Water: everything else. If it’s water, it’s hydrogen bonding, table G, or review of thermochem. Everything in this power point should be in your head.
Water is held together by polar covalent bonds, and the molecule is polar because it’s bent, it does NOT have radial symmetry. Hydrogen bonding between molecules, caused by the semi-permanent dipoles (caused by the great difference in electronegativity between oxygen and hydrogen atoms) create this magnetic “stickiness”, molecule to molecule. Because of this hydrogen bonding, water has... High boiling point considering it is so small Low vapor pressure (it does not evaporate quickly) Good surface tension Low density solid as compared to the liquid water High specific heat capacity – it’s hard to change the temperature of water Like dissolves like – polar water dissolves polar molecules and most ionic compounds Hydrated crystal compounds form, like Copper (II) sufate PENTAHYDRATE
Oil floats on water because the oil is LESS dense than the water. It doesn’t mix because water is POLAR, oil is a non polar molecule. Oil molecules have radial symmetry. Oil plunges into the water, but floats back to the surfaceas soon as the density “kicks in”. Oil doesn’t sink due to having a lowerdensity than the water.
Solutions can be saturated, unsaturated, or sometimes, supersaturated. Table G gives us the guidelines on 10 kinds of aqueous solutions of 100 mL exactly. We use table G to do simple proportional math to calculate solutions larger or smaller than 100 mL. Copper II sulfate solution
On table G, the lines represent all of the SATURATION points at any temperature. If your solution has less grams of solute than the line (under),the solution is unsaturated. You can add more solute, up to the line, to fill your solution to the maximum point. No solutions can go over the line, although table sugar, sucrose, can supersaturate water, The water needs to be heated to a boil. Stir in LOTS of sugar, which dissolves better when hot, then let the solution cool without shaking. The water is “tricked” into holding more solute of sugar than could be stirred in if the water started out cold.
Water molecules “juggle” the polar molecules, or the ions, that dissolve into it. There is a limit to the number of particles that can be held by a given volume of water. That limit is known as the saturation level. It’s based upon volume and temperature. It’s clearly outlined in table G. Too much solute into a given volume of water results in precipitates. The solid at the bottom ofthe flask will continue to dissolve into solution, at the same time more of the dissolved particles will precipitate out. Solutions at saturation with excess solute exist in a dynamic equilibrium, they do not “stop”.
Electrolytes are solutions with loose ions. Electrolytes conduct electricity, Non-electrolyte solutions DO NOT conduct electricity. Battery devices are safer in the shower! Home water has sodium fluoride, sodium chloride, And probably some other ions in it, so it will conductelectricity.
Like dissolves like. Density allows for layering of liquids when mixed together. Hexane floats on water, both float on the carbon tetrachloride. Lowest density on top, highest density on the bottom.
Colligative Properties Properties of water and solutions that are affected by dissolved components. The salt in the water makes the boiling point go up. The salt in the water makes the freezing point go down. Salt can melt the snow by lowering the freezing point. This is due to adding ions into the water, giving it extra internal attraction to over come, raising the boiling point. Or, it literally puts ions in the way of the hydrogen bonding, forcing the need for an even lower temp for the hydrogen bonding to lock molecules together into a solid. We’ll do the math for this in solutions chemistry. It’s all neatly worked out, for example, 2.3 moles of NaCl into 1.3 liters of water has what boiling point? You can know this!
Droplets at the top are nearly spheres because the hydrogen bonding inside those drops pulls inward. The surface is flat because the hydrogen bonding only attracts the water to itself, not the air. Surface tension can be broken by surfactants, water has a high specific heat capacity because the hydrogen bonding makes it hard to shake those molecules up (higher kinetic energy) so it takes lots of energy to heat water up, the density of water is one gram per milliliter OR one gram per centimeter cubed. Normally six molecules of water create a hydrogen bonded ring with a hole in the center when making ice (but some exceptions exist, like 5 or 7 or 8 molecule rings). Snowflakes are six pronged because of this fact. Ice is of lower density than liquid water, water at four degrees centigrade is the most dense water of all. Water is a very polar molecule because it does not have radial symmetry, and very polar bonds. Charlie Watts drums for the Rolling Stones,