Notes of a Stressed Student

Many of the properties of water link back to its structure and bonding.  The oxygen atom is covalently bonded to two hydrogen atoms, and has two non-bonding electron pairs. The oxygen has a higher electronegativity than the hydrogen, so these bonds are polar. This means that the oxygen has a partial negative charge, as the electrons are more strongly attracted to it, and the two hydrogen atoms will have a partial positive charge, as the electrons are drawn away from them. Water molecules are able to form hydrogen intermolecular bonds .  Group 16 Hydrides: Water is one of the Group 16 Hydrides (as oxygen is a group 16 element, and it is bonded to hydrogen, H 2 O) However, water defies many trends found in this group. Generally, the melt/boil point of these compounds increase going down the group, due to increased dispersion forces. Despite being the smallest hydride, it has high melting and boiling points. Properties of Water include: Relatively high melting/b...

Physical Changes: a change of state and do not create a new substance. Ice melting to water, to dry ice subliming to produce fog are physical changes. Chemical changes: a reaction where one or more substances is transformed into one or more new products. They are can be identified by observing: * A substance 'disapears' * A gas is given off (effervescence) * A solid is precipitated * A colour change occurs * A new odour is released * Light is given off Chemical Equations - used to represent a chemical reaction, showing reactants and products and their physical states. Catalysts and other agents can also be shown above the arrow between sides. Reactants ----> Products To Write a Chemical Equation: A General Guide 1. Write out reactants on the left and products on the right, often obtained from information given in a question, including states. 2. Change the little numbers at the bottom to balance the charges of each compound 3. Balance equation...

I really struggled to understand this topic, so I have put together this handy guide to the Mole, of what I would have found helpful as I tried to figure out what all of this meant. Atoms are really small, so we cannot measure them using cm or even mm, grams or milligrams. Nothing we would use in everyday life would be practical to measure their mass or length.  A mass spectrometer is used to split elements into isotopes of different masses.  The term mole (mol) represents a number, in the same way the word dozen does. However, dozen means twelve, and mole mean s 6.02 x  10 23  This is known as Avogadro's Number, and is equal to the number of atoms in 12 grams of Carbon-12. Mole is not mass, so one mole of different substances will each have different masses, but the same number of particles (6.02 * 10 23 ) That's really all the theory needed for the Mole, however, you will be asked most likely to do a number of calculations using ...