Atoms and molecules
Mater? (Better Definition)
is anything made of atoms or parts of atoms.
Non-polar covalent bonding
the resulting electron density is spread out in a fairly even manner around the molecule.
Intermolecular Attractions
These are weaker forces between molecules that happen as they pass near each other or bump into each other. They are much, much weaker than covalent and ionic bonds.
Cohesion
is the attraction of water molecules to other water molecules.(Or any type of molecule attracted to the same type.) Cohesion is caused by hydrogen bonding; since water has a lot of hydrogen bonds, it is highly cohesive.
Density
For most substances, solids are denser than liquids, but in the case of water, ice is actually less dense than liquid water. This is because water actually expands while freezing, when most substances expand as a liquid.
Atoms
are the fundamental building blocks of matter.
Polar covalent bonding
If the electron density is uneven, the molecule has regions that are more positive in character and regions that are more negative in character.
Hydrogen Bonds
Hydrogen is bonded to a very electronegative element (F, O, or N only!) which makes a very polar covalent bond. The partially + hydrogen on one molecule is attracted to the partially - atom on another molecule. This causes the highly polar molecules to stick to one another.
Surface Tension
Related to cohesion is surface tension. Because water molecules tend to stick together, the surface of water has a special resistance to being broken.
Solubility
Because of water’s hydrogen bonding, it can dissolve most other substances that are either polar or ionic, earning it the nickname universal solvent. This is because the positive hydrogens on the water molecules are attracted to the negative portions of polar covalent molecules (or negative ions) and the negative oxygen atoms are attracted to the positive parts. This means that water in cells and in the blood can carry nutrients and other molecules throughout the body.
Element
is a type of atom, classified according to the number of protons it has.
Electronegativity
strength with witch the atom pulls on its electrons.
DNA
hydrogen bonding holds the two chains together.
Adhesion
Adhesion is the attraction of water molecules to other (different) molecules.(Or any type of molecule attracted to a different type of molecule.) Adhesion is caused by hydrogen bonding and the attractions between + and - regions of polar substances.
Water travelling up the roots and stem of a plant
or along a paper towel is one example of adhesion.
compound
is a pure substance formed when 2 (or more) elements are chemically bonded together.
Non-polar
If the electrons are spread out symmetrically around the molecule.
Van der Waals Forces
These are the weakest intermolecular attractions, which work similarly to hydrogen bonding, but with molecules that are much less polar or even non-polar. If the molecules get close enough, the electrons in the two molecules will interact, creating a temporary and very small partial charge.
Van der Waals forces can have a big effect when there are enough of them!
This is what accounts for a gecko’s feet sticking to a wall.
Specific Heat Capacity
Because of water’s hydrogen bonding, it takes a lot of energy to break the molecules apart. This means that it takes a lot of energy to heat up or cool down water. (Temperature relates to how quickly the molecules are moving, and if they’re stuck together, they can’t move very well.) This means water has a very high heat capacity- the highest of all the common materials!
A Chemical Bond
holds molecules and crystals together through the sharing and transferring of electrons (very strong)
electronegativity.
Different elements have different amounts of attraction to the electrons around them. This is called
Ionic Compounds
Ionic compounds are formed between a metal and a nonmetal.
Boiling and Freezing
It also means that water is difficult to boil- you have to heat it up a lot more than other molecules to break apart the liquid into a gas, giving water a high boiling point. You also have to remove a lot more energy to freeze it, resulting in a low freezing point.