Transcript Document

Section
2-1 & 2-2
“Chemistry”
(Atoms & Water)
Yes, we’re jumping around to chapters
out of order – be okay with it :)
Write everything that is
underlined
2.1 Atoms, Ions, and Molecules / 2.2 Water
State Standards
• The fundamental life processes of plants and animals
depend on a variety of chemical reactions that occur
in specialized areas of the organism's cells. As a
basis for understanding this concept.
• Scientific progress is made by asking meaningful
questions and conducting careful investigations. As
a basis for understanding this concept and
addressing the content in the other four strands,
students should develop their own questions and
perform investigations
2.1 Atoms, Ions, and Molecules / 2.2 Water
Section 2-1 KEY CONCEPT
All living things are based on
atoms and their interactions.
2.1 Atoms, Ions, and Molecules / 2.2 Water
What’s an atom you ask?
• An atom is the smallest basic
unit of matter
• An element is one type of atom
Hydrogen atom (H)
H
Oxygen atom (O)
O
2.1 Atoms, Ions, and Molecules / 2.2 Water
• An atom has a nucleus and electrons.
– The nucleus has protons and neutrons
– Electrons are in energy levels outside
nucleus
Oxygen atom (O)
Nucleus:
8 protons (p+)
8 neutrons (n0)
outermost
energy level:
6 electrons (e-)
inner energy level:
2 electrons (e-)
2.1 Atoms, Ions, and Molecules / 2.2 Water
• A compound is made of atoms of
different elements bonded together.
–Examples:
–water (H2O)
–Salt (NaCL)
_
H
+
O
H
+
2.1 Atoms, Ions, and Molecules / 2.2 Water
–carbon dioxide (CO2)
Carbon (C)
Oxygen (O)
Oxygen (O)
2.1 Atoms, Ions, and Molecules / 2.2 Water
• An ion is an atom that has
gained or lost one or more
electrons.
–positive ions (+)
–negative ions (-)
2.1 Atoms, Ions, and Molecules / 2.2 Water
• Ionic bonds form between
oppositely charged ions.
Na loses an
electron to
CI
Sodium
atom (Na)
Chlorine
atom (CI)
gained
electron
ionic bond
Sodium
ion (Na+)
Chloride
ion (CI-)
2.1 Atoms, Ions, and Molecules / 2.2 Water
• A covalent bond forms when atoms share a
pair of electrons. covalent
bonds
Oxygen
atom (O)
Carbon
atom (C)
Oxygen
atom (O)
Carbon dioxide (CO2 )
2.1 Atoms, Ions, and Molecules / 2.2 Water
Section 2-2 KEY CONCEPT:
Water’s unique properties
allow life to exist on Earth
2.1 Atoms, Ions, and Molecules / 2.2 Water
Life depends on hydrogen bonds in water.
• Water is a polar molecule
– Polar molecules have slightly charged
regions
_
O
H
+
H
+
– Nonpolar molecules do not have charged
regions
2.1 Atoms, Ions, and Molecules / 2.2 Water
_
O
H
H
+
+
H
H
+
+
H
+
O
_
O
_
H
+
_
+
H
+
H
O
H
O
_
H
+
_
Hydrogen bonds
form between
slightly positive
hydrogen atoms
and slightly
negative atoms
(opposite
charges attract)
2.1 Atoms, Ions, and Molecules / 2.2 Water
• Hydrogen bonds are responsible for three
important properties of water.
–high specific heat
–cohesion
–adhesion
2.1 Atoms, Ions, and Molecules / 2.2 Water
Many compounds dissolve in water
• A solution is formed when one substance
dissolves in another.
– A solution is a homogeneous mixture.
– Solvents dissolve other substances.
– Solutes dissolve in a solvent.
solution
2.1 Atoms, Ions, and Molecules / 2.2 Water
Some compounds form acids or bases.
• An acid releases a hydrogen ion when it
dissolves in water.
–pH less than 7
stomach acid pH between 1 and 3
more acidic
2.1 Atoms, Ions, and Molecules / 2.2 Water
• A base removes hydrogen ions from a
solution.
–pH greater than 7
bile pH between 8 and 9
more basic
2.1 Atoms, Ions, and Molecules / 2.2 Water
• A neutral solution has a pH of 7
pure water pH 7
2.1 Atoms, Ions, and Molecules / 2.2 Water
So Why is Water SOOOO Important to Life on Earth???
• Water resists change in temperature; this is
important in cellular function
• Many compounds dissolve in water- sugar and
oxygen can’t be transported unless they are
dissolved in water based fluids
• Water has a neutral pH of 7