daily taks connection: water as the universal solvent ipc(9): the student knows how solution...

Daily TAKS Connection:Water as the Universal Solvent

IPC(9): The student knows how solution chemistry is a part of everyday life. The student is expected to:

(A) relate the structure of water to its function [as the universal solvent].

Solutions

Remember the following types of mixtures suspension – a mixture that looks uniform when stirred

or shaken that separates into different layers when no longer agitated

colloid – a mixture of very tiny particles of pure substances that are dispersed in another substance but do not settle out of that substance

emulsion – any mixture of immiscible liquids in which liquids are spread throughout one another

solution – a homogeneous mixture of two or more substances uniformly spread through a single phase

Solutions

Today, we’re going to focus on solutions. There are two important components of a solution: solute – the substance that dissolves solvent – the substance that does the

dissolving

Solutions

The rate that a solute is dissolved by a solvent depends on several factors:

temperature – the hotter a solvent is, the faster a solute can dissolve

shaking or stirring – the solute can be dissolved faster if more of its particles are moving and come into contact with the solvent

surface area of the solute – a solute with larger surface area dissolves faster than one with a smaller surface area – crushing or breaking a large lump of solute will increase its surface area, making it dissolve faster

Solutions

Not every substance can be dissolved into a given solvent . . . and not every solvent can dissolve every substance.

when a substance cannot be dissolved into a given solvent, it is said to be insoluble in that solvent

when a substance can be dissolved into a given solvent, it is said to be soluble in that solvent

Solutions

Water – “the universal solvent” – the majority of substances can be dissolved in water. Water has one very special property that make it good at dissolving other substances – it is polar – that is it has a partially positively charged end (the Hydrogen end) and a partially negatively charged end (the Oxygen end). Because it is polar, it can dissolve other polar substances (like alcohols and sugars) as well as ionic compounds (like salts and acids). It cannot dissolve nonpolar substances (like gasoline or oils)

Question

Which factor makes water an effective solvent?

a. The presence of molecular oxygen

b. Its lack of covalent bonds

c. The polar nature of its molecules

d. Its abundance on Earth’s surface

Question

The structure of pure water makes it a good —

a.solvent

b.catalyst

c. conductor

d.nutrient

Question

The diagram above shows water molecules and ions from an NaCl crystal. What is the most likely reason that each water molecule is arranged so that the oxygen part of the molecule faces a sodium ion?

a. The oxygen in a water molecule contains a partial negative charge. b. Gravity rotates the oxygen atoms to face the more-massive sodium ions.

c. Hydrogen atoms create repulsive forces with chloride ions. d. Oxygen atoms form covalent bonds with sodium ions.

Properties of Water that Never Change

Water always contains two hydrogen atoms bonded to one oxygen atom

2:1 ratio Formula: H20

Water expands when frozen Becomes less dense

Ice floats!! Very important to aquatic life!!

Question

Fish survive through severe winters because of the property of water that allows water to —

a. form chemical bonds as it freezes, raising the water temperature below the ice

b. increase in density while it freezes, dissolving more oxygen from the air

c. expand when it freezes, creating a floating and insulating layer of ice

d. precipitate vital nutrients when it freezes, increasing the food supply

daily taks connection: water as the universal solvent ipc(9): the student knows how solution...

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