Transcript Matter & Energy - Dr. RICK MOLESKI

Matter & Energy
Introduction
Another View
Classifying Matter According to its State:
Solid, Liquid, Gas
• Water can exist as a solid, liquid or gas
Classifying Matter According to its State:
Kinetic Theory
Compressibility
• Solids are incompressible
• Gases are compressible
• Liquids are very slightly
compressible – usually
considered incompressible
Types of Solid Matter
• Crystalline Solids
– Long-range order
– Repeating patterns
- Sodium Chloride
• Amorphous Solids
– No long range order
– Polymers, glass
Which of the following does not describe the
gaseous state?
a. Same shape as a closed container
b. Same volume as a closed container
c. Random, independent particle movement
d. Easily compressed
e. All describe the gaseous state
Which of the following does not describe the liquid
state?
a. Particles vibrate in fixed position
b. Same shape as the bottom of the container
c. Constant volume
d. Can be poured
e. All describe the liquid state
Which of the following does not describe the solid
state?
a. Rigid, fixed, constant shape
b. Constant volume
c. Easily compressed
d. Particles vibrate in fixed position
e. All describe the solid state
Physical Change
C3H8 (l)  C3H8 (g)
Chemical Change
C3H8(l) + O2(g) CO2(g) + H2O(l)
How do chemists describe/identify a
substance?
1. Physical properties:
– Appearance, hardness, odor
– Density, viscosity, electrical
conductivity, boiling point,
melting point
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Physical changes – change the
physical form of matter without
changing its chemical identity
– Melting ice
– Dissolving sugar in water
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Name a physical property that
changes during the melting of ice
Some Physical Properties
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Phase (solid, liquid, gas)
Mass
Volume
Density
Melting Point
Boiling Point
Volatility
Specific Heat Capacity
Malleability
Ductility
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Taste
Odor
Color
Texture
Shape
Solubility
Electrical Conductance
Thermal Conductance
Magnetism
Phase Changes – require heating or cooling
the substance
• Melting: solid  liquid
• Boiling: liquid  gas
• Subliming: solid  gas
• Freezing: liquid  solid
• Condensing: gas  liquid
• Deposition: gas  solid
An example of sublimationcrystals of iodine changing to vapor
I2(s)  I2(g)
How do chemists describe/identify a
substance?
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Chemical changes – the
chemical identity of a substance
is destroyed and a new
substance(s) is formed
– Rusting of iron
– The fading of a t-shirt with
exposure to sunlight
2. Chemical properties: describe
reactivity, i.e. Flammability
Chemical Changes involve the
rearrangement of the way atoms are bonded
• Methane reacts with oxygen to produce water and carbon dioxide
• Reactants: oxygen and methane
• Products: water and carbon dioxide
Some Chemical Properties
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Acidity
Corrosiveness
Reactivity
Inertness
Flammability
Oxidizing Ability
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Basicity (aka Alkalinity)
Stability
Explosiveness
Combustibility
Reducing Ability
Determining Whether a Change is
Chemical or Physical
• Both involve changes in physical appearance
• Physical changes are reversible
• Potassium
chromate
• Ammonium
dichromate
 ammonia
+ water +
chromium
(III) oxide
Evidence of Chemical Changes
• What do you notice?
• Which observations could also
be noticed during a physical
change?
None as the bubbles in (a) are escaping hydrogen
gas
Which of the following properties is/are classified as
chemical?
a. the taste of honey
b. the ability of hair to stretch
c. the corrosive character of hydrochloric acid
d. the combustibility of ethanol
e. the softness of talc
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a)
b)
c)
d)
e)
f)
g)
h)
i)
Classify each of the following changes as
physical or chemical
grape juice turns to wine
wood burns to ashes
a broken leg heals itself
grass grows
an infant gains 10 pounds
a rock is crushed to powder
baking soda fizzes in vinegar
vinegar and oil separate into two layers
helium balloon decreases in size
Classifying Matter According to its Composition:
Elements, Compounds, & Mixtures
Matter
Pure Substances
Mixtures
• Pure Substance – composed of one type of atom or molecule
– Own set of physical and chemical properties
• Mixtures – composed of two or more different types of atoms
or molecules in variable proportions
– Physical and chemical properties vary with the proportions
of the components of the mixture
Matter
Pure Substances
• Pure Substance
– Own set of physical and
chemical properties
• Mixtures
– Physical and chemical
properties vary with the
proportions of the
components of the mixture
Mixtures
Classify each of the following as a pure
substance or mixture
a)
b)
c)
d)
e)
gold
air
chunky peanut butter
sugar completely dissolved in water
ice
Classifying Matter According to its Composition:
Elements, Compounds, & Mixtures
Matter
Pure Substances
Elements
Compounds
Mixtures
Classifying Matter According to its Composition:
Elements
Matter
Pure Substances
Elements
Compounds
• Elements can not be broken
down into simpler substances,
i.e. silver (Ag)
Mixtures
Periodic Table
Classifying Matter According to its Composition:
Compounds
Matter
Pure Substances
Elements
Compounds
• Compounds – substance composed
of two or more elements in fixed
proportions, i.e. H2O & CO2
Mixtures
Classifying Matter According to its Composition:
Elements, Compounds, & Mixtures
Matter
Pure Substances
Elements
Compounds
Mixtures
Homogeneous
Heterogeneous
Classifying Matter According to its Composition:
Mixtures
Matter
Pure Substances
Elements
Compounds
Mixtures
Homogeneous
Heterogeneous
• Heterogeneous Mixtures – oil & water, sand & gravel, composition is
not uniform. 2 separate samples would yield varying amounts of
the components
• Homogeneous – Sugar dissolved in water. Uniform composition.
separate samples would yield the same ratio of components
2
A Microscopic View
Matter
Pure Substances
• Pure Substance
– Own set of physical and
chemical properties
• Mixtures
– Physical and chemical
properties vary with the
proportions of the
components of the mixture
• We can take advantage of the
different physical properties of
a mixture to separate the
components.
Mixtures
Separation of Mixtures
• Methods based on physical properties
Filtration – based on size
Distillation – based on boiling point
Separation of Compounds
• Methods based on chemical
changes
• 2H2O(l)  2H2(g) + O2(g)
• Involve the rearrangement of the
way atoms are bonded
• New compounds or elements are
formed
Electrolysis of water
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a.
b.
c.
d.
e.
When water boils, you can see bubbles rising to the
surface of the water. Of what are these bubbles made?
air
hydrogen and oxygen gas
oxygen gas
water vapor
carbon dioxide gas
Mixture Separation
• How could I separate a mixture of
sugar and sand?
We have a mixture of sawdust (wood chips),
copper, iron and salt
• We want to three separate piles
• ID Physical properties of components –
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• Separating different compounds:
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