Download PS Unit 2 PowerPoint rev 2011

Unit 2
Distinguish chemical properties of matter (including reactivity) from physical properties of matter
(including boiling point, freezing/melting point, density [with density calculations], solubility,
viscosity, and conductivity). (PS-3.1)
Infer the practical applications of organic and inorganic substances on the basis of their chemical and
physical properties. (PS-3.2)
Illustrate the difference between a molecule and an atom. (PS-3.3)
Classify matter as a pure substance (either an element or a compound) or as a mixture (either
homogeneous or heterogeneous) on the basis of its structure and/or composition. (PS-3.4)
Compare the properties of the four states of matter—solid, liquid, gas, and plasma—in terms of the
arrangement and movement of particles. (PS-3.6)
Explain the processes of phase change in terms of temperature, heat transfer, and particle
arrangement. (PS-3.7)
States of Matter
• Solids
• Particles held together by strong attractions
• Vibrate in place
• Definite shape & volume
• Liquids
• Particles move fast enough to overcome attractions and
move past each other
• Take shape of container
• Volume cannot change because particles are close
together
States of Matter
• Gases
• Particles move fast enough to break all
attractions
• Expand to fill available space
• Plasma
•
•
•
•
No definite shape or volume
Particles are electrically charged
Conducts electricity
Found in lightning, fire & aurora borealis
States of Matter
Phase Changes
Kinetic Molecular Theory
• All matter is made up of constantly moving
particles.
• In order for a substance to be a liquid or a solid at
room temperature there has to be some force of
attraction between the particles that make up the
substance.
Kinetic Molecular Theory
• Different types of intermolecular forces of
attraction:
• Dispersion forces
• Dipole-dipole
• Hydrogen bonding
• Important in biological functions
• Keeps H2O molecules in liquid state at room temp
Kinetic Molecular Theory
• Kinetic energy is energy of moving things
• At a given temperature the average kinetic energy of
particles is the same.
• Temperature is a measure of average kinetic energy.
• The higher the temperature the higher the average
kinetic energy and vice versa.
Phase Changes
• During a change in state (i.e. solid → liquid)
• Energy is being added to the substance
• Endothermic
• Temperature stays constant because the energy is going
into the atoms/particles to change the state of the
substance.
• IMAs are becoming weaker
Phase Changes
• During a change in state (i.e. liquid → solid)
• Energy is being removed from the substance
• Exothermic
• Temperature stays constant because the energy is being
removed from the atoms/particles
• IMAs are becoming stronger
Phase Changes
Boiling – add
heat; temp
constant;
weakening IMAs
Melting – add heat;
temp constant;
weakening IMAs
Liquid – add heat;
increase temp
Solid – add heat;
increase Temp
Gas – add
heat; increase
temp
Physical v. Chemical Properties
• Physical Properties:
• Can be observed without changing the chemical
makeup of a substance
• Examples: solubility, mass, volume, MP, BP, color,
hardness, conductivity, heat capacity
• Chemical Properties:
• Describes a chemical change & the kinds of chemical
reactions that a substance undergoes
• Examples: reactivity with H2O or air, reaction to being
heated or cooled, exposed to sunlight, or mixed w/
another substance
Extensive v. Intensive Properties
• Extensive properties
• Properties that depend on sample size
• Examples: Mass, volume
• Intensive properties
• Properties that are independent of sample size
• Examples: density, electrical conductivity
Identification of Substances
• Intensive properties more useful
•
•
•
•
Density
Boiling point
Melting point
Color
• Chemical properties such as reactivity with
oxygen when heated also useful (real gold
v. fool’s gold)
Density
• Physical, intensive property
• Ratio of an object’s mass to its volume
• D = m/V
• Decreases slightly with increasing temperature
(except for water)
• 3 methods for finding volume of object:
• l x w x h (rectangular prisms)
• Water displacement (oddly shaped solids)
• Use graduated cylinder (for liquids)
Mixtures
• Combination of 2 or more pure substances in
which each substance keeps individual chemical
properties
• Heterogeneous mixtures
• Not blended evenly, separate substances remain distinct
• Homogeneous mixtures
• Constant composition throughout; always has single
phase
• Also called solutions
Separation Techniques
• Mixtures can be separated by
differences in physical
properties.
• Centrifugation (using a
centrifuge)
• Separates mixtures of
undissolved solids from liquids
by density.
• As the centrifuge spins the
mixture, the larger particles
fall to the bottom of the
centrifuge tube.
• This is how platelets are
separated from the liquid
portion of your blood at
medical laboratories.
Separation Techniques
• Distillation:
• Separates mixtures of
liquids by boiling
point.
• A heating mantle
would be held on the
ring clamp on the left
in order to heat the
mixture to the boiling
point of the liquid to be
recovered.
Separation Techniques
• Filtration :
• Separates mixtures of
undissolved solids from
liquids by particle size.
• The filter can be paper as
shown above, or a synthetic
membrane, as shown on the
below.
• The solid particles in a
mixture are trapped on the
filter, and the liquid portion
(the filtrate) is collected in a
receiving flask, beaker, or
other suitable container.
Separation Techniques
• Chromatography:
• Separates mixtures based on
attractive forces between the
particles of two different
phases. (solubility)
• The more the component is
attracted to the mobile phase
(the liquid moving up the
paper) the higher the
component travels up the
paper.
• The more the component is
attracted to the stationary
phase (the paper which is not
moving) the more it is retained
or held back by the paper.
Elements & Compounds
• Element:
• Pure substance that cannot be separated into simpler
substances by physical or chemical means
• Periodic Table: organizes elements based on
physical and chemical properties
• Compound:
• combination of 2 or more elements that are combined
chemically
• Properties of cmpd differ from those of elements (salt
and water)