Chem 101 Week 1-2 Overview

Chemistry

study of matter, its properties, and how it changes

Matter

anything that has mass and occupies space

Solid

definite shape and volume

Liquid

definite volume but takes the shape of its container

Gas

no definite shape or volume

Physical property

observed without changing the substance's identity like color, density, melting point

Chemical property

describes a substance's ability to undergo a chemical change like flammability and reactivity

Physical change

changes appearance or state but not chemical identity like ice melting

Chemical change

Produce one or more new substances like rusting or burning

Element

Pure substance containing only one type of atom example hydrogen

Compound

Two or more different elements chemically bonded in a fixed ratio example water

Mixture

Two or more substances physically combined but NOT chemically bonded

Homogeneous mixture

uniform throughout aka a solution example saltwater

Heterogeneous mixture

Composition is not uniform throughout example oil with water

Pure substance

Has a fixed composition, includes elements and compounds

Atom

Smallest unit of an element that retains that element's chemical properties

What charge does a proton have?

Positive

What charge does a neutron have?

Neutral

What charge does an electron have?

Negative

Nucleus

Center of an atom containing protons and neutrons

Where do electrons occupy in a cell?

Occupy regions outside the nucleus

Where does most of the atoms mass come from?

Protons and neutrons

Atomic number

Number of protons

Do protons equal electrons in a neutral atom?

Yes

Mass number

Protons + neutrons

How to calculate the number of neutrons?

mass number - atomic number

Isotopes

Atoms of the same element, same number of protons different number of neutrons

Ion

Charged atom or molecule formed by gaining or losing electrons

Cation

Positive ion, lost electrons

Anion

Negative ion, gained electrons

How are elements arranged on the periodic table?

By increasing atomic number

Periods

Horizontal rows

Groups/families

Vertical columns, these elements often have similar chemical properties

Group 1

alkali metals

Group 2

alkaline earth metals

Group 17

Halogens

Group 18

Noble gases

Metals

Mostly found on the left side of the periodic table, usually good conductors of heat and electricity

Nonmetals

Mostly found on the right side of the periodic table

Metalloids

Have properties between metals and nonmetals

Valence electrons

Electrons in the outermost occupied energy level, they participate in chemical bonding

True or False: Atoms become more stable when their outer electron shell is filled

True

Octet rule

Many atoms tend toward having 8 valence electrons

Ionic bonding

Involves electron transfer followed by attraction between oppositely charged ions, usually happens between a metal and nonmetal

What atom loses electrons during ionic bonding?

Metal loses electrons and becomes a cation

What atom gains electrons during ionic bonding?

Nonmetals gain electrons and becomes an anion

Covalent bond

Atoms share electrons, usually occurs between nonmetals

Single bond

One pair of electrons shared

Double bond

Two pairs of electrons shared

Triple bond

Three pairs of electrons shared

Ionic bond summary

Electrons are transferred, usually a metal + nonmetal, produces ions

Covalent bond summary

Electrons are shared, usually a nonmetal + nonmetal, produces molecules

Chemical symbol

Represents an element

Subscript

Tells how many atoms of an element are present

Example: H2O, 2 hydrogen atoms, 1 oxygen

Coefficient

Tells you how many molecules/formula units are present

Example: 2H2O, 4 hydrogen atoms, 2 oxygen atoms, 6 atoms total

Reactants

Starting substances

Products

Substances formed

Law of conservation of mass

Matter is not created or destroyed during an ordinary chemical reaction, number of each type of atom must be equal on both sides

What should be done with the coefficients and subscripts when balancing equations?

Change coefficients, never change subscripts to balance an equation

Acid

Produces/increases H+ in aqueous solution, pH below 7

Base

Accepts H+ or produces OH- in common aqueous solutions, pH above 7

Neutral

pH=7 at room temperature

What does it mean when someone says the pH scale is logarithmic?

A change of 1 pH unit represents a 10-fold difference in hydrogen ion concentration

Example: pH 3 is 10x more acidic than pH 4 in terms of H+ concentration

What does meters (m) measure?

Length

What does gram (g) measure?

mass

What does liter (L) measure?

volume

Kilo (k)

1,000 or 10^3

Centi (c)

0.01 or 10^-2

Mili (m)

0.001 or 10^-3

micro (μ)

0.000001 or 10^-6

What does 1 kg equal in grams?

1,000 g

What does 1 g equal in milligrams (mg)?

1,000 mg

What does 1 liter (L) equal in milliliters (mL)?

1,000 mL

How do you find density?

mass + volume with common units of g/mL or g/cm^3