Chapter 1 Vocab - Chem 115

Scientific Theory

A concise extensively tested explanation of widely observed nature phenomena.

Scientific Law

A concise, generally applicable statement of a fundamental scientific principle. (ex. how it happens)

Atoms

Smallest particle of an element that cannot be chemically or mechanically divided into smaller particles.

Element

Pure substance that cannot be separated into simpler substances.

Compound

Pure substance composed of two or more elements that are chemically bonded in a fixed proportion. (ex. water)

Law of Constant Composition

A compound always has the same elemental composition by mass no matter its source. (ex. pure water is always 11.2% hydrogen and 88.8% oxygen by mass)

Law o Multiple Proporations

When two masses of 1 element react with a given mass of another element to form 2 compounds, the 2 masses of the first element have a ratio of 2 small whole #’s.

Chemical Formulas

Notation that uses the symbol of the elements to represent the elemental composition of a pure substance. (ex. h20, c6h12o6, s03, s02)

Matter

Anything that has mass and operates space.

Pure Substance

Matter that has a constant composition cannot be broken down into simpler matter by any physical process. (ex. h20, Ti)

Physical Process

Transformation of a sample of matter, such as a change in its physical state, that does not alter the chemical identity of any substance in the sample. (ex. solid —> liquid, breaking a gold bar)

Intensive Property

Independent of the amount of substance. (ex. density)

Extensive Property

Varies with the amount of substance (ex. mass)

Physical Property

Can be observed without changing the substance into another substance.

Density

Ratio of mass of an object to its volume. (d=m/v)

Chemical Property

Substance that can be observed only by reacting a substance with something else.

Chemical Bond

Force that holds 2 atoms or ions in a molecule or compound together.

Molecule

Collection of chemically bonded atoms, usually neutral.

Ion

Particle consisting of 1 or more atoms that has +/- charge. (If a atom or molecule has a charge it is a ion)

Mixtures

Composed of 2 or more pure substances and are classified as either homo or hetero.

Homogeneous Mixture (Solution)

Mixture in which compounds are distributed uniformly and are the composition and appearance are uniform. (ex. coffee, salt water, orange juice (w/out pulp))

Heterogeneous Mixture

Mixture in which the components are not distributed uniformly, mixture contains regions of different compositions.

Distillation

Process using evaporation and condensation to separate a mixture of substance with different volatilities. (boiling points)

Filtration

Separating solid particles from a liquid to gas. (Ex. brita, coffee filter)

Chromatography

Process separating a mixture of substance according to their different affinities. (Ex. color strip from art classes)

Solid

Definite volume and shape.

Liquid

Definite volume but not definite shape.

Gas

Neither definite shape nor volume.

Energy

Capacity to do work (w).

Work

Exertion of a force (F) through a distance (d). w=F*d

Potential Energy

Energy stored in objects because of its position or composition.

Kinetic Energy

Energy of an object in motion because of its mass (m) and speed (u). KE= 1/2mu²

Heat

Transfer of energy between objects that occurs because of a different in their temperature.

Law of Conservation of Energy

Energy cannot be created or destroyed, but can be changed from 1 form to another.

Molecular Formula

Chemical formula that indicates how many atoms of each element are in 1 molecule of a pure substance. (ex. h20, c3h6o)

Structural Formula

Representation of a molecule that uses short lines between the symbols of elements to show chemical bonds and their atoms.

Ionic Compound

Compound that consists of a characteristic ratio of positive ions and negative ions. (ex. NaCl, CaCl2)

Empirical Formula

Chemical formula in which the subscripts represent the simplest whole # ratio of the atoms or ions in a compound. (ionic compounds are always empirical formulas.) (ex. c6h12o6 —→ ch2o)

SI Units

Set of base and derived units used worldwide to express distance and qualities of matter and energy.

Giga

10^9

Mega

10^6

Kilo

1000

Hecto

100

Deka

10

Deci

0.1

Centi

0.01

Milli

0.001

Mirco

10^-6

Nano

10^-9

Electric Current

Ampere (A)

Quantity of a Substance

Mole (mol)

Exact #’s

Determined by counting or are part of a definition.

Inexact #’s

Measured quantities and the #’s derived from them.

Precision

The extent to which repeated measurements of the same variable agree. (All in one spot on the target, not in the center though)

Accuracy

Agreement between an experimentally measured value and the true value. (Dots not close together, but are in the center of the target)

Significant Figures (sig figs)

All the certain digits in a measured value plus 1 estimated digit, the greater the # of significant figures, the greater the certainty with which the value is known.

Conversion Factor

A fraction in which the numerator is equivalent to the denominator but is expressed by different units, making the fraction equivalent to 1.

Mean

An average calculated by summing all the values in a series and dividing the sum by the # of values.

Standard Deviation

A measure of the amount of variation in a set of values.

Confidence Interval

A range of values that has a specified probability of containing the true value of a measurement.