Transcript NAC_Ch2_Sec1.ppt

CHAPTER 2
Matter
and Atoms
2.1 Matter and the
Elements
What are things made of?
How many different kinds of substances can you identify?
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2.1 Matter and the Elements
What are things made of?
The “stuff” that we are made of is called matter.
Chemistry tells us how one kind of matter can be changed
into a completely different kind of matter.
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2.1 Matter and the Elements
Corn oil is a pure
substance
substance: a kind of matter that can’t be separated into
other substances by physical means such as heating,
cooling, filtering, drying, sorting, or dissolving.
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2.1 Matter and the Elements
Oil and vinegar
dressing is
a mixture of
substances
Corn oil is a pure
substance
mixture: matter that contains more than one substance.
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2.1 Matter and the Elements
Is “pure orange juice”
a pure substance?
“Pure orange juice”
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Water
Flavoring chemicals
Citric acid
Sugars
Fruit pulp
…
2.1 Matter and the Elements
Look at your desk – What is it made of?
wood, metal…
Can you think of a few physical properties?
is it heavy?
is it bendable?
does it feel cold?
can you scratch it?
…
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2.1 Matter and the Elements
Physical properties
Examples:
Mass
Density
Color
Physical properties can
be measured or seen
through direct observations.
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2.1 Matter and the Elements
Physical changes include changes
in shape, phase or temperature.
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2.1 Matter and the Elements
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2.1 Matter and the Elements
Chemical properties
are observed when
a substance changes into
a different substance.
Chemical change
Iron
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Rust
2.1 Matter and the Elements
Signs
that a
chemical
change
has occurred
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2.1 Matter and the Elements
Macroscopic and microscopic scales
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2.1 Matter and the Elements
element: a substance that cannot be separated into
simpler substances by chemical means.
Each element is a unique type of atom.
All oxygen atoms
are identical.
An oxygen atom is different
from a silicon atom or
a potassium atom.
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2.1 Matter and the Elements
How small is an atom?
1 grain of rice = 0.01 gram
1 hydrogen atom = 1.678 x 10–24 grams
= 0.000000000000000000000001678 grams
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2.1 Matter and the Elements
How would you organize
all those elements?
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2.1 Matter and the Elements
The periodic table
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2.1 Matter and the Elements
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2.1 Matter and the Elements
The periodic table organizes elements according to how they
combine with other elements (based on their chemical properties).
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2.1 Matter and the Elements
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2.1 Matter and the Elements
Increasing atomic number
Increasing atomic number
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2.1 Matter and the Elements
Increasing atomic number
Increasing atomic number
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Hydrogen
Lightest element
Atomic number: 1
Uranium
Heaviest naturally occurring element
Atomic number: 92
2.1 Matter and the Elements
Elements that belong to the same group (column)
have similar chemical properties.
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2.1 Matter and the Elements
Reminder
1 atomic mass unit (amu) = 1.66 x 10-24 g
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2.1 Matter and the Elements
The atomic mass is
the mass of:
1) a single atom in amu.
2) a mole of atoms in grams.
What does
that mean?
One single hydrogen atom weighs 1.01 amu.
One mole of hydrogen atoms weighs 1.01 g.
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2.1 Matter and the Elements
The atomic mass is
the mass of:
1) a single atom in amu.
2) a mole of atoms in grams.
What does
that mean?
One single carbon atom weighs 12.0 amu.
One mole of carbon atoms weighs 12.0 g.
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2.1 Matter and the Elements
Avogadro’s number
One mole contains
6.02 x 1023 atoms
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2.1 Matter and the Elements
How many moles are in 100 g of sulfur (S)?
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2.1 Matter and the Elements
How many moles are in 100 g of sulfur (S)?
Asked:
Given:
Relationships:
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The number of moles
The element is sulfur and there are 100 g
One mole of sulfur has a mass of 32.065 g
2.1 Matter and the Elements
How many moles are in 100 g of sulfur (S)?
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Asked:
Given:
Relationships:
The number of moles
The element is sulfur and there are 100 g
One mole of sulfur has a mass of 32.065 g
Solve:
 1 mole S 
100 g S  
  3.12 moles S
32.065
g
S


Answer:
100 g of sulfur contains 3.12 moles of sulfur atoms.
2.1 Matter and the Elements
How many grams of calcium (Ca) do you need
to have 2.50 moles of calcium?
Asked:
Given:
Relationships:
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The number of grams
The element is calcium and there are 2.50 moles
One mole of calcium has a mass of 40.078 g
2.1 Matter and the Elements
How many grams of calcium (Ca) do you need
to have 2.50 moles of calcium?
Asked:
Given:
Relationships:
The number of grams
The element is calcium and there are 2.50 moles
One mole of calcium has a mass of 40.078 g
Solve:
 40.078 g Ca 
2.50 moles Ca  
  100.2 g Ca
 1 mole Ca 
2.50 moles of calcium has a mass of 100. g.
Answer:
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2.1 Matter and the Elements
Physical properties can be seen
and measured
Chemical properties are observed
when one substance is changed into
another
Elements are
organized in
a periodic table
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This allows to convert
grams to moles and vice versa.
2.1 Matter and the Elements
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