Chapter 1 Gen Chem 1: Matter and Energy- An Atomic Perspective

Atoms

Tiny indestructible building blocks that retain the characteristics of that element; cannot make smaller mechanically or chemically

Elements

a pure substance that cannot be separated into simpler substances

Compounds

substance with two or more element types chemically bonded in a fixed proportion

Law of Multiple Proportions

when two elements combine to make two or more compounds; the ratio of the masses of one of the elements that combine with a given mass of the second element is always a ratio of small whole numbers

Matter

Everything that has mass and occupies space

Pure substances

matter that has a constant composition and cannot be broken down into simple matter by any physical process

Physical process/change

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

Compound

a pure substance composed of two or more elements that are chemically bonded in a fixed proportion

Physical properties

properties that can be observed without changing the substance into another substance

Extensive properties

a physical property that varies with the amount of substance; depends on how much of the substance is present in a particular sample

Examples of extensive properties

length, width, mass, volume

Extensive properties

a physical property that varies with the amount of substance; depends on how much of the substance is present in a particular sample

Examples of extensive properties

length, width, mass, volume

Density formula

d= m/V

What are the units for density?

g/mL for liquids

g/cm³ for solids

Intensive property

property dependent on the amount of the substance

Chemical properties

can be observed only by reacting the substance with something else to form another substance

Chemical reactions/change

conversion of one or more substances into one or more different substances

Chemical bonds

a force that holds two atoms or ions in a molecule or a compound together

Molecules

a collection of chemically bonded atoms

Ions

a particle consisting of one or more atoms that has a net positive or negative electrical charge

Mixtures

A combination of two or more pure substances in various proportions in which the individual substances retain their chemical identities and can be separated from one another by a physical process

What are the two kinds of mixtures

homogenous or heterogenous

Homogenous mixtures

mixture in which the components are distributed uniformly and the composition and appearance are uniform

Heterogenous mixtures

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

What are the processes for separating mixtures

distillation, filtration, chromatography

Distillation

uses evaporation and condensation to separate a mixture of substances that have different boiling points

Filtration

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

Chromatography

separates substances based upon their affinity for one phase or the other

What are the two types of pure substances?

element or compound

What are the states of matter?

solid, liquid or gas

Solid

Definite shape and volume; particles have an ordered structure 

Liquid

has a definite volume and takes shape of its container; particles are free to move past each other 

Gas

neither a definite volume or shape; particles have the most freedom and fill their container

Sublimation

transformation of solid to gas (energy absorbed)

Deposition

transformation from vapor to solid (energy released)

Melting

transformation from solid to liquid (energy absorbed)

Freezing (fusion)

transformation from liquid to solid (energy released)

Condensation

transformation of gas to liquid (energy released)

Vaporization

transformation of liquid to gas (energy absorbed)

Molecular formula

indicates how many atoms of each element are in one molecule of a pure substance; represents element present and how many of each element is in a molecule

Structural formulas

the connections between atoms and the arrangement of each element in a compound

Condensed structural formula

omit common structural components; atoms appear in a pattern (-CH3)

Ball and stick models

three dimensional representations of molecules

Space filling models

more accurately show how the atoms are arranged in a molecules and its overall three dimensional shape

Ionic compounds

A compound that consists of a characteristic ratio of positive and negative ions

Example of ionic compound

sodium chloride (NaCl)

Energy

capacity to do work

Work

transfer of energy to move an object over a distance

Work formula

w= F x d

Kinetic energy

the energy of an object in motion

Example of kinetic energy

release of glucose during a run

Kinetic energy formula

KE= ½ (mu²)

Potential energy

energy stored in an object because of its position or composition

Chemical energy

form of potential energy, stored in a molecule

Potential energy formula

k(Q1 Q2)/ d

Heat

Energy transferred because of a difference in temperatures; transfer from a warm object to a cool one

Law of Conservation of Energy

energy cannot be created nor destroyed but it can change from one form to another

SI units

a set of base and derived units used worldwide to express distances and quantities of matter and energy

Precision

How close repeated values are to each other

Accuracy

How close a measured value is to the true value

Significant figures

All certain digits in a measured value plus one estimated digit

Why is important to have a large amount of significant figures?

the greater the number of significant figures, the greater the certainty with which the value is known

Scientific methods

start with observations of natural phenomena and/or the results of laboratory experiments

Hypothesis

explains the observations and results

Scientific theory

explains all the results and observations available

Scientific law 

A comprehensive, succinct description of a phenomenon or process 

Law of definite proportions

A compound always contains the same proportion of its component elements 

Law of constant composition

A compound always has the same elemental composition by mass no matter what its source

What did Dalton’s atomic theory do?

explained Protust’s law of definite proportions and Dalton’s law of multiple proportions

What did Dalton observe when explaining Proust’s law?

When two elements react to form gaseous compounds, they may form two or more compounds with different compositions

What are the two kinds of matter?

A mixture or a pure substance 

What are the two classifications for pure substances?

either elements or compounds

What does a chemical formula do?

Indicates the proportion of elements in a substance

How can mixtures be separated?

Physical processes like distillation and filtration

What does a molecular formula indicate?

The composition of molecular compounds 

How are three dimensional arrangements of compounds represented?

structural formulas, ball and stick models, and space filling models

What does the empirical formula do?

Indicates the ratio of positive ions to negative ions

Measured quantities 

Uncertain 

Exact values

Derived from counting objects or values that are defined

What is the standard unit of length in SI?

meter

Conversion factors

Factors in which numerators and denominators have different units but represent the same quantity