Pre - Chemistry week 3

protons

# of electrons = # of

Condensing

(gas to liquid)

Depositing

(gas to solid)

Vaporization or boiling

(liquid to gas)

Freezing

(liquid to solid)

Subliming

(solid to gas)

Melting

(solid to liquid)

In the lab

, formation of a precipitate, a color change, gas bubbles, or a release of heat are evidence of chemical change. Note that physical changes can give the same evidence as chemical change (for example, boiling makes gas bubbles), so it takes practice and experience to recognize the difference.

Pure substances

- made up of one substance that cannot be physically separated.

compounds

2 or more different atoms bonded together

Heterogeneous Homogeneous

2 types of mixtures

Compounds elements

2 types of pure substances are:

solid liquid gas

3 states of matter

physical property

A _________property does not change the chemical composition of a substance.Examples include color, odor, boiling point, density, conductivity, and physical state.

number and type of atoms in a molecule

A chemical formula tells the

they tend to become positively charged in compounds.

A chemical property of metals

they tend to become negatively charged in compounds.

A chemical property of nonmetals is

nonmetal atoms

A molecule is made up of two or more

isotopes

Atoms of the same element that have different numbers of neutrons

CHANGES IN PHYSICAL STATE OF MATTER

CHANGES IN PHYSICAL STATE OF MATTER

Periodic Table of the Elements

Chemists organize matter on

condensing, then freezing (or depositing

Decreasing the temperature of a gas causes

name and symbol

Elements on the periodic table have a name and a symbol. The symbol is from 1 to 3 letters long where the first letter is capitalized and the remaining letters are lowercase.

law of multiple proportions

If two elements combine to form different compounds, the ratio of masses of the second element that react with a fixed mass of the first element will be a simple, whole-number ratio

melting, then vaporization or subliming

Increasing the temperature of a solid causes

gas

Matter is far apart and uniformly distributed in container Indefinite shape that assumes shape of container Compressible Indefinite volume Most energy

Liqued

Matter loosely packed and moves past itself Indefinite shape that assumes shape of container Incompressible Definite volume Intermediate energy

Solid

Matter tightly packed Definite shape In-compressible Definite volume Least energy

parts of periodic table

Metals appear to the left of the metalloids and include aluminum (Al) Nonmetals appear to the right of the metalloids

Facts about elements:

Of the more than 100 elements, 81 are stable. About 10 elements account for 95% of the mass of the Earth's crust Oxygen accounts for about 50% of the mass of the Earth's crust and about 65% of the mass of the human body

formulas

Some chemical formulas use parenthesis to indicate more than one of a particular unit. For instance, the formula for antifreeze is C2H4(OH)2, which consists of 2 OH units. The atom count is 2 carbon atoms, 6 hydrogen atoms, and 2 oxygen atoms (a total of 10 atoms).

increasing temperature

Substances change state with

compounds always contain the same proportions of elements by mass. For example, sodium chloride is always 39.3% sodium and 60.7% chlorine by mass

The Law of Definite Composition states

chemical formula

The chemical formula can be written from a description of the composition. example, the molecule niacin consists of 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and 1 oxygen atom. The chemical formula is C6H6N2O. As before, subscripts indicate the number of atoms in the formula (when only one atom of a given type is present, no '1' is written).

atomic number

The periodic table is arranged by

atomic mass

The total mass of the protons, neutrons, and electrons in a single atom when it is at rest.

mixtures pure substances

Two classifications of matter

Homogeneous

Type of mixture - the same throughout, like salt dissolved in water (paint, solutions)

Ants Have No Fear Of Ice Cold Beer

acronym for diatomic elements Hydrogen (H2 Nitrogen (N2 Fluorine (F2) Oxygen (O2) Iodine (I2) Chlorine (Cl2) Bromine (Br2)

Metalloids

appear with an edge of their box on the stepped line of the periodic table and include B, Si, Ge, As, Sb, Te, Po, and At. Note that Al also appears on the stepped line but Al is an exception. Al is a metal.

Compounds

can be chemically separated into elements

mixtures

can be physically separated into pure substances

Elements All known elements appear on the Periodic Table of the Elements

can not be broken down by chemical reactions.

Chemical properties

describe the chemical reactions that a substance could undergo (or not undergo), meaning that the composition of elements changes.

compounds always contain the same proportions of elements by mass

gaseous elements have symbols with an italic font, liquid elements have symbols with an outline font, and solids have symbols with a Times-Roman font.

Matter

has mass and occupies space

Metalloids

have physical and chemical properties in between metals and nonmetals.

covalent bond

is a chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as

Chemical Change

means that a chemical reaction occurred. -A chemical property means that the reaction could occur, -whereas a __________ means it did occur.

Physical Change

means to change the physical state or shape of a substance without changing its chemical composition

diatomic elements

molecules composed of only two atoms, of either the same or different chemical elements -covalent

electrons

negative almost to small to measure occupy enormous volume

neutrons

nuetral add with protons for total mass

high density, high luster, high melting point, good conductors of heat and electricity, malleable (can be hammered into sheets), and ductile (can be drawn into wires).

physical properties of metals include

low density, dull, low melting point, poor conductors of heat and electricity, not malleable, not ductile, and 11 nonmetals occur in the gaseous state.

physical properties of nonmetals include

protons

positive identified by atomic number

elements

represented by chemical symbols mostly solids at room temperature mostly metallic arranged by increasing atomic number

law of definite composition

samples of a pure compound always contain the same elements in the same mass proportion.

atom

smallest representation of an element

Heterogeneous

type of mixtures - different throughout, like sand and water (salad)