Chapter 2 Flashcards
What is matter?
Matter is anything that takes up space and has mass
can exist as a solid, liquid, or gas
composed of elements
Main elements of living organisms: carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur
Atomic Theory
states that elements consist of atoms
Atomic symbol
name of the atom or element
subatomic elements
Neutrons - neutral charge, found in nucleus
Protons - positive charge, found in nucleus
Electrons - negative charge - found outside of nucleus moving in orbitals
Mass number
number of protons + neutrons
Atomic number
same as the number of protons
also gives numbers of electrons if an atom is electrically neutral
Isotopes
atoms of the same element that differ in the number of neutrons
same number of protons but different number of neutrons
unstable and may decay, emitting radiation
Arrangement of elements in an atom
electrons constantly moving
for atoms up to number 20, 2 electrons fill first shell and 8 electrons fill each additional shell
the outermost shell is most stable with 8 electrons - octet rule
Molecule
group of atoms bonded together
compound
molecule contained atoms of more than one element
2 types of bonds
ionic - attraction between opposite charges, when atoms transfer electrons from 1 another, ex: NACL
covalent - sharing electrons to complete outer shell,
- double covalent - 2 atoms share 4 electrons; double bonds are stronger than single bonds
Ex: CH4
Reactants
molecules that participate in reactions
Products
molecules formed by reactions
Chemical Formulas and reactions
equation is balanced if the same number of each type of atom occurs on both sides of the arrow
Ex: 6CO2 + 6H2O –> C6H12O6 + 6O2
structure of water
Polar covalent bond - atoms do not share electrons equally
Hydrogen bond is weak
Properties of water
Solvency, cohesion and adhesion, high surface tension, high heat capacity, high heat of vaporization, varying density
Solvency
Due to polarity and H-bonding, water dissolves many substances
hydrophilic - molecules attracted to water
hydrophobic - molecules not attracted to water
Cohesion and Adhesion
cohesion - ability of water molecules to cling to each other due to hydrogen bonding
adhesion - ability of water molecules to cling to other polar surfaces
allows water to be an excellent water transport system
High surface tension
water molecules cling more tightly to each other than to the air above
mainly due to hydrogen bonding
heat high capacity
many hydrogen bonds linking water molecules allow water to absorb heat without greatly changing its temperature
temperature of water rises and fall slowly
takes a great deal of energy to break H bonds for evaporation
varying density
water expands as it freezes
ice acts as an insulator
Acids and Bases
acidic solutions (<7) - acids release hydrogen ions or take up hydroxide ions
ex: lemon juice, vinegar, coffee
basic solutions (>7)- take up hydrogen ions or release hydroxide ions
ex: milk of magnesia, ammonia
Buffers and pH
chemical or combinations of chemicals that keeps pH within normal limits
resists pH change by taking up excess hydrogen ions or hydroxide ions
