Post on 29-Dec-2015
Matter
Defined as anything that occupies space and has mass
Everything we see around us is matter Soil Air Water Rocks Plants Animals
States of Matter Kinetic Energy—energy of motion; all
particles of matter are in constant motion and therefore have kinetic energy
The temperature of matter is an indirect measurement of the particles’ average kinetic energy
At low temperatures, the particles have very little kinetic energy and move very little
At high temperatures, the particles can have enough kinetic energy to fly about at thousands of kilometers per hour
States of Matter
Solid Has a definite shape A definite volume Very difficult to compress Particles are packed close together and
held rigidly
States of Matter
Liquid Has the shape of its container Has a definite volume Difficult to compress Particles close together but free to move
States of Matter
Gas Has no definite shape Has no definite volume Relatively easy to compress Particles far apart
Plasma A hot gas in which atoms are partially
broken down to form charged particles, or ions
States of Matter
When the substance reaches a certain temperature, called the melting point, the particles have enough energy to break loose from their rigid positions and form a liquid
When a liquid is heated to the boiling point, the particles gain enough kinetic energy to break away from each other forming a gas
Classification of Matter
Substance: a form of matter with unique properties that make it different from every other substance
Examples: Water, copper, baking soda, table salt, aluminum, etc.
Elements: substances that cannot be broken down into simpler substances by ordinary chemical means
Examples: Oxygen, hydrogen, gold, iron, lead,
potassium, nitrogen, silicon (other elements listed in the periodic table of the elements)
Not all elements are found as single atoms
Molecules: groups of two or more atoms that are linked by chemical bonds to form distinct units
These two-atoms elements are called diatomic elements; other elements exist as larger molecules Examples of diatomic elements: hydrogen,
oxygen, nitrogen, flourine, chlorine, bromine, and iodine
Abundance of Elements 118 elements identified thus far 88 occur naturally in significant amounts More than 99% of the earth’s crust,
oceans, and atmosphere is made up of only eight elements
Oxygen-the most abundant element in the earth’s crust
Iron-the most abundant element in the earth as a whole
Hydrogen-the most abundant element in the universe
Compounds
A substance that can be decomposed into simpler substances
Examples: water (H2O) and table salt (NaCl),
A compound has properties quite different from those of the elements from which it is formed
Example: hydrogen-highly flammable; oxygen-flammable; H2O-commonly used to put out fires
Formula
A molecule of a compound is composed of different types of atoms linked together
The compound may be represented by a formula-a grouping of symbols that tells what types of atoms compose the compounds and the number of each type of atom in one molecule of the compound
Ex. H2O; CO; CO2; C6H12O6
Pure Substances
Elements and compounds Definite composition (relative
amounts of each element in a given compound are unchangeable, no matter where the compound may be found)
Homogeneous (same kind)-composed of the same kind of matter throughout the sample
Mixtures
A substance consisting of two or more pure substances that are physically mixed but not chemically combined
Each component retains its own properties
Each can be present in various proportions and can be separated from the mixture by physical means
Heterogeneous Mixtures
Consists of pure substances that are incompletely mixed
Each component in a heterogeneous mixture forms a distinct phase—a homogeneous part of a system that is in contact with but physically distinct from other parts of the system
Examples:
Dalton’s Atomic Theory 1. Every element consists of tiny,
indivisible, indestructible particles called atoms
2. All of the atoms of a particular element have the same size, mass, and chemical behavior
3. Differences in properties of elements result from differences in the atoms of the elements
4. The atoms of the elements combined in a compound are combined in a definite ratio
5. A chemical reaction is the result of rearrangement, combination, or separation of atoms
The Law of Definite Composition States that the ratios of the masses
of each element in a given compound are always the same
Example on pg. 22
The Law of Multiple Proportions States that when two elements can
combine to form more than one compound, the masses of one element that combine with a fixed amount of the other element are in a ratio of small whole numbers
Example on pg. 22
Section 2.2: Properties and Changes of Matter One type of matter may be
described, identified, or distinguished from another by its properties.
Physical Properties
Properties that describe a substance’s appearance
Include: color, odor, density, hardness, solubility, taste, state, boiling point, and melting point
Can be measured without changing the identity or composition of the substance
Chemical Properties
Properties that describe how matter reacts to change into other chemically different substances having different properties
That iron rusts easily in moist air and that propane burns readily are chemical properties of these substances
Can only be determined through chemical reactions, which change the identity of a substance
Physical Changes Changes in the physical appearance of
matter that do not change the identity or chemical composition of a substance
Physical changes may often be reversed by physical processes
Change of state, conversion of heterogeneous to homogeneous matter, metal hammered into a sheet, tearing a sheet of paper, crushing a large rock into gravel, cutting your hair, etc.
No change in chemical identity results, only changes in shape or size
Chemical Changes
A change in which a substance becomes a different substance with a different composition and properties
Sodium–a shiny, soft, poisonous metal that reacts violently with water
Chlorine—a greenish, poisonous gas with an irritating odor
When sodium and chlorine react chemically, a white crystalline solid with a salty taste is formed, namely sodium chloride
Chemical Changes
Other examples: Rusting of iron The digestion of food The grilling of steaks The burning of gasoline The cooking of eggs The burning of a match
Chemical Changes
Chemical changes can be reversed only by other chemical changes Not all chemical changes can be
reversed The cooking of an egg
Chemical Changes
A number of observations can be made that will suggest that a chemical change has occurred Formation of a gas Formation of a precipitate (an insoluble
substance) Liberation or absorption of heat, light, or
some other form of energy A distinct change in color
Separation of Mixtures
Distillation—used to separate homogeneous mixtures in liquid form if the components have widely differing boiling points Simple Distillation
When a mixture has components with boiling points that are close together, fractional distillation is used
Separation of Mixtures
Fractional Crystallization Used to purify a solid containing a
relatively small amount of solid impurity Chromatography
Used to separate complex mixtures Paper Chromatography Column Chromatography Gas Chromatography
Section 2.3: Subatomic Particles Subatomic Particles
Protons, neutrons, and electrons Electrons—has a negative charge Proton—has a positive charge,
located in the nucleus Neutron—has no charge, located in
the nucleus Rest of the notes in this section will
come from the videos
Section 2.4: Atomic Number, Mass Number, Isotopes, and Ions The number of protons in the nucleus
determines the identity of an element
Atomic number—the number of protons in the nucleus Denoted by the symbol Z
All atoms of the same element have the same number of protons and hence the same atomic number, Z
Mass Number
Denoted by the symbol A The sum of the number of protons
and the number of neutrons in a nucleus A = Z + N
Nuclear particles, whether protons or neutrons, are known collectively as nucleons
The mass number is not really a mass; it is a number of nucleons and must be a whole number
Ions Atoms or molecules that have a
different number of electrons than protons
An ion with more electrons than protons is called and anion Has a negative charge
An ion with fewer electrons than protons is called a cation Has a positive charge
In neutral atoms, there are equal numbers of electrons and protons
Section 2.5: Atomic Mass
An atom’s atomic mass measured in atomic mass units approximately equals the atom’s mass number Atomic mass units denoted a u
Mass Spectrometer Used to measure atomic masses with
high precision Mass Spectrum
A record of the mass distribution of particles in a sample
Average Atomic Mass
Calculated by finding the weighted average
Example: pg. 34 Track team Example 2.2 pg. 35