chapter two of exam

atom of an element

The atom is the basic unit of matter. -The smallest part of an element while still being that element. -

size of atom

Very small. -100 million atoms in a row would be \~ 1 cm.

atoms are made up of

protons, neutrons, & electrons

matter

Anything that occupies space and has mass

mass

The quantity of matter an object has

weight

Force produced by gravity acting on the mass of an object.

density

The mass of an object divided by its volume.

molecules of matter are in…

constant motion, the speed they move and the distance between molecules determines the "state" matter is in.

solid state of matter

\-Matter maintains a fixed volume and shape. -Little space between and not much movement of molecules.

liquid state of matter

Matter maintains a fixed volume but not a fixed shape. -Some space between and molecules are mobile.

gas state of matter

\-Matter will fill up the available volume of the area it occupies. -Lots of space between & movement by molecules.

element

Pure substance consisting of only one type of atom. -Over 100 elements, some natural, some man-made. -Just a couple dozen are used in the body for life.

John Dalton

a British Chemist, stated that "All atoms of a given element are identical."

THE BIG 4

oxygen-65%, carbon-18.5%, hydrogen-9.5%, nitrogen-3.3%

element name

\-Such as Hydrogen, Carbon, or Oxygen.

element symbol

Letter (or letters) of element. Carbon’s is C

atomic number

Top number on box. -Number of protons in the atom. Carbon’s is 6

atomic mass

Bottom number on box. -Number of protons and neutrons in an atom.---- round to whole number

isotope

atoms with extra neutrons found by Frederick Soddy--- they are known by their atomic mass number (isotopes of an element have the same chemical properties)

radioactive isotopes

unstable nucleus that "breaks down" at a constant rate.

radiocarbon dating

used to date specimens

radiation therapy

used to kill cancer

radioactive markers

used to “tag” molecules

ions

when an atom will gain or lose an electron and will thus have a net charge, these are known as ions

cation v. anion

c- positive /// p-negative

atoms are held together by…

chemical bonds-

the bonds that are formed from electrons are called the

valance electrons-----hydrogen and helium want 2 the rest want 8

H-O-N-C

order of the big 4 for bonds going from1-4

covalent bonds

formed when two atoms share their electrons to satisfy its valence requirements

ionic bonds

attraction between oppositely charged atoms-- will give up electron

polarity

When electrons, and thus charge, are unevenly distributed across a molecule

hydrogen bonds

Special bonds formed by charge attraction due to polarity involving hydrogen atoms on one of the compounds

van der Waals forces

like hydrogen bonds but slight charge with a bunch of atoms grouped together

cohesion

The attraction of water molecules for other water molecule due to hydrogen bonds. -It is how water beads on some surfaces and water bugs walk on water

adhesion

The attraction of water molecules for different molecules, again due to hydrogen bonds. -It is why water is measured at the bottom line in a glass container. (water clings up onto the glass)

capillarity

attraction that results in rise of water-- water clings to side of test tube

density

Water is less dense as a solid, ice, than as liquid water. -Because of this ice floats- important for life bc cold weather ice over pond keeps heat in

thermocline

when water has the biggest increase in temp

density goes down

as concentration of solute goes down

aqueous solution

where solvent is water

solutions

mixture of water and another substance where solute is completely dispersed by water

solute

compound that is dissolved

solvent

compound that dissolves the solute by hydrogen bonds

saturation poing

concentration at which no more solute will be dissolved in the solution

non ionized water molecule

H2O

hydroxide molecule

H+ and OH-

pH scale

potential of hydrogen (number of hydrogen ions) 0- extremely acidic ((high number of H+)) to 14 extremely basic (((low number of H+)))----- pure water is at 7

acid

A substance that increases the number of H+ in a solution. (Compared to OH- )

a base

A substance that decreases the number of H+ in a solution

buffers

Weak acids and bases that reacts with strong acids or bases to prevent drastic changes in pH- important for life