Matter

Properties of Materials

o describe materials by listing their properties o chemical properties vs. physical properties. o intensive properties vs. extensive properties.

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

o low density o easy to

expand/compress o fills container

o high density o hard to

expand/compress o takes shape of

container

o high density o hard to

expand/compress o rigid shape

o A phase is a region with homogeneous (uniform) properties o 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

Pure substances

o characteristics percentage composition always the same from sample to sample melt/boil at a characteristic temperature

note: some compounds decompose before melting or boiling!

o 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 o electrolysis decomposes some compounds into elements o some elements displace others from compounds

writing element symbols o first 1-2 distinguishing letters in name used for symbol o only the first letter is uppercase! o 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 Argentums

sodium Na Natrium

tin Sn Stannum

tungsten W Wolfram

Classification of elements

periodic table compactly shows relationships between elements

features of the periodic table o Periods are horizontal rows on the table. o Groups (or families) are columns on the table.

elements in the same group are called congeners. They have similar chemical properties.

o Blocks are regions on the table.

important groups: o alkali metals (Group IA, first column )

soft, extremely reactive metals react with cold water to form hydrogen gas form +1 ions

o alkaline earth metals (Group IIA, second column): soft, reactive metals compounds are a major component of earth's crust form +2 ions

o 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

o noble gases (Group 0, last column) all are monatomic gases a. k. a. inert gases; almost completely unreactive

Important blocks: o transition metals are the elements in the region from the third to twelfth columns.

hard, dense metals less reactive than Group IA and IIA

o rare earth metals are the elements in the annex at the bottom of the table. lanthanides (annex, top row) actinides (annex, bottom row)

o main group elements are all elements except the transition and rare earth metals. group numbers end with "A"

o 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 o percentage composition varies from sample to sample o components are chemically different and retain properties in a mixture o do not melt/boil at a definite temperature

two types

o heterogeneous mixtures components not uniformly mixed more than one phase

o homogeneous mixtures components uniformly mixed one phase also called solutions

Separating mixtures

mixture's components have different properties

devise a process that selects components with certain properties o density, melting point, boiling point, solubility, reactivity, magnetism, polarity

some basic techniques o filtration: select components by particle size o floatation: select components by density o crystallization: select components by solubility o extraction: select components by solubility o distillation: select components by boiling point o chromatography: select components by affinity for a 'stationary phase