Chemistry: An Atoms Focused Approach Chapter 1

Atoms

Tiny building blocks

Molecules

Groups of atoms held together in a characteristic pattern and proportion

Chemical bonds

What holds atoms together

Sublimation

Solid to gas

Deposition

Gas to solid

Energy

The ability to do work

Matter

Everything in the universe that has mass (m)

Solid

Definite volume and shape

Liquid

Definite volume but not a definite shape

Gas (vapor)

Neither definite volume or shape

Work (w)

The exertion of a force (F) through a distance (d)

Equation for work

w = F x d

Heat

Energy transfer where energy flows from a warm object to a cooler one

Chemical Reactions

One or more substances converted into one or more different substances

Potential Energy (PE)

Energy stored in an object because of its position or composition

Kinetic Energy (KE)

Energy of motion

Law of Conservation of Energy

Energy cannot be created or destroyed, only converted

Kinetic Energy equation

KD = 1/2mu^2

Symbol for speed

u

Pure Substance

matter that cannot be separated into simpler matter by a physical process

Physical Process

a 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

Element

A pure substance that cannot be separated into simpler substances by any chemical process

Compound

A pure substance that is composed of two or more elements linked together in fixed proportions and that can be broken down into those elements by some chemical process

Chemical Formula

a notation for representing the elemental composition of a pure substance using the symbols of the elements; subscripts indicate the relative number of atoms of each element in the substance

Law of Constant Composition

the principle that all samples of a particular compound always contain the same elements combined in the same proportions

Mixture

a combination of pure substance in variable proportions in which the individual substances retain their chemical identities and can be separated from one another by a physical means

Homogeneous Mixture

a mixture in which the components are distributed uniformly throughout and have no visible boundaries or regions

Solution

another name for a homogeneous mixture

Heterogeneous Mixture

a mixture in which the components are not distributed uniformly, so that the mixture contains distinct regions of different compositions

Immiscible Liquids

combinations of liquids that are incapable of mixing with, or dissolving in, each other

Distillation

a process using evaporation and condensation to separate a mixture of substances with different volatilities

Volatility

a measure of how readily a substance vaporizes

Filtration

a process for separating solid particles from a liquid or gaseous sample by passing the sample through a porous material that retains the solid particles

Chromatography

a process involving stationary and mobile phases for separating a mixture of substances based on their different affinities for the two types of phases

Intensive Property

a property that is independent of the amount of substance present (density, hardness)

Extensive Property

a property that varies with the amount of substance present (mass, volume)

Physical Property

a property of a substance that can be observed without changing the substance into another substance

Density (d)

the ratio of the mass (m) of an object to its volume (V)
d = m/V

Chemical Property

a property of a substance that can be observed only by reacting the substance chemically to form another substance

Scientific Method

an approach to acquiring knowledge based on observation of phenomena, development of a testable hypothesis, and additional experiments that test the validity of the hypothesis

Scientific Law

a concise and generally applicable statement of a fundamental scientific principle

Law of Definite Proportions

compounds always contain the same proportions of their component elements equivalent to the Law of Constant Composition

Scientific Theory

a general explanation of widely observed phenomena that has been extensively tested

Hypothesis

a tentative and testable explanation for an observation or a series of observations

Law of Multiple Proportions

when two masses of one element react with a given mass of another element to form two different compounds, the two masses of the first element have a ratio of two small numbers

Molecular Formula

a chemical formula that shows how many atoms of each element are in one molecule of a pure substance

Structural Formula

a representation of a molecule that uses short lines between the symbols of elements to show chemical bonds between atoms

Ball-and-Stick Models

Show bond angles, but make the atoms appear far apart

Space-filling models

More accurately show how the atoms are arranged in a molecule and its overall 3D shape, but it can be hard to see all the atoms and angles

Meter (m)

the standard unit of length; equivalent to 39.37 inches

Joule (J)

the SI unit of energy, equivalent to 1 kg(m/s)^2

pico

10^-12

nano

10^-9

micro

10^-6

milli

10^-3

centi

10^-2

deci

10^-1

deka

10^1

hecto

10^2

kilo

10^3

Precision

the extent to which repeated measurements of the same variable agree

Accuracy

agreement between an experimental value and the true value

Significant Figures

all the certain digits in a measured value plus one estimated digit. The greater the number of sig figs, the greater the certainty with which the value is known

Absolute Zero

zero point on kelvin temperature scale; theoretically the lowest temperature possible. -273 °C or -459 °F

0 °C

32 °F or 273 K

Conversion for °F to °C

°C = 5/9(°F-32)

Conversion for °C to K

K = °C + 273.15