Unit 2 Flashcards
chemistry
the study of the composition and structure of matter and of the changes that matter undergoes
matter
Whatever occupies space and can be percieved by our senses
mass
The quantity of matter
The quantity of matter is conserved
The Law of Conversion of Mass
No mass is lost from the start of a process to the end
extensive property (of matter)
a property that depends on the amount of substance (mass, volume, etc.)
Extensive properties are a physical property of matter
intensive property of matter
a property of matter that does not depend on the amount of substance (color, melting point, density)
Intensive properties are physical properties of matter
Physical property of matter
Can be observed without doing a chemical reaction (luster, hardness, color)
Chemical property of matter
Property that can be observed through chemical reaction (flammability, reactivity, etc)
Pure Substance
- Same physical and chemical properties throughout
- Cannot be separated into simpler substances by a physical process
ex. elements, compounds
Mixture
- Combination of two or more pure substances
- Can be separated by physical processes
Element
A pure substance that cannot be separated into simpler substance by any chemical process
This includes diatomic and polyatomic molecules w only one element
Common Diatomic Molecules
Br I N Cl H O F
Common Polyatomic Molecules
P and S
Compounds
- Pure substance composed of two or more different elements bonded together in fixed proportions (ex. water, carbon dioxide)
- Compounds can be broken down into individual elements via chemical means
- All samples of a particular compound contain the same elements combined in the same proportions (The Law of Constant Composition/Law of Definite Proportions)
The chemical formula denotes the elements and their respective proportions in a given compound. If these proportions change, the compound has changed.
The Law of Constant Composition/ The Law of Definite Proportions
All samples of a particular compound contain the same elements combined in the same proportions
Homogeneous Mixtures
Components are distributed uniformly through the sample and have no visible boundaries or regions
Ex. sugar in coffee
Heterogeneous Mixtures
Components are not distributed uniformly, and there may be distinct regions with different compositions
Ex. sand in water
Plasma
A state of matter, superheated matter similar to a gas, but made up entirely of charged particles
Lavoisier 1789
- The law of multiple proportions and mass cannot be created/destroyed
- If two elements can form more than one compound together, the ratio of the masses of the second element will always be a whole number when combining with a fixed mass of the first element
Eg. CO and CO2 (same amount of carbon, whole number ratio b/w oxygen and carbon)
Dalton 1807
- Atoms are indestructible+ Atomic Theory+ Law of Multiple Proportions
Atomic Theory (Dalton 1807)
- Matter is composed of atoms, the smallest particle capable of participating in chemical reactions
- Elements contain only one type of atom, characteristic of that particular element
- Atoms of one element have different properties than atoms of other elements
- Law of definite proportions
- Atoms are neither created nor destroyed during a chemical reaction, but are rearranged
Mendeleev-1869
Arranged the elements to form the Periodic Table of Elements
Goldstein 1885
- Discovered positive particles
Thomson 1897
Discovered the electron using cathode rays, developed the plum pudding model
Rutherford 1907
- Gold foil experiment
- Alpha particles used to bombard gold foil, mass discovered at the center of the atom
- The atom itself is mostly empty space
Milikan-1909
Determined the mass and charge of an electron with the oil drop experiment
Bohr 1913
Electrons orbiting in shells around the nucleus, can be excited and move to higher energy orbitals
Heisenberg 1925
Uncertainty principle: You cannot know the energy and location of an electron at the same time
Chadwick-1932
Discovered the neutron, necessary to balance the positive nucleus
Atomic Mass Units (amu)
- unit used to express the relative masses of atoms and subatomic particles
- Carbon 12= 12 amu (6 protons + 6 neutrons)
- 1 amu =1 dalton (Da)
The Modern Periodic Table Periods
- Period 1: Alkali Metals
- Period 2: Alkaline Earth Metals
- Period 17: Halogens
- Period 18: Noble Gases
Metals Characteristics
- Shiny solids (besides Hg)
- Conduct heat and electricity
- Are malleable
Nonmetals characteristics
- Solids, liquids, and gases
- Nonconductors
- The solids are brittle
Metalloids
- shiny solids (like metals)
- brittle (like nonmetals)
- semiconductors
Aston-1919
- Aston developed a mass spectrometer, which showed through experimentation that two different masses of neon gas exist
Ions
- Neutral atoms that gain/lose electrons become ions
- Ions are held together by electrostatic force (opposites attract)
Cation vs. anion
- Cations have a positive charge (less electrons than normal)
- Anions have a negative charge (more electrons than normal)
Ionic Compounds
- Made from a metal and a nonmetal
- Metals form cations; nonmetals form anions
- Charges depend on periodic table location
formula unit
the smallest electrically neutral unit of an ionic compound
Molecular compounds
Composed of atoms held together in molecules by covalent bonds and are composed of nonmetals
Covalent bonds
Bond between two atoms created by sharing one or more pairs of electrons
Molecular formula
Shows the number and type of atoms present in one molecule of a compound
Empirical formula
Shows the smallest whole-number ratio of elements in a compound
