Transcript Chapter 3: Matter-Properties and Changes

Chemistry
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Substances (Pure Substance)
◦ Matter that has a uniform and unchanging
composition
◦ Table Salt, Water
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Physical Property- a characteristic that can be
observed and measured without changing the
samples
◦ Hard, soft, shiny, dull, brittle, flexible heavy, light,
density, freezing point, boiling point, etc.
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Extensive Properties- dependent upon
amount of substance
◦ Length, volume
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Intensive Property- independent of amount of
substance.
◦ Density (at constant pressure and volume),
appearance
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Chemical Property- ability of a substance to
combine with or change into one or more
substances
◦ Iron forms rust with air, gold’s inability to combine
with most other substances
a) Silver tarnishes when it comes in contact
with hydrogen sulfide in the air
b) A sheet of copper can be pounded into a
bowl
c) Barium melts at 725oC
d) Helium does not react with any other
element
e) A bar of lead is more easily bent than is a
bar of aluminum of the same size
f) Potassium metal is kept submerged in oil to
prevent contact with oxygen or water
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Solids
◦ Has definite shape and volume
◦ Rigid and incompressible
◦ Particles packed closely together and held in a
specific arrangement
◦ Expands slightly when
heated
◦ Wood, Iron, Paper, Sugar
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Liquids
◦ Matter that flows (moves)
◦ Has constant volume, takes shape of its container,
but does not fill container
◦ Particles not rigidly held in place, less closely
packed together (than solids)
◦ Particles not in specific
arrangement
◦ Mostly incompressible
◦ When heated tend to expand
◦ Water, Blood, Mercury
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Gases
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Flows to conform to the shape of its container
Fills entire volume of container
Particles very far apart, freely moving
Easily compressible
Air, Neon, Methane,
Helium
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Gas… something naturally in gaseous state at
room temperature
◦ Air, Helium
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Vapor… something that is normally a solid or
liquid at room temperature
◦ Steam (At room temperature water is a vapor)
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Identify each of the following as a property of
a solid, liquid, or gas
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Flows and takes the shape of its container
Compressible
Made of particles held in a specific arrangement
Has a definite volume
Always occupies the entire space of its container
Has definite volume but flows
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Physical Changes- alters a substance without
changing its composition (what it is)
◦ Examples: liquid-water, solid-ice, gas-steam
◦ Terms like…bend, grind, crumple, split, crush, boil,
freeze, vaporize, melt, etc
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Chemical Changes- process that involves one
or more substance changing into new
substance…Chemical reaction
New Substance has different properties form
old substances
◦ Example: iron reacts with air to form iron oxide
(rust), striking a match, battery to steel wool
◦ Terms like…explode, rust, oxidize, corrode, tarnish,
ferment, burn, or rot
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Staring substances called reactants, new
substances called products
Chemical Equation-shows relationship
between reactants and products in chemical
reaction
◦ Example: iron + oxygen → rust
(reactants)
(product)
a) Moisture in the air forms beads of water on a
cold window pane
b) An electric current changes water into hydrogen
and oxygen
c) yeast cells in bread dough makes carbon dioxide
and ethanol from sugar
d) olive oil, vinegar, salt, and pepper are shaken
together to make salad dressing
e) Molten bronze is poured into a mold and
solidifies to form a figurine
f) A reactant decomposes to form 2 products
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Law of Conservation of Mass-during a chemical
reaction mass is neither lost or gained
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Mass
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Reactants
= Mass
Products
Example: A thin strip of iron with a mass of
15.72g is placed into a solution containing
21.12g of copper (II) sulfate and copper begins to
form. After a while, the reaction stops because
all of the copper (II) sulfate has reacted. The iron
strip if found to have a mass of 8.33g. The mass
of copper formed is found to be 8.41g. What
mass of iron (II) sulfate as been formed in the
reaction?
1) A sealed glass tube contains 2.25g of
copper and 3.32g of sulfur. The mass of the
tube and its contents is 18.48g. Upon
heating, a reaction forms copper (II) sulfide
(CuS). All of the copper reacts, but only
1.14g of sulfur reacts. Predict what the mass
of the tube and its contents will be after the
reaction is completed. Explain your
reasoning.
2) A reaction between sodium hydroxide and
hydrogen chloride gas produces sodium
chloride and water. A reaction o 22.85g of
sodium hydroxide with 20.82g of hydrogen
chloride gives off 10.29g of water. What
mass of sodium chloride is formed in the
reaction?
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Mixture: a combination of two or more
substances where the pure substance retain
chemical properties (Physically Combined)
◦ Heterogeneous mixture- does not blend smoothly
(individual substance remain distinct)
 Sand and water, oil and water, pizza, muddy water,
smoky air
◦ Homogeneous mixture- constant composition
throughout, has single phase
 Salt-water, gasoline, cough suppressant, pure air
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Solutions- homogeneous mixture
The atoms/molecules of two (or more)
substances are completely mingled with one
another
Alloy: homogeneous mixture of tow or more
metals, or of metals and nonmetals
◦ Solid solutions
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70% isopropyl rubbing alcohol
A pile of rusty iron filings
Concrete
Saltwater
Gasoline
Bread
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Physical separation- separation by physical
means
◦ Sand-iron: separate using a magnet
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Filtration- uses a porous barrier (filter paper)
to separate solid from liquid
◦ Sand-water: separate using filter paper
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Distillation: uses differences in boiling points
◦ Table salt-water: boiling out the water
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Crystallization: results in the formation of
pure solid particles of a substance from
solution containing the dissolved substance
◦ Rock Candy
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Chromatography- separates the components
of a mixture (called the mobile phase) on the
basis of the tendency of each to travel across
a surface (called stationary phase)
◦ Ink separation
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Matter: classified as pure substance or
mixture (homogeneous or heterogeneous)
Pure substance:
◦ Element
◦ Compound
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Element: pure substance that cannot be
separated into simpler substances by physical
or chemical means
◦ Example: Copper, Oxygen, and Gold
◦ Have unique name and symbol
◦ 91 element occur naturally on Earth, 110 altogether
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Dmitri Mendeleev (1869)
◦ Organized (know ones at time) the element into
rows and columns based on their similarities
◦ Considered to be innovative, due to fact that his
chart could account for elements that were not yet
discovered
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Vertical Columns: called groups or families
(have similar properties)
Horizontal Rows: called periods (repeat the
properties of the elements above them)
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Compounds: a combination of two or more
different elements that are combined
chemically
◦ Examples: Water, Table Salt, Table Sugar, and
Aspirin
◦ Chemical symbols of the Periodic table make it easy
to write formulas for chemical compounds
◦ Example: H2O (water), NaCl (salt), NH3 (ammonia)
◦ Can be broken down into simpler substances by
chemical means
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Compounds are usually more stable than the
individual elements they are composed of
Properties of a compound are different from
those of the elements it is made from
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Identify each of the following as an example
of an element or compound
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Sucrose (table sugar)
The helium in a balloon
Baking soda
A diamond
Aluminum foil
The substances listed on the periodic table
Calcium chloride pellets used to melt ice
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States that, regardless of the amount, a
compound is always composed of same
elements in the same proportion by mass
Example: 100.00g of H2O always contains
11.19g of hydrogen and 88.81g of oxygen
(no matter where the water came from)
Compounds can be identified from their
percent composition or percent by mass
Percentby Mass 
mass of element
100
mass of compound
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Law of multiple proportions: states that when
different compounds are formed by the
combination of the same elements, different
masses of one element combine with the
same mass of the other elements in a ratio of
small whole numbers
Examples: Water (H2O) and hydrogen
peroxide (H2O2), the hydrogen parts are equal
and the oxygen parts are not, oxygen has 1:2
ratio between the two compounds.
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A 134.50g sample of aspirin is made up of
6.03g of hydrogen 80.70g of carbon, and
47.77g of oxygen. What is the percent by
mass of each element in aspirin?
A 2.89g sample of sulfur reacts with 5.72g of
copper to form a black compound. What is
the percentage composition of the
compound?