substance describing how soluble or insoluble it is. It is the mass of a solute that will dissolve in a given mass of a solvent. The more solute that will dissolve in a given amount of solvent, the greater the solubility of that substance. • When the maximum amount of a solid or gaseous solute has been dissolved in a given volume of solvent at a given temperature, a saturated solution is obtained. If you continue to add more solute to the solution – the solute will remain undissolved.
Temperature & Solubility • Different substances are affected by temperature when it comes to how soluble they are. • Solid Solutes – For most solids, the solubility increases as the temperature increases but there are exceptions. • Think of dissolving salt in hot water over cold water. • Gas Solutes – Gases tend to become less soluble as the temperature increases. Heat makes the liquid particles move more vigorously and this allows the gas molecules in the liquid to escape. • This holds importance to lakes and rivers when companies use them to dump pollution – the increase in temperature caused by the pollution lowers the amount of dissolved oxygen and asphyxiates the fish. • Liquid Solutes – There is no trend for liquids as temperature increases or decreases. • Those crazy liquids!!! No pattern…darn them!
Why Water Melts Witches • Water dissolves many things – it is known as the “universal solvent”. • Water is polar and it pulls apart the compound because the parts of the compound being dissolved are more attracted to the charges of the water than their own components. • Ionic compounds dissolve readily in water for this reason. • Solvation is the process by which ions are attracted to and surrounded by solvent molecules. We use the term hydration if the solvent used is water.
Covalent Compounds in Water • Covalent compounds may dissolve in water or they may not – it depends on the make up of the molecule. • If the molecule has a functional group attached to it or has atoms that have a significant difference in electronegativities then the molecule will be polar and will dissolve in water. This can be seen with many of the alcohol molecules like ethanol. • When this is the case, hydrogen bonding may occur in which there is an attraction between the partially positive hydrogen of one molecule to the partially negative oxygen of a neighboring molecule. • If the molecule is composed of atoms that do not have a significant difference in electronegativities then the molecule will not dissolve in water – such is the case with gasoline.
Applications of this Stuff! Hi…I’m a fancy-looking model hired to talk to you about the usefulness of…Oh no!…My coffee!…My shirt!…My modelling!!!
Getting Zestfully Clean! • Soaps and detergents contain both polar and nonpolar parts. • The polar part (the head) of the molecule readily dissolves in water – we say it is hydrophilic. • The nonpolar part is a long hydrocarbon chain (the tail) that does not dissolve in water – it is hydrophobic. • When the soap is placed in water, micelles will form. These spherical structures allow the hydrophilic heads to dissolve within the water while allowing the hydrophobic tails to hide from it.
The micelles will quickly form when the soap is placed in water. They do not clump together as many of the heads of the soap molecules are ionic and the like charges will keep a little distance between neighbouring micelles. This ensures a solution of sorts between the water and the soap. Micelles and Soapy Water
Soaps get stains out because the hydrophobic tails hide from the awful water in the dirt and grease of the stain. Your washer agitates the water which smashes the micelles against the stain and spreads out the soap. The tails dig into the stain and the same agitation pulls against the hydrophilic head and shakes the stain loose bit by bit. The stain is gone and the dirt goes down the drain. Stain out is good! Cleaning Your Act up
