Chem H Midterm Review

Independent variable

The one you change during an experiment.

Dependent variable

Changes as a result of changing the independent variable.

Graduated Cylinder

Used to precisely measure the volume of liquids, or run experiments.

Hot Plate

Used to heat substances.

Digital Balance

Used to accurately measure mass.

Physical change

Changes the appearance of a substance, without changing its chemical composition.

Examples of physical changes

Cutting/ripping a piece of paper, molding clay, crushing an aluminum can. (Color, density, melting/boiling point).

Chemical change

Identities of substances change and new substances are formed.

Examples of chemical changes

Iron rusting, wood burning, food spoiling, chemical reactions. (Burning, rotting, reacting, tarnishing, rusting, color change).

Element

A substance that only contains atoms from one type.

Compounds

Atoms of two or more different elements chemically combined.

Mixture

The addition of two or mor elements and /or compounds that are not chemically combined.

Homogeneous mixtures

Proportion of ingredients remain consistent. Juice, soda, coffee.

Heterogenous mixtures.

Not uniform throughout. Chex mix, mixed nuts, a salad.

Density formula

Mass/volume

Float

Objects will float if their density is less than 1.

Sink

Objects will sink if their density is greater than 1.

When finding volume

mass/density

When finding mass

density x volume

Democritus

Greek philosopher who developed the first ideas about atoms.

John Dalton

Believed all matter was composed of tiny particles called atoms. Created Billiard Ball Model, where he thought that atoms looked like spheres.

JJ Thompson

Used a Cathode Ray Tube to see that matter contained negative charged particles called electrons. Created Plum Pudding Model, where negative electrons spread throughout positive matter. Lots of empty spaces between negative particles.

Ernest Rutherford

Created the Gold foil experiment, where he sent fast moving radioactive alpha particles through thin pieces of gold foil. Showed that alpha particles had large deflections.

Mass number

The total mass of the nucleus. Add protons and neutrons.

When having to find neutrons or protons

mass number- protons= neutrons

Mass number- neutrons= protons

Cation ions (+)

Have more protons than electrons.

Anions (-)

Have more electrons than protons.

Calculating Atomic mass

mass of isotope 1 x percent/100 + mass isotope 2 x percent/100

Alpha Decay

Radioactive Helium-4 nuclei. 4/2 He

Beta particle

A fast moving electron with a negative charge. 0/-1 e

Gamma Ray

A high energy radioactive wave that is given off by a radio isotope. 0/0 y

Crest

Top wavelength

Trough

bottom of wavelength

Amplitude

height

Speed of light

C= 3.00 × 10^8

Speed of light formula

C= wavelength in meters x frequency in 1/s

Planks constant

H= 6.626 × 10^-34

Energy formula

E= planks constant in joules x frequency in 1/s

Aufbau Principle

States that the electrons will occupy lower energy levels first before filling in higher energy levels.

Pauli Exclusion Principle

States that a maximum of 2 electrons can occupy a single atomic orbital.

Hund’s Rule

States that electrons with the same spin must occupy empty orbitals first before occupying the same orbital.

Nuclear charge

The force of the nucleus is based on the number of protons. As protons increases, nuclear charge increases (even if electrons also increase). Affects trends Left → Right

Electron shielding

Core electron repulsions block the attractive forces between the protons and the valence electrons. Shielding increases down the periodic table Affects trends Top to Bottom

Ionization Energy

Increase going right. Decrease going down.

Atomic radius

Decrease while going right. Increase going down.

Electronegativity

Increases going right. Decreases going down.

Prefixes for binary covalent compounds

1= Mono

2= Di

3= Tri

4= Tetra

5= Penta

6= Hexa

7= Hepta

8= Octavia

9= Nona

10= Deca