Transcript Intro to Chem

Matter and Change
Chapter 2
Wilbraham, Antony C., Dennis D. Staley, Michael S. Matta, and Edward L. Waterman. Prentice Hall Chemistry. 1st ed. Upper Saddle River, NJ: Pearson Prentice Hall, 2008.
2.1 Properties of Matter

Describing Matter
◦ Properties used to describe matter can be
classified as extensive or intensive
 Extensive property – is a property that depends on
the amount of matter in a sample.
 Mass – a measure of the amount of matter the object
contains
 Volume – measure of the space occupied by the object
 Intensive property – is a property that depends on
the type of matter in a sample, not the amount.
 Hardness, color, texture, etc.

Identifying Substances
◦ Every sample of a given substance has
identical intensive properties because every
sample has the same composition.
 Substance – Matter that has a uniform and definite
composition.
 Physical property – a quality or condition of a
substance that can be observed or measured
without changing the substance’s composition.

States of Matter
◦ Three states of matter are solid, liquid, and
gas.
 Solid – a form of matter that has a definite shape
and volume
 Liquid – form of matter that has an indefinite shape,
flows, yet has a fixed volume.
 Gas – form of matter that takes both the shape and
volume of its container.

Solid
◦ Have definite shape and volume
◦ Particles are packed close/tight together in a form
held together by molecular forces.
◦ Divided into two categories
 Crystalline – orderly arrangement
 Iron, ice, and diamond
 Amorphous – no order
 Rubber and wax

Liquid
◦ Has a definite volume but no shape
◦ Take shape of the container they occupy.
◦ Particles are tightly packed together, but are
able to slide pass each other
◦ Particles move fast enough to overcome
molecular forces

Gas
◦ Are free to move in all directions
◦ Gases expand to fill a space.
◦ Particles move fast enough to break away
from each other
◦ Particles move rapidly

States of Matter Comparison Video
Physical Changes – some properties of a
material change, but the composition of
the material does not change.
 Physical changes can be classified as
reversible or irreversible.

◦ Reversible - Boil, freeze, melt, condense,
◦ Irreversible - break, split, grind, cut, and crush
Physical Properties describe Matter.
Color, shape, melting point, boiling point,
density, strength, hardness, ability to
conduct electricity, etc.
 Melting point – temperature and pressure
at which a solid becomes a liquid
 Boiling point – temperature at which a
liquid becomes a gas.
 Density – ratio of the mass of a substance
to the volume of a substance. D = M/V

2.1 Section Assessment
Page 42
1-8

2.2 Mixtures

Classifying Mixtures
◦ Mixture is physical blend of two or more
components.
 Chicken noodle soup
 Air
◦ Based on the distribution of their
components, mixtures can be classified as
heterogeneous mixtures or as homogeneous
mixtures.

Homogenous mixture (solution) – is a
mixture in which the composition is uniform
throughout.
◦ Stainless steel – mixture of iron, chromium, &
nickel.

Heterogeneous Mixtures
◦ A mixture in which the composition is not
uniform

Phase – used to describe any part of a
sample with uniform composition and
properties.
 Italian dressing. – oil phase floats on top of the water phase.

Separating Mixtures
◦ Differences in physical properties can be used
to separate mixtures.
◦ Filtration – separates a solid from the liquid in
a heterogeneous mixture.
 Water and sand
◦ Distillation – liquid is boiled to produce a
vapor that is then condensed into a liquid.
(see Fig 2.8, pg 47).
Distillation Process
Image from: http://www.rpdp.net/sciencetips_v3/images/p8a3/P8A3_clip_image012.jpg
Substance v. Mixtures
1.
2.
3.
4.
5.
6.
7.
8.
9.
Sodium
Water
Soil
Coffee
Oxygen
Alcohol
Carbon dioxide
Cake batter
Nail polish
10.
11.
12.
13.
14.
15.
16.
17.
18.
Air
Soup
Iron
Salt water
Ice cream
Nitrogen
Eggs
Blood
Table salt
Homogeneous v. Heterogeneous
1.
2.
3.
4.
5.
6.
7.
8.
Flat soda pop
Cherry vanilla ice
cream
Salad dressing
Sugar
Soil
Aluminum foil
Black coffee
Sugar water
9.
10.
11.
12.
13.
14.
15.
City air
Paint
Alcohol
Iron
Beach sand
Pure air
Spaghetti sauce.
Separation of Mixtures
1.
2.
3.
4.
5.
6.
7.
8.
Sand and water
Sugar and water
Oil and water
Sand and gravel
Mixture of heptane (boiling point 98°C) and
heptanol (bp 176°C)
Mixture of iodine solid and sodium chloride
(iodine not soluble in water)
Mixture of lead and aluminum pellets
Mixture of salt and iron filings.
2.2 Section Assessment

Page 46
◦ Problems 9 – 10

Page 47
◦ Problems 11 - 17
2.3 Elements and Compounds

Element – is the simplest form of matter
that has a unique set of properties.
◦ Oxygen (O2) Hydrogen (H2)

Compound – is a substance that contains
two or more elements chemically combined
in a fixed proportion.
◦ Water (H2O)

Compounds can be broken down into
simpler substance by chemical means, but
elements cannot.

Breaking Down Compounds:
◦ Physical methods that are used to separate
mixtures cannot be used to break a compound
into simpler substances.
◦ Chemical change is a change that produces matter
with a different composition than the orginal
matter.
 Sugar broken down into C and H2O(g) when heated.
 Broken down into H2 and O2 by passing a current
through

Properties of Compounds
◦ Compounds and the elements from which they
form have different properties.
◦ Chlorine (Cl2) is a poisonous gas, while sodium
(Na) is a extremely reactive solid, combined they
form NaCl, table salt.

Distinguishing Substances and Mixtures
◦ If the composition of a material is fixed, the
material is a substance.
◦ If the composition of a material may vary, the
material is a mixture.
Matter
Substance
Definite
composition
(homogeneous)
Element
Gold
Can be
separated
chemically
Mixture of
Substances (variable
composition)
Compound
Table Salt
Homogeneous
mixture/solution
Heterogeneous
mixture/nonuniform
Stainless Steel
Granite

Symbols and formulas
◦ Chemists use chemical symbols to represent
elements, and chemical formulas to represent
compounds.
◦ Chemical symbol – each element is represented by
one or a two letter symbol. 1st letter is always
captialized.
Section 2.3 Assessment
Page 52
 Problems 20 – 27.

2.4 Chemical Reactions
Chemical properties: burn, rot, rust,
decompose, ferment, explode, and
corrode, are used to describe a chemical
change.
 Chemical property – is the ability of a
substance to undergo a specific chemical
change.
 During a chemical change, the
composition of matter always changes.

Chemical reaction – is when one or more
substance change into one or more new
substances.
 A chemical reaction (rxn) has two parts the
reactants and the products.
 Reactant – substance present at the start of
the rxn
 Product – substance produced in the rxn.
 H2 + O2 → 2H2O


Recognizing Chemical Changes
◦ Possible clues to chemical change include a transfer
of energy, a change in color, the production of a
gas, or the formation of a precipitate.
◦ Precipitate – is a solid that forms and settles out of
a liquid mixture.
◦ The only way to know for sure if a chemical change
is to test the composition of the sample before and
after the change.
 pH, heat, bubbles (acid/base rxn),
Physical v. chemical properties
1.
2.
3.
4.
5.
6.
7.
8.
Red color
Density
Flammability
Solubility
Reacts with acid to
form hydrogen
Supports
combustion
Bitter taste
Melting point
9.
10.
11.
12.
13.
14.
15.
Reacts with water
to form a gas
Reacts with a base
to form water
Hardness
Boiling point
Can neutralize a
base
Luster
Odor
Physical v. Chemical Change
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Sodium hydroxide dissolves in water
Hydrochloric acid reacts with sodium
hydroxide to produce a salt, water and heat
A pellet of sodium is sliced in two
Water is heated and changed to steam
Potassium chlorate decomposes to potassium
chloride and oxygen gas.
Iron rusts.
Ice Melts
Acid on limestone produces carbon dioxide
gas.
Milk sours.
Wood rots.

Conservation of Mass
◦ During any chemical rxn, the mass of the products
is always equal to the mass of the reactants.
◦ Law of Conservation of Mass – states that in any
physical change or chemical rxn, mass is conserved.
2.4 Section Assessment
Page 55
 Problems 28 - 34
