Introduction to Chemistry: Key Concepts and Principles

Serendipitous Chemistry

The unintentional discovery of a product invention or a scientific discovery.

Example of Serendipitous Chemistry

Sticky Notes, Artificial Sweetener, Vulcanized Rubber

Analyze, Calculate, Evaluate Method

A method for solving problems in chemistry.

Analyze

Make a plan, select an equation, determine knowns/unknowns.

Calculate

Rearranging equation before solving, convert measure from one unit to another.

Evaluate

Check if the answer makes sense, if data was copied correctly, if the proper equation was used, and check units.

Percentage Problems

Solved using (part/whole) x 100.

Beaker

Beaker

Beaker Tongs

Beaker Tongs

Lab Safety Guidelines

Always read the entire procedure and ask for clarification if in doubt.

Emergency Safety Equipment

Know the location and how to work emergency safety equipment.

Chemical Exposure

If a chemical gets in your eye, wash with a continuous stream of lukewarm water for at least 15 minutes.

Matter

Examples include wood, computer, soccer ball, and water bottle.

Non-Matter

Examples include light, sound, heat, and vacuum.

Mass

The measure of the amount of matter an object contains (exp units Kg, g).

Volume

The measure of the space occupied by an object (exp units l, ml, cc).

Physical Property

Is a quality or condition of a substance that can be observed or measured without changing the identity of the substance composition.

Density

A physical property that measures mass per unit volume.

Color

A physical property that describes the visual perception of light.

Shape/Size

A physical property that describes the external form or dimensions of an object.

Texture

A physical property that describes the feel or appearance of a surface.

Appearance

A physical property that describes how something looks.

Odor

A physical property that describes the smell of a substance.

Volume

A physical property that measures the amount of space a substance occupies.

State of Matter

The distinct forms that different phases of matter take on.

Solid

A form of matter that has a definite shape and volume.

Liquid

A form of matter that has an indefinite shape, flows and yet has a fixed volume.

Gas

A form of matter that has an indefinite shape and volume.

Physical Change

Some properties of a material change, but the composition of the material does not change.

Heterogeneous Mixture

A mixture that is not uniform in composition; components are not evenly distributed throughout the mixture.

Homogeneous Mixture

A mixture that is uniform in composition; components are not easily distinguished.

Element

The simplest form of matter that has a unique set of properties.

Compound

A substance that contains two or more elements that are chemically combined.

Diatomic Elements

Elements that naturally exist as molecules consisting of two atoms.

Chemical Change

A change that results in a substance with a different composition.

Pure Substance

Matter that has a uniform and definite composition.

Mixture

A physical blend of two or more substances that are not chemically combined.

Group (Periodic Table)

A column in the periodic table.

Period (Periodic Table)

A row in the periodic table.

Chemical Property

The ability of a substance to undergo a chemical change.

Reactant

A substance present at the start of a reaction.

Product

A substance produced during a reaction.

Law of Conservation of Mass

Mass is neither created nor destroyed.

Percent Error

|Experimental Value - Accepted Value| / Accepted Value x 100

Exact Numbers

Numbers that have infinite significant figures, such as count values and conversion factors.

Measured Numbers

Numbers obtained using a measuring device, limited by the number of markings on the device.

Significant Figures

Indicate the quality of the measuring device; more sig figs imply a higher quality device.

Captive Zeros

Zeros that are in between non-zero digits.

Trailing Zeros

Zeros that come after the last non-zero digit.

Leading Zeros

Zeros that precede all non-zero digits.

Multiplication with Significant Figures

The final answer should have the same number of sig figs as the measurement with the least sig figs.

Division with Significant Figures

The final answer should have the same number of sig figs as the measurement with the least sig figs.

Scientific Notation Format

A x 10^n where 1 ≤ A < 10.

Converting Scientific Notation to Standard Notation

Multiply A by 10 raised to the power of n.

Significant Figures in Scientific Notation

Only significant numbers can appear before 'x 10' in scientific notation.

Accuracy

How close measurements are to the accepted or correct value.

Precision

How close measurements are to each other.

SI Units

The first 5 SI units include length, mass, time, electric current, and temperature.

Milli-

Prefix meaning one thousandth (1/1000) of a base unit.

Centi-

Prefix meaning one hundredth (1/100) of a base unit.

Kilo-

Prefix meaning one thousand (1000) times a base unit.

Density

A physical property that describes how much mass is contained in a given volume.

Relationship of 1 ml to cm³

1 ml is equal to 1 cm³.

Density

a measure of how tightly packed an matter is in an substance (relationship between the mass of the substance and how much space it takes up (volume)

High Density

more tightly packed and has a lot of mass relative to its volume.

Low Density

less tightly packed and has less mass relative to its volume.

Density Formula

d = m/v

Density of Water

1 g/mL

Sinking and Floating

If an object is more dense than water it will sink (when placed in water), and if the object is less dense than water it will float.

FLM

Use FLM to set up problems that convert from one unit to another and give answers in correct sig figs. Consider exact and measured numbers.

Protons

Positive charge (+ 1), located in the nucleus, relatively large mass compared to electrons. (2000) (1amu)

Neutrons

Neutral charge (0), located in the nucleus, similar in size to protons. (2000) (1amu)

Electrons

Negative charge (- 1), located in the electron cloud surrounding the nucleus, very small mass compared to protons and neutrons. (1) (0amu)

Atomic Structure

Protons and neutrons are in the dense central core of the atom (nucleus). Electrons are in the electron cloud, arranged in energy levels and orbitals.

Dalton's Atomic Theory

Atoms are indivisible - Atoms cannot be divided, created, or destroyed. Not true today; we know atoms have smaller parts (protons, neutrons, electrons).

Isotopes

atoms of the same element with different # of neutrons

Atomic Number

# of protons in an element

Mass Number

total # of protons and neutrons in a nucleus

Carbon-14

Example: Carbon-14 (format is Element Name - Mass Number (Neutrons + Atomic mass(protons)

Average Atomic Mass

The weighted average of all isotopes of an element. Found on the periodic table (decimal value).

Weighted Averages

Weighted averages account for both the abundance and mass of each isotope.

Ground State

Electrons are in the lowest possible energy levels.

Excited State

Electrons absorb energy and move to higher energy levels (temporarily).

Energy Level

The main 'shell' where electrons are found.

Sublevel

Regions within energy levels (s, p, d, f).

Orbital

Specific areas where electrons are likely to be found.

s orbital

Spherical.

p orbital

Dumbbell-shaped.

Spin

Electrons in the same orbital must have opposite spins.

1st Energy Level

2 electrons, Sub Level s.