Water

Covalent bonds have two types

o   Non polar = equal sharing

o   Polar = unequal sharing

Non polar

o   If bond is between identical atoms, sharing is equal

o   Both have equal pull on the bonding electrons

Polar covalent bond

o   If bond is between two different atoms, sharing is not equal

o   Stronger bonds because of partical charges => + and – are attracted to each other

• Measure of the attraction of an atom for an electron in a chemical bond

• Some atoms attract electrons more strongly than others

• Difference is higher positive charge on nucleus

Trends

• Highest electronegativity at Fluor

• Atoms decrease in size as you go across a row because higher positive charge on nucleus pulls electrons closer => electrons are added to same. Shell as we go across a row => + and – are getting closer together

Smaller atomic size signals that electrons are pulled in tighter to the nucleus!

• Atoms increase in size as you go down a column because electrons are further from the nucleus as shells are added => + and – are getting far away

• Type of intermolecular force

• Not as strong as covalent bonds (intramolecular)

• Occurs in any molecules with OH, FH, NH

• Interactions happen because of partial charges: The oxygen is negatively charged and H positively => it can interact with another H, which is positively charged

• High heat capacity

o   Heat required to rase the temperature of the material by 1°

o   Added heat will first break hydrogen bonds instead of increasing the temp. of water. Raising the temperature to near boiling point requires a lot of heat energy per mass of water => high boiling point

• Good solvent

o   Substances that can form hydrogen bonds to water molecules will be able to dissolve

o   Ethanol can H-bond to 3 water molecules

o   Water can H-bond to 4 molecules

• Ice floats on water

o   Because of hydrogen bonds when water freezes, there are open structures full of holes in the ice = less dense than liquid water, which is fluid and can therefore have a higher density

1. Solvent molecules must separate and make room for the solute molecules

2. solute particles must separate from each other

3. the attraction between solvent and solute particles will allow them to move closer together and stay there

o   Cohesion: attraction of water molecules towards each other (H-bonds)

o   Adhesion: attraction between other substances/surfaces (H-bonds)

o   Surface tension: molecules at surface are attracted to molecules underneath, leading to a skin-like surface

homogenous mixture, one or substances dissolved in another substance

substance that dissolves

the substance in which others are dissolved (substance in higher proportions)

• a solution in which water is the solvent

• Water = universal solvent

• Mass/ volume or mol/ volume

• Ionic bonds are the strong electrostatic attraction between positive and negative ions (charged particles)

o   Cations = positive

o   Anions = negative

• Compounds composed of metals and nonmetals will be ionic

• Cations keep its element name

• Anion gets “ide”

• No prefixes are used to give number of atoms! => only 1 possible formula

o   MgO = magnesium oxide

o   NaBr = sodium bromide

• Polyatomic ions

o   Covalently bonded molecules can gain/ lose electrons, making them charged ions

§  NaSO4 = sodium sulfate

• Stages of a linear food chain:

Lowest level: Producers = green plants

2nd level: second-level organisms (herbivores, or plant eaters)

3rd level: carnivores/ meat eater => eat herbivores

4th level: second carnivores = eat the primary carnivores

• If the first level eats harmful substances, they accumulate in the higher animals/ organisms of the food chain. The higher organism eat a lot of the animals in lower levels, which meants that there is a higher ratio of harmful substances in their body.

• Therefore the biomagnification = accumulation of pollutants from the environment in living organisms via food, can be deadly: DDT disrupted the calcium metabolism in avians resulting in thin egg shells with few birds hatching => animals died. Nearly brought ospereys and other fish-eating birds to extinction

ð  Substances that will dissociate in solution are called electrolytes

ð  All ionic compounds have at least a very small solubility in water

• soap is a molecule out of a long hydrocarbon chain and a water attracting end (short ionic part)

  • hydrophobic tail and hydrophil head

• Makes it possible for oily substances to dissolve in water through forming micelles: hydrophobic tails are getting closer to each other and are building the inner core, while the hydrophilic heads stick to the water side

making soap

• Triglycerides (fats/ oils) + base (sodium hydroxide) + heat + water

• Phosphate-based molecules (PO4 3-) created the best detergents but also fertilized algea blooms that pollute waterways and choke out other green vegetation (eutrophication)

• Municipal water treatment facility

o   Using sand filters, and oxidations-substances like chlorinate-ion or fluoride-ione or UV/ O3

• Making freshwater from saltwater

o   Desalination (process that removes ions from salt water)

o   Distillation (separation through heating; using black backgrounds to absorb more heat (energy))

• Reverse osmosis

o   Use pressure to force the movement of water through a semipermeable membrane from a solution that is more concentrated to solution that is less concentrated

o   life straw: removes bacteria, viruses, parasites from water to use for drinking