10/6 - Q of D
- Chemistry
Why do we study chemistry in biology class?
After you finish your answer please go to the
side counter and pick up the notes for this
chapter.
Why do we study chemistry in biology class?
– Chemistry explains how and why chemicals
interact with each other
– Cells are composed of chemicals, elements
and molecules
– To understand how cells work you must have a
basic understanding of chemistry
Chapter 2
Chemistry
Please get 3 (different) colored
pencils or crayons from side counter.
Chemistry is divided into 2 branches
– Inorganic
Small simple substances
Basic molecules of life
Nonliving substances
Examples: oxygen, water, salt
– Organic
Larger and more complex
Come from living organisms
Contain Carbon (except: )
Examples: carbohydrates, fats, proteins
Chemistry Basics
Atoms are the building blocks of the
universe; everything is made of atoms
Atoms from a Greek word that means
“unable to cut”
Keystone Definition:
ATOM – the smallest unit of an
element that retains the chemical and
physical properties of that element.
Atoms are made of smaller units called
subatomic particles
Protons – are small, positively charged
particles found in nucleus
Neutrons – are neutrally charged
particles, in nucleus
Electrons – negatively charged
particles, found orbiting around the
nucleus in electron shells/energy levels
The atomic number tells the # of protons and
# of electrons
The atomic mass number tells the # of
protons + the # of neutrons
Normally the number of protons is equal to
the number of electrons making the atom
electrically neutral or stable.
Elements
The simplest substances on earth
Made from only one type of atom
92 naturally occurring elements
Each has different properties and
characteristics that make it unique (solid,
liquid, gas, helpful, flammable, poisonous
etc.)
Biological Elements
There are 4 major elements for life –
– Carbon (C),
– Hydrogen (H),
– Oxygen (O) and
– Nitrogen (N).
These are called the BIG 4 elements
They make up 96% of all organisms on
earth
Minor Elements
Phosphorus (P)
Magnesium (Mg)
Potassium (K)
Calcium (Ca)
Sodium (Na)
Sulfur (S)
Chlorine (Cl)
Low percentages in the body – about 2.5%
of the body is made of these elements.
They are important for body functions.
Trace Elements
Boron (B)
Fluorine (F) Iodine (I) Selenium (Se)
Zinc (Zn)
Chromium (Cr)
Iron (Fe)
Manganese(Mn) Cobalt (Co)
Silicon (Si)
Copper (Cu)
Molybdenum (Mo)
Very low percentages in the body (about 1%) but
are very important for the body processes
We get all our needed elements (vitamins) through
our food or supplements.
Isotopes
Sometimes the number of neutrons in an
element can change when everything else
stays the same.
Atoms of the same element that differ in the
number of neutrons they contain are called
isotopes.
Some isotopes are radioactive and can be
very useful for scientists – called
radioisotopes.
Ex: Carbon 12 is normal carbon has 6p, 6e,
and 6 n. Carbon 14 is a radioisotope and
has 6p, 6e, and 8n. It is used for carbon
dating artifacts.
Other uses include medical tests, drug tests,
radiation for cancer treatments, diagnosing
diseases, tracing pathways in an organism,
and sterilizing food.
Common isotopes used are Fe, Na, Co and I
Putting Elements Together
A compound is 2 or more elements
chemically bonded together in a definite
proportion
Chemical or molecular formula shows the
numbers of atoms of each element in the
compound Example: H2O CH4 C6H12O6
A structural formula shows how the atoms
are bonded together. Example:
There are 2 major types of bonds
1. Ionic bonds
Formed when atoms gain or lose electrons
An atom with extra electrons in its valence shell
will transfer them to an atom that needs
electrons in its valence shell.
This causes a positive ion and a negative ion
The opposites attract and the atoms are held
together.
Examples: NaCl
2. Covalent bonds
Formed when atoms share electrons
– 1 pair of e- are shared = single bond
– 2 pairs of e- shared = double bond
– 3 pairs of e- shared = triple bond
More common in many of the substances
found in organisms
Are very strong bonds
Examples: sugar, fats, propane
NaCl
KF
CH4
NH3
Acids
Substances that have more H+ ions
Taste sour
Between 0-7 on the pH scale
Examples of acids would be lemon juice,
stomach acid, coffee, tomatoes, saliva
Bases
Substances that have more OH- ions
Taste bitter
Between 7-14 on the pH scale
Examples of bases would be saltwater,
soap, bleach, cleaners
pH
Measure of acidity is pH.
Scale from 0-14
Water is a pure substance – only made
from Hydrogen and Oxygen so it is neutral
or 7 on the scale.
It is important that the body maintain the
proper pH in order for reactions to occur.
Most reactions in humans occur at pH of
7.4 (slightly basic)
You can die if your overall body pH goes
lower than 7 or higher than 7.8
Your body has buffering systems in place
to maintain this pH (homeostasis)
WATER
¾ of the earth’s surface
70% of the human body.
Most chemical reactions in the body take
place in water
Only common substance on earth to exist
in all 3 physical forms – gas, liquid, solid.
Vital for life as we know it
Properties of Water
Water is a polar molecule. This means that
it has an unequal distribution of charge on
different sides of the molecule.
Because it is polar, water is the universal
solvent. Can dissolve many substances.
Important because many substances in
our bodies must be dissolved in water for
reactions to occur.
Water molecules are attracted to each
other and form hydrogen bonds between
them.
Water has cohesion – means that water
molecules stick to each other. This
produces surface tension. Water acts as if
it has a “thin skin”
Water has adhesion – water molecules
stick to other types of molecules
Water displays capillary action (capillarity) –
can move upward through small tubes
against gravity.
Plants use cohesion,
adhesion and capillarity to
move water from roots to
leaves.
Water has a high specific heat. This
means that water resists temperature
changes – takes a lot of heat/energy to
raise the temperature.
This helps to keep the temperatures on
Earth stable and allows organisms to
remain at stable temperatures even when
environment changes
This also helps animals cool off by
sweating, panting and bathing.
Solid water is LESS dense than liquid
water….this is not what most liquids do!
Water has it greatest density at 4oC – this
means that water expands when it freezes
and ice floats.
Important for water habitats. Helps to
insulate the water below the ice so that
aquatic creatures can survive.
ACID RAIN
Precipitation is naturally slightly acidic due
to reactions with carbon dioxide in the
atmosphere.
The term acid rain describes precipitation
that has a pH lower than 5.5. It can be
acid rain, snow or fog.
What causes acid rain?
Burning of fossil fuels (coal) releases
pollutants including sulfur dioxide and
nitrogen oxide.
These pollutants react with water droplets
in the upper atmosphere and make sulfuric
acid and nitric acid.
These acids then fall to the ground in
rain/snow
Effects of Acid Rain
1. Water ecosystems are disturbed
– Makes rivers, lakes more acidic
– Water organisms begin to die or have their life
cycles disrupted
Organisms
Preferred pH range
Aquatic plants (algae)
6.5 to 12.5
Carp, catfish, some insects
6 to 9.5
Bluegill
6.5 to 9.5
Snails
7 to 10
Stonefly and caddisfly larvae
7 to 8.5
One of the things that can be done to help
correct the pH of water and soil is to add
limestone. This acts as a buffer and helps
to neutralize the acids.
In some areas limestone is added to lakes
and streams to help prevent the organisms
from dying.
2. Harms vegetation
– Damages leaves of plants
– disrupts the way that plants take in and
release water, carbon dioxide and oxygen,
– disrupts the amount of food the plant can
make through photosynthesis
– decreases the amount of food we can harvest
3. Deteriorates buildings and historical
monuments
– Acid “eats” away at
the structures
4. Damage human
health
– Causes more lead
to be released
from water pipes
– Still unknown
effects
5. Financial Impact
– Estimated that
effects of acid rain
cause 5 billion
dollars of damage a
year in the eastern
US.
The greatest Acid Rain problems are in…
– Mid Atlantic States (Ohio, New York, PA)
–WESTERN PENNSYLVANIA!
WHY?????
– Almost half of all emissions in the US
are from big industrial cities in Indiana,
Illinois, Michigan, Ohio and Missouri
– Winds carry these gases in a northeast
direction
How bad is the problem?
The average pH of Pennsylvania rainfall is
between 4.1 and 4.3
Pennsylvania receives one of the highest
concentrations of acid precipitation in the
US and the world.
What is helping in PA
In PA we have a lot of limestone. This is a
natural way for the acid rain to be buffered
before entering the lakes, streams.
This lessens the impact of acid rain in this
area and prevents us from seeing the
most severe effects of the precipitation.
Other areas do not have this natural
limestone and have seen the full effects.
What is being done?
The Clean Air Acts of the 1990’s require a
reduction in the amount of pollutants from
industry. This acts are still being
implemented in phases.
Conservation is stressed – conserve
electricity to reduce the amount of coal
burned. Use cars less to reduce pollution
Is it working?
The measures are working – the pH is
making slow changes – moving a little
towards neutral.
Has been a 22% reduction in the amount
of sulfur dioxide released from power
plants.
As more measures are enforced expected
to keep getting better.
Ways you can help
Use less fossil fuels
– Reduce pollution by using your car less.
– Conserve electricity in your house
– Turn off/unplug appliances when not in use
– Reduce heating/cooling of home
– Buy local products
– Use alternative energy sources if possible
The END
of chapter 2 !
Assignment:
Pg 47 # 1-3,5,7, and short
response