Chem Midterm Exam

measurement

finding the size or amount of something

scientific notation

a way to write big or small numbers using powers of 10

ex: 1,000 = 1 × 10³

significant figures

the digits in a number that matter

ex: 2.50 has 3 sig figs

dimensional analysis

changing units using math

ex: meters to centimeters

states of matter

• solid

• gas

• liquid

matter

anything that has mass and takes up space (trees, water, buildings)

five traditions areas of study in chemistry

1. organic chemistry

2. inorganic chemistry

3. biochemistry

4. analytical chemistry

5. physical chemistry

independent variable

variable that you change during the expirement

dependent variable

variable that is observed during expirement

solid state

a form of matter that has a definite shape and volume

liquid state

particles in liquid are free to flow , and a liquid takes shape of its container

gas state

a form of matter that takes both shape and volume of its container

vapor

used to describe a gaseous state of a substance that is generally a liquid or solid at room temp. as in water vapor

physical change

some properties during it change but the composition of the material does not change

density

how packed the matter is

qualitative observations

describing something with words

ex: the liquid is blue

quantitative observation

• describing with numbers

ex: the liquid is 200 mL

Element

a substance made up of one kind of atom

• oxygen

compound

• two or more elements joined together

• example: water (H20)

homogeneous mixture

• only one substance

• example - saltwater

heterogeneous mixture

different substances together

• salad

physical property

something you can see or measure

• ex: color or size

chemical property

• how a substance reacts

• example: rusting

chemical change

makes a new substance

• burning paper

law of conservation of mass

• mass stays the same

• ex: nothing is lost in a reaction

Dalton’s Atomic Theory

1. all elements are composed of tiny indivisible particles called atoms

2. atoms of the same element are identical

3. atoms of different elements can pjusocallu mix together and chemically combine

4. chemical reactions occur when atoms are separated from each other, joined, or rearranged in different combinations

proton

positive particle in the nucleus

ex: hydrogen has 1 proton

neutron

neutral charged particle in the nucleus

electron

negative particle that moves around the nucleus

atomic number

number of protons

ex: carbon = 6

mass number

protons + neutrons

ex: carbon -12=12

isotope

• same element, different neutrons

example: carbon -12 and carbon -14

bohr model

shows electrons in energy levels

ex: 2 electrons in the first shell

frequency

• how often a wave occurs/happens

• more waves = higher frequency

wavelength

distance between waves

• long waves = low energy

energy

ability to do work

• light energy

metals

• shiny, conduct electricity

• ex: iron

nonmetals

• dull, poor conditons

• oxygen

metalloids

have metal and nonmetal traits

• example: silicon

cation

• positive ion

• lost electrons

• positive metal

• ex: Na

anion

• negative ion

• negative nonmetal

ion

• anything with a charge

atomic radius

size of an atom

ionic radius

size of an ion

ionization energy

energy needs to remove an electron

• exL high IE = hard to remove electrons

electronegativity

how strongly an atom pulls electrons

• fluorine pulls hardest

scientific notation- when you move decimal to the left the exponent will be ______

positive

scientific notation- when you move decimal to the right, the exponent will be ____

negative

atomic radius

size of an atom

• decreases across a period

• increases down a group

ionic radius

size of an ion

• charged atom

element

pure substance only made up of one kind of atom

compound

A pure substance made of two or more different elements chemically bonded together.

cations

An ion with a positive charge because it loses electrons.
Example: Na⁺

anion

An ion with a negative charge because it gains electrons.
Example: Cl⁻

ionization energy

energy needed to remove a valence electron

electronegativity

An atom’s ability to attract electrons

Matter:

Anything that has mass and takes up space.

mass

the amount of matter in an object.

Electromagnetic Spectrum:

The range of all types of electromagnetic radiation, from radio waves to gamma rays.

Atomic Absorption Spectrum:

A pattern of dark lines showing the specific wavelengths of light an atom absorbs when electrons move to higher energy levels.

Wavelength (λ)

The distance between two waves (crest to crest).

Trend:

• Longer wavelength → lower energy

• Shorter wavelength → higher energy

• Calculation:

  λ=cfλ=fc​

Frequency (f)

Meaning:
The number of waves per second.

Trend:

• Higher frequency → higher energy

• Lower frequency → lower energy

Calculation:

f=cλf=λc​

Energy (E)

Meaning:
The amount of energy carried by a wave.

Trend:

• Higher frequency → higher energy

• Shorter wavelength → higher energy

Calculation:

E=h×fE=h×f

Constants to Know (SPEED OF LIGHT ) + PLANCK’S CONSTANT

• Speed of light:

c=3.0×108 m/sc=3.0×108m/s

• Planck’s constant:

h=6.63×10−34 J\