Chem 1 2 3

Scientific Method

A way of learning that emphasizes observation and experimentation

Hypothesis

An educated guess that ties your observations with your background research

Law/Theory

a hypothesis turns into a law/theory when the data has backed it up multiple times

Experiment must include

• Control Variables

• Independent Variable

• Dependent Variable

Law

• summarizes what happens by

combining all past observations.

• does not provide an explanation

Theory

tested explanation of the results

• can be used to predict future

observations

Observations

background information

• Research

• well documented notes about physical and chemical changes

Scientific Notation

is a way to write numbers that are cumbersome more compactly

Exact Numbers

have an unlimited number of significant figures

Measurement

A number with a unit (for volume, mass, length, etc)

Mass

A measure of the quantity of matter within an object

Weight

A measure of the gravitational pull on the matter

Weight = mass x gravity

Lengths

1 inch = 2.54 cm

1 foot = 12 inches

1 yard = 3 foot

1 yard = 36 inch

1 mile = 5280 foot

Mass

1 pound = 453.59 g

1 pound = 16 ounces

Volume

1 cm3 = 1 mL

1 gallon = 3.7854 L

1 quart = 2 pint

1 gallon = 4 quart

Temperature

TF = TC (9/5) + 32

TK = TC + 273.15

Density

• the degree of compactness of a substance.

• characterized by volume and mass

Density = mass/volume

Matter

Anything that occupies space and has mass

• Can appear to be smooth and continuous or rough and grainy

• Composed of atoms

• Classified into 3 phases

(1) Solid

(2) Liquid

(3) Gas

Atom

Submicroscopic particles that are the

fundamental building blocks of matter.

• Most atoms are chemically reactive.

• Electrostatic forces form chemical bonds between atoms to make molecules or ionic solids.

• Molecules and ionic solids are more common than pure elements (just atoms) in nature

Solid

Anything that you can touch with a defined shape and texture. Also not mobile

Liquid

fluid that can flow from one container to another

Gas

Can expand to fill up a container and can assume the shape of a container. It can move around and be compressible and expandable

Pure substances

Composed of only one type of atom or molecule

• Can be either elements or

compounds

• Less common than mixtures

Elements

A substance that cannot be broken down into simpler substances.

• A list of the elements can be found

on the Periodic Table.

Compounds

A substance composed of two or

more elements in fixed definite

proportions.

• More common than elements

Homogeneous

Cannot identify the difference between a mixture of two components (tea with sugar)

Also called a solution

• The compositions are the same

throughout

• Uniform compositions due to

uniform mixtures of atoms or

molecules

Heterogeneous

identifiable between two layers or mixtures (pizza)

Composition varies from one region

to another

• Not uniform throughout

Mixtures

Several substances with proportions

that vary

• Can classify mixtures into how

uniformly the substances within

them mix

• Can be separated

Properties

Characteristics that distinguish one substance

from another

Physical Properties

Characteristics that can be directly observed.

• Characteristics that a substance displays without changing its composition.

• Examples: odors, boiling/melting points, density, gas, liquid and solid

Chemical Properties

The ability of a substance to form new

substances.

• Characteristics that a substance displays

only through changing its composition.

• Examples: flammability, susceptibility to

rusting, corrosiveness, acidity, and toxicity

Physical Change

Matter changes in appearance but NOT in

composition.

• Results in a different form of the same

substance.

• Examples: boiling, melting , condensation,

and changing from gas to liquid to solid.

Chemical Change

Matter does change its composition

• Characteristics that a substance displays

only through changing its composition.

• Results in a new substance.

• Examples: burning, rusting, corrosion, acidic

reactions, and explosions

Law of Conservation of Mass

There is no new matter:

• “Matter is neither created nor destroyed

in a chemical reaction”

• Applies for both chemical and physical

changes

Energy

The capacity to do work

• Able to move an object

• Many form of energy

• SI Unit of energy is Joule (J) = kgm2s-2

• calorie (cal) – the amount of energy

required to raise the temperature of 1 g of

water by 1oC

• Calories (Cal) = 1000 cal

Work

The result of a force acting on a distance

• Pushing a book across the room

Kinetic energy

associated with the motion of matter

Potential energy

associated with the position or composition of matter

Electrical energy

associate with the flow of electric charges

Thermal energy

associate with the random motions of atoms and

molecules in matter – hot objects has

more thermal energy than cold objects.

Light energy

the radiation of energy of electromagnetic waves in the visible

portion of the electromagnetic spectrum.

Chemical energy

released during a chemical reaction

Law of Conservation of Energy

“Energy is neither created nor destroyed in a chemical reaction”

• It can be converted from one form to another

• Applies for both chemical and physical changes

Exothermic

Feel hot to the touch

Reaction releases heat to the environment

Endothermic

Feel cold to touch

Reaction taking heat from the environment