Matter

Learning objectives

Classify material properties as extensive properties, intensive properties, chemical properties, and physical properties. Give examples of each. Quiz
Distinguish between gases, liquids, and solids. Explain how these states differ at the molecular level.
Classify samples of matter as pure substances, homogeneous mixtures, heterogeneous mixtures, compounds, and elements. Quiz
Use sketches to show how elements, compounds, and mixtures differ at the molecular level.
Describe six different techniques for separating mixtures.
Relate the names of elements to their international element symbols.
Describe the periodic table. Name the major groups and regions on the periodic table, and identify elements belonging to these groups.
Distinguish between metals, nonmetals, and metalloids using the periodic table.

Lecture outline

This lecture introduces some of the basic vocabulary and notation that will be used in the remainder of the course. Classification of matter and technologies for separating mixtures are discussed.

Quiz Quiz
Classifying properties as extensive/intensive or chemical/physical

Properties of Materials

describe materials by listing their properties
chemical properties vs. physical properties.

intensive properties

vs. extensive properties

Classifying properties as extensive or intensive. Extensive properties change when sample size changes; intensive properties don't.

Beaker w/100 mL water Beaker w/10 mL water

Mass of water 100.0 g 10.0 g

Volume of water 0.100 L 0.010 L

Temperature of water 25 °C 25 °C

Density of water 1.00 g/mL 1.00 g/mL

Classifying properties as extensive or intensive. Extensive properties change when sample size changes; intensive properties don't.

Mass of water	100.0 g	10.0 g
Volume of water	0.100 L	0.010 L
Temperature of water	25 °C	25 °C
Density of water	1.00 g/mL	1.00 g/mL

States of Matter

Gas	Liquid	Solid

low density easy to expand/compress fills container	high density hard to expand/compress takes shape of container	high density hard to expand/compress rigid shape

A phase is a region with homogeneous (uniform) properties
conversions between states are called "phase transitions" or "changes of state"

Classification of matter

uniform properties?	yes	fixed composition?	yes	chemically decomposable?	yes	compound
no		no		no
heterogeneous mixture		homogeneous mixture		element

Quiz
Classifying matter

Pure substances

characteristics
- percentage composition always the same from sample to sample
- melt/boil at a characteristic temperature
  - note: some compounds decompose before melting or boiling!
two types

elements not chemically decomposable into other elements properties do not vary
compounds elements combined chemically in law of definite proportions properties do not vary

Elements

modern definition: elements are made of atoms that all have the same atomic number
obtaining elements from compounds involves chemical change
- electrolysis decomposes some compounds into elements
- some elements displace others from compounds

writing element symbols

first 1-2 distinguishing letters in name used for symbol
only the first letter is uppercase!

memorize symbols derived from ancient names: Table 11 element symbols derived from ancient names.

English name	symbol	ancient name
antimony	Sb	stibium
copper	Cu	cuprum
gold	Au	aurum
iron	Fe	ferrum
lead	Pb	plumbum
mercury	Hg	hydrargyrum
potassium	K	kalium
silver	Ag	argentum
sodium	Na	natrium
tin	Sn	stannum
tungsten	W	wolfram

Classification of elements

periodic table compactly shows relationships between elements
features of the periodic table
- Periods are horizontal rows on the table.
- Groups (or families) are columns on the table.
  - elements in the same group are called congeners. They have similar chemical properties.
- Blocks are regions on the table.
important groups:
- alkali metals (Group IA, first column )
  - soft, extremely reactive metals
  - react with cold water to form hydrogen gas
  - form +1 ions
- alkaline earth metals (Group IIA, second column):
  - soft, reactive metals
  - compounds are a major component of earth's crust
  - form +2 ions
- halogens (Group VIIA, next-to-last column):
  - poisonous and extremely reactive nonmetals
  - fluorine and chlorine are yellow-green gases
  - bromine is a volatile red-brown liquid
  - iodine is a volatile blue black solid
  - all form -1 ions
- noble gases (Group 0, last column)
  - all are monatomic gases
  - a. k. a. inert gases; almost completely unreactive
Important blocks:
- transition metals are the elements in the region from the third to twelfth columns.
  - hard, dense metals
  - less reactive than Group IA and IIA
- rare earth metals are the elements in the annex at the bottom of the table.
  - lanthanides (annex, top row)
  - actinides (annex, bottom row)
- main group elements are all elements except the transition and rare earth metals.
  - group numbers end with "A"
- metals, nonmetals, and metalloids (semimetals)
  - metallic properties
    - luster
    - malleability: can be hammered into thin sheets
    - ductility: can be drawn into wire
    - conduct heat and electricity well

Allotropes

one element can occur in several different forms ( allotropes)

Common allotropes of oxygen and carbon. The most stable form at room temperature and pressure is shown in boldface.
element	allotrope
oxygen	O, nascent oxygen
	O₂, oxygen gas
	O₃, ozone
carbon	graphite
	diamond

gaseous elements commonly occur as diatomic molecules (except for the noble gases)

Mixtures

characteristics
- percentage composition varies from sample to sample
- components are chemically different and retain properties in a mixture
- do not melt/boil at a definite temperature
two types
heterogeneous mixtures

components not uniformly mixed
more than one phase
homogeneous mixtures

components uniformly mixed
one phase
also called solutions

How separation technology was used to solve a deadly mystery

Separating mixtures

mixture's components have different properties
devise a process that selects components with certain properties
- density, melting point, boiling point, solubility, reactivity, magnetism, polarity
some basic techniques
- filtration: select components by particle size
- floatation: select components by density
- crystallization: select components by solubility
- extraction: select components by solubility
- distillation: select components by boiling point
- chromatography: select components by affinity for a 'stationary phase'

General Chemistry Online! Matter

heterogeneous mixtures components not uniformly mixed more than one phase
homogeneous mixtures components uniformly mixed one phase also called solutions