Transcript Chapter 2 Power Point

Unit 1
Chapter 2-pg38
Matter and Change
Chemistry 334
Essential Question:
 How do chemists classify matter?
Section 2.1
Properties of Matter
Describing Matter
KC: How can Properties be used to describe matter?
A: Properties used to describe matter can be classified
as ether extensive or intensive.
Extensive Properties
 A property that depends on the amount of matter in a
sample.
Examples of extensive
properties:
 Mass—the amount of matter an object contains.
 Volume—the measure of the space occupied by an
object.
Intensive Properties:
 A property that depends on the type of matter in a
sample, not the amount.
 Examples




Hardness
Odor
Conductivity
State of matter
*******What it is made of******
Identifying Substances
 KC: Why do all samples of a substance have the same
intensive properties?
 Every sample of a given substance has identical
intensive properties because every sample has the
same composition.
Substance
 Matter that has definite and uniform composition.
 AKA: Pure substance
 Examples:




Au
Ag
NaCl
CH4
NaCl vs. NaCl Water (H2O)
 Q: Is salt water a pure substance????
 INDEX CARD CHALLENGE!!!!
INDEX CARD CHALLENGE
 Without talking, find someone who has a different
answer that you
 IDK—does not count as an answer!!!
 Explain why you chose this answer.
The Answer
 NaCl is a pure substance
 Salt water is not
 It can have variable composition
Physical Properties
 Physical property—any quality or condition of a
substance that can be observed without changing the
substance’s composition.
 Examples:




State
Mp
Bp
Color
States of matter:
 KC: What are 3 states of matter?
 A: Three states of matter are solid, liquid, gas.
Solid
 Definite shape
 Definite volume
 Not easily compressed
Liquid
 Indefinite shape
 Definite volume
 Not easily compressed
Gas
 Indefinite shape
 Indefinite volume
 Easily compressed
Three States of Matter
Vapor
 Describes the gaseous state of a substance that is
generally a liquid or solid at room temperature.
Physical Changes
 KC: How can physical changes be classified?
 A: Physical changes can be classified as reversible or
irreversible.
Reversible
 Phase changes





Melting
Freezing
Sublimation
Boiling
Condensation
Irreversible
 Breaking
 Tearing
 Smashing
 Cutting
Section 2.2
Mixtures
Page 44
Classifying Mixtures
 KC: How can mixtures be classified?
 A: Mixtures can be calssified as either hetterogenous
or homogenous.
Mixture
 A combination of two or more pure
substance.
Can be made with different
combinations of solid, liquids and
gasses.
2 Types of mixtures
 1. Homogenous
 2. Heterogenous
Heterogeneous Mixture
 Not the same through out
 More than one phase
(distinguishable parts)
 ie:
 Chicken noodle soup
 Chex mix
Homogenous mixture
 Uniform composition; same through out
 AKA: Solution
 Only one phase
 ie:





Salt water
Tea
Olive oil
Vinegar
Alloy
Separating Mixtures
 KC: How can mixtures be seperated?
 A: Differences in physical properties can be used to
separate mixtures.
5 ways to separate mixtures
1. Filtration
2. Distillation
3. Crystallization
4. Sublimation
5. Chromatography
Filtration
 A technique which uses a pours barrier to separate a
solid from a liquid
Distillation
 A separation technique that is based on the differences
in the boiling points of the mixed substances
Crystallization
 A separation technique that results in the formation of
pure solid particles of a substance from a solution
containing the dissolved substance.
Sublimation
 The process during which a solid changes to a vapor
without going through the liquid phase
Chromatography
 A technique that separates the components of a
mixture (aka-mobile phase), based on the ability of
each component to be drawn across the surface of
another material (aka-stationary phase).
Section 2.3
 Elements and Compounds
Distinguishing Elements and
Compounds
 KC: How are elements and compounds different?
 A: Compounds can be broken down into simpler
substances.
Examples of elements
 Ca
 Na
 H
Periodic Table
 Organizes the elements into a grid of horizontal rows
(aka-periods) and vertical columns (akagroups/families).
Compounds
 Two or more elements combined chemically
Breaking Down Compounds
 Compounds can be broken down by chemical change
 This process usually requires a an external energy
source, such as heat or electricity
Properties of Compounds
 The chemical and physical characteristics of a
compound is very different than that of its constitute
parts.
Example:
 K + I  KI
Potassium & Iodine VS Potassium iodide
Potassium
 A light silver metal that reacts with water
Iodine
 A black solid that changes to a purple gas at room
temperature.
Potassium iodide
 A white salt
Distinguishing Substances
and Mixtures
 KC: How can substances and mixtures be
distinguished?
 A: If the composition of a material is fixed, the material
is a substance. If the composition of the substance
may vary, the material is a mixture.
Classification of matter
Ex: chex
mix
salt
water
(AKA: solutions)
NaCl
Na
Symbols and formulas
 KC: What do chamists use to represent elements and
compounds?
 A: Chemists use chemical symbols to repersent
elenents and chemical formulas to represent
compounds
Chemical Symbol
One or two letters used to represent the name of an
element.
Chemical Compounds
Section 2.4
 Chemical Reactions
Chemical Changes
 Key Concept: What always happens during a chemical
change?
 Answer: During a chemical change, the composition of
matter changes
 Example
combustion reaction
Examples:
 Fe to Rust
 Respiration
 Combustion (candle burning vs. wax
melting)
Words that indicate a chemical
change:
-Decompose
-Ferment -Tarnish
-Oxidize
-Burn
-Rust
-Corrode
-Rot
-Explode
Chemical Properties=
 The ability (or inability) of a
substance to combine with or
change into one or more
substances.
Chemical Change
 One or more substances changes into one or more
new substances.
 AKA: Chemical reaction
 Mg + HCl  H2 + MgCl
Reactants
 The substance that are to be transformed.
Product
 The substance(s) that are made
Recognizing Chemical
Changes
 Key Concept: What are the 4 possible clues that a
chemical change has taken place?
 Answer: Possible clues that a chemical reaction has
taken place include: transfer of energy (heat or light), a
change in color, the production of gas, or the formation
of a precipitate.`
Precipitate=
 The production of a solid.
Conservation of Mass
 Key concept: How are the masses of the reactants and
the masses of the products of a reaction related?
 Answer: During any chemical reaction the mass of the
reactants is always equal to the mass of the products.
Law of Conservation of Mass:
Massreactants=Massproducts
Practice Problems
2Mg + O2  2 MgO
Mass of Magnesium
(g)
Mass of Oxygen
(g)
Mass of Magnesium
oxide (g)
5
3.3
8.3
6.5
A
10.8
13.6
9
B
C
12.5
31.5
Words that indicate a chemical
change:
-Decompose
-Ferment -Tarnish
-Oxidize
-Burn
-Rust
-Corrode
-Rot
-Explode
Physical Changes=
 A change which alters a substance
without changing its composition.
Examples of physical
changes:
 Cutting
 Braking
 Phase Change=transition of
mater from one state to another.
Chemical changes vs.
physical changes
Physical Changes
 Alters a substance without
Chemical Changes
 Alters a substance by
changing its composition
(arrangement of its atoms)
changing its composition
(arrangement of its atoms)
 Does NOT change the

arrangement of atoms
DOES change the
arrangement of atoms
 SAME substance!
 NEW substance made!
Chemical/Physical changes
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