Transcript Chapter 2 Matter and Change

Chapter 2
Matter and Change
Chemistry pg. 38
2.1 Properties of Matter
• Properties used to describe matter are classified
as:
1. Extensive – depends on the amount of
matter in a sample
ex. Mass, volume
2. Intensive – depends on the type of matter
in a sample, not the amount
ex. Color, hardness, boiling point
Substance
• Matter that has a uniform and definite
composition
ex. Gold, copper (pure substances)
Every sample has identical intensive properties
because every sample has the same
composition
Physical Property
• A quality or condition of a substance that can be
observed or measured without changing the
substance’s composition
• Help chemists identify substances
• Hardness
• Color
• Conductivity
• Malleability
(see Table 2.1, Pg. 40)
Three states of matter
• Solid-definite shape, volume, not easily
compressed
• Liquid-indefinite shape, flows, definite
volume, almost incompressible
• Gas-indefinite shape, indefinite volume, easily
compressed
• http://www.chem.purdue.edu/gchelp/liquids/
character.html
Physical Changes
• Properties of a material change but the
composition does not
ex. Boil, freeze, melt, condense
AND
break, split, grind, cut, crush
Physical changes can be
REVERSIBLE or IRREVERSIBLE
2.2 Mixtures
• Physical blend of 2 or more components
ex. Chicken noodle soup, air
Mixtures can be classified as…
HETEROGENOUS or HOMOGENOUS
(based on distribution of components)
Matter can be Heterogeneous
• The composition is not uniform
throughout
• More than one phase…so it’s a mixture
-Phase – any region with a uniform set
of properties that can be separated from
each other by definite boundaries called
interfaces
Matter can be
Homogeneous
• The composition is uniform
throughout, evenly
distributed
• Only one phase
Identify the following
• Concrete __________________________
• Vinegar____________________________
• Carbon dioxide_____________________
• Granite rock________________________
• Milk________________________________
Separating mixtures
• Distillation - a liquid is boiled to produce a
vapor which is condensed into a liquid
Other ways?
distillation
• How to perform simple distillation in the
chemistry lab | Wonder How To
2.3 Elements and Compounds
• Substances classified as
1. __________- simplest form of matter that
has a unique set of properties (O, H)
2. ___________- substance that contains 2 or
more elements chemically combined in a
fixed proportion (C6H12O6)
• Compounds can be broken down by
______________ means.
• Elements cannot be broken down
• Chemical change produces matter with a
different composition than the original
matter
Sugar
Carbon + Water
Properties of Compounds
• Generally, properties of compounds are
different from their component elements
• Sodium - soft, gray metal, reacts with oxygen
+
• Chlorine - yellow-green poisonous gas
Sodium chloride
Reaction
Distinguishing Substances and
Mixtures
• If the composition of a material is fixed, the
material is a substance
examples?
• If the composition of a material may vary, the
material is a mixture
examples?
Classifying Matter
• Classify the following materials as an element,
compound, or mixture.
a. Table salt
b. Salt water
c. Sodium
Symbols and Formulas
• Chemical symbols
O, C, Na, Ne
elements
• Chemical formulas
CO2 , H2O
compounds
2.4 Chemical Reactions
• Chemical Property – the ability of a substance
to undergo a specific chemical change
(describes the way a substance may react to
form other substances)
examples?
- can be observed only when a substance
undergoes a chemical change
• Fig. 2.13 (pg. 53)
Chemical reaction S + Fe
*physical - composition of matter never changes
*chemical – composition of matter always
changes
Chemical change = chemical reaction
Reactants
Products
• Chemical change = chemical reaction
(one or more substances change into one
or more new substances)
Reactants
Products
Recognizing Chemical Changes
4 Ways:
1. Color change
2. Formation of precipitate
3. Production of gas
4. Transfer of energy
• Precipitate
an insoluble substance that
forms in, and separates from, a
solution
Identify clues for chemical changes
magnesium ribbon in flame
Sodium iodide solution added to mercury(II)
chloride solution
Law of Conservation of Mass
• In any physical change or chemical reaction,
mass is __conserved______________.
mass of products = mass of reactants