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Chemistry: Unit 2-The nature of matter Notes.
NOTES (2-1) NATURE OF MATTER
The study of chemistry begins with the Atoms-Atoms are the basic unit of matter.
Atom means too small “unable to be cut” this was referring to “matter”.
The subatomic particles that make up an atom are protons, neutrons and
electrons.
Protons have a positive charge and are located inside the nucleus.
Neutrons have no charge and are located inside the nucleus.
Electrons have a negative charge and are located outside the nucleus in rings or
shells.
Electrons are in constant motion in the space surrounding the nucleus.
Atoms have equal number or protons and electrons; therefore their charge is
neutral.
Electrons create special bonds with other electrons through its outer most shell
where these electrons are called “valence”. Valence electrons bond with other
valence electrons of other elements and form compounds.
Atoms are the central component of elements.
Elements are a pure substance that consists of one type of atom. There are over
110 elements on the periodic chart.
Atoms of the same element that differ in the number of neutrons they contain are
called isotopes. Common Isotopes are found in Carbon and Uranium.
Ex: C12
C13
C14
Shown are the different numbers that can exist for each carbon. The number of
neutrons in the nucleus differs for each element, hence the 12, 13 and 14 atomic
mass number. Any element that has a different numbers of neutrons but the same
number of protons and electrons remain as that element on the periodic table is
called an isotope.
A chemical compound is a substance formed by the chemical combination of two
or more elements in definite proportions.
Each compound has a chemical formula with a capital letter that represents the
name of the elements and a possible subscript, which tells the number of atoms of
that element.
Two main types of bonds that can take place between the valence electrons, they
are covalent and ionic bonding. Both deal with the type of connections that exists
between the valence electrons and whether these share their electrons or give up or
take these electrons to bond.
If the outer most electrons share, covalent, than usually they include a bond with
hydrogen or carbon and they becomes a molecule.
If the outer most electrons of one element steal or give up an electron to the other
element then that compound becomes ionic. Ionic bonds cause the neutral charge
to change to either positive or negative based on the new relationship between the
positive protons or negative electrons.
Ck: What information is contained in a chemical formula?
Answer: The types of elements that exist in the compound and the number of atoms
of each element in that compound.
NOTES (2-2) PROPERTIES OF WATER
Cohesion properties exist between attractions of molecules of the same substance.
Water molecules are an example of the elements of water sticking to elements of
other water molecules.
Adhesion properties exist between attractions of unlike substances. Ex: water
molecules and the glass that holds the water.
Water molecules are neutral. The positive charges on its 10 protons balance out the
negative charges on its 10 electrons.
However the polarity of a water molecule along its chain of protons and electrons
might vary at a particular side of the chain therefore one side has more of a positive
end and the other side a negative side.
Water molecules are polar because there is an uneven distribution of electrons
between the oxygen and the hydrogen atoms. The negative pole is nearest the
oxygen and the positive pole is between the hydrogen’s.
Water’s cohesion causes molecules on the surface of water to be drawn inward,
which is why drops of water form beads on a smooth surface.
Cohesion explains why some insects and spiders can walk on a pond’s surface.
Adhesion is an attraction between molecules of different substances.
Why does the water in a graduated cylinder dip slightly in the center because the
adhesion between water molecules and glass molecules is stronger than the
cohesion between water molecules?
Water is not always pure- it is found as part of a mixture. A mixture is a material
composed of two or more elements or compounds that are physically mixed
together but not chemically combined. If you stir salt and pepper together they mix
but still are salt and pepper, they retain their properties.
Two types of mixtures that can be made with water are solutions and suspensions.
Solutions have evenly distributed components. (Solute and Solvent). This is not
to say that you have even amount of the solute and of the solvent. Solutions have
less solute (particle dissolving) and more solvent (substance in which the
solute dissolves). Once you mix the components you can’t see the different
components that have combined.
Suspensions: Materials that do not dissolve when place in a solvent (water), but
separate into pieces so small that they do not settle out.
Blood is a solvent in your body. Cells can act as suspensions in the blood as the
blood moves throughout the body.
Acids:
Have a high concentration of H+ ions than pure water therefore there pH values is
less than 7. The lower the basic number the higher the presence of Hydrogen ions.
Strong values are usually 0-3; weak acids are 5-6.
Bases:
A base is a compound that produces hydroxide ions (OH-) in a solution.
Basic is also known as alkaline solutions. The greater the numbers of hydroxide
ions the higher the pH number greater than 7. Strong bases are high at 14; weak
base is 8-9.
Buffers:
Controlling pH in the body is essential for proper functioning if homeostasis is not
maintained the chemical reactions that do not take place will cause damage to cells;
processes will not take place or may not work at the correct time. These are
controlled by pH which is kept between 6.5—7.5. When the body controls this it is
through the use of buffers. Buffers are weak bases or acids that can react with
strong acids or bases to prevent sharp or sudden changes in pH.
(2-3) Carbon Compounds:
The chemistry of Carbon:
-4 places to bond at 4 valence electrons
-ability to form chains (unlimited length)
-bonds with many elements
-likes to bond with carbon, hydrogen, oxygen, phosphorus, sulfur and nitrogen.
-can form single, double, and triple bonds and can form rings. Can form millions of
different large and complex structures.
Macromolecules:
These are giant molecules, large living cells made from thousands of smaller
molecules. Formed by a process known as polymerization, this is where large
compounds are built by joining smaller units together these smaller sub units are
called monomers.
There are four groups of organic compounds found in living things; carbohydrates,
lipids, nucleic acids and proteins.
Carbohydrates:
-Are compounds made up of carbon, hydrogen and oxygen.
-The ratio is 1:2:1.
-Used as a main source of energy.
-Plants and animals use carbohydrates for structural purposes.
-Carbohydrates break down as sugar or glucose, which is immediate energy
available for cell activities.
-Complex carbs are known as starch.
-Simple sugars are known as monosaccharides.
-Monosaccharides include galactose component of milk and fructose sugar in fruit.
-Polysaccharides are many monosaccharides.
-Animals store extra sugar in a polysaccharide called glycogen (animal starch).
-Plants store extra sugar in a polysaccharide called cellulose (give plants their
rigidity and strength). Cellulose is major component of wood and paper.
Lipids: Not soluble in water.
-Are compounds made up of carbon, hydrogen and oxygen.
-The ratio is 1:3:1 or greater than 1>3:1.
-Used to store energy.
-Important as parts of biological membranes and act as a waterproof covering.
-Also are steroids. Steroids can serve as chemical messengers.
-Examples; fats, oils and waxes.
-Lipids are formed when a glycerol molecule combines with compounds called fatty
acids.
-There are saturated bonds if each carbon atom is joined to another carbon atom by
a single bond. Saturated because the fatty acids contain the maximum possible
number of hydrogen atoms.
-If there is at least one carbon-carbon double bond in a fatty acid, the fatty acid is
said to be unsaturated.
-If the fatty acid contains more than one double bond it is polyunsaturated.
Unsaturated acids are liquid at room temp.
-Examples of polyunsaturated fatty acids are canola, peanut oil, sesame oil and corn
oil.
Nucleic Acids:
-Macromolecules containing Carbon, Hydrogen, Oxygen, Nitrogen and Phosphorus.
-These are polymers assembled from monomers known as nucleotides.
-Nucleotides contain 3 parts; nitrogen base, phosphate and a 5 carbon sugar in DNA.
-These nucleotides join together to make nucleic acids.
-Nucleic acids store and transmit hereditary genetic information.
-Two types of nucleic acids;
Deoxyribose (sugar) nucleic acid (DNA)
Ribose (sugar) nucleic Acid (RNA).
Proteins:
-These are macromolecules that contain Carbon, Hydrogen, Oxygen and Nitrogen.
-Polymers of molecules called Amino Acids.
-These have an amino group (NH2) on one end and a carboxyl group (COOH) on the
other end.
-More than 20 different amino acids are found in nature.
-All amino acids are identical in the regions where they may be joined to by covalent
bonds.
-Amino acid joins to any other amino acid by bonding an amino group to a carboxyl
group.
-The portion of each amino acid that is different is a side chain called an R-group.
-Some R-groups are acidic and some are basic.
-Some R-groups are polar and some are non-polar.
-Some contain carbon rings.
-The instructions for arranging amino acids into many different proteins are stored
in DNA.
-EACH SPECIFIC PROTEIN HAS A SPECIFIC ROLE.
-Some control the rate of reactions and regulate cell processes.
-Some are used to form bones and muscles.
-Some transport substances into or out of cells, or help to fight disease.
-Proteins have 4 levels of organization:
1. Sequence of amino acid in a protein chain.
2. Amino acids within a chain can be twisted or folded.
3. Amino acid is folded.
4. Each chain has a specific arrangement in space
(2-4) Chemical Reactions and Enzymes.
Everything that happens in an organism; its growth, in its interaction with the
environment, reproduction, movement are all based on chemical reactions.
A chemical reaction is a process that changes one set of chemicals into another set of
chemicals.
Reactions can occur fast or slow.
The elements or compounds that enter into a chemical reaction are known as
chemical reactants.
The elements or compounds produced by a chemical reaction are known as
products.
Chemical reactions always involve the breaking of bonds in reactants and the
formation of new bonds in products.
Ex: CO2 + H20 arrow H2CO3
Carbon dioxide reacts with water to produce a highly soluble compound called
carbonic acid. (H2CO3)
This reaction enables the bloodstream to carry carbon dioxide to the lungs. In the
lungs, the reaction is reversed.
H2CO3 arrow CO2 + H20
This reverse reaction produces carbon dioxide gas, which is released as you exhale.
Energy in Reactions:
Energy is released or absorbed whenever chemical bonds form or are broken.
Because chemical reactions involve breaking and forming bonds, they involve
changes in energy.
Energy Changes:
Energy changes are one of the most important factors in determining whether a
chemical reaction will occur.
Some reactions release energy, some absorb energy. Those that release energy
occur spontaneously, those that absorb need a source of energy.
Every organism must have a source of energy to carry out chemical reactions.
Plants get their energy from trapping and storing sunlight in compounds.
Animals get their energy from consuming plant and animals.
Humans release their energy from the chemical reactions that occur when humans
metabolize or break down digested food.
Activation Energy:
This is the energy that is needed to get a reaction started. It is the factor in whether
the overall chemical reaction releases energy or absorbs energy.
Enzymes:
-Enzymes are proteins that act as biological catalysts.
-Enzymes speed up chemical reactions that take place in cells.
-Enzymes act by lowering the activation energy. Lowering the activation energy has
a dramatic effect on how quickly the reaction is completed.
-Enzymes are specific, they catalyzes only one chemical reaction. For this reason
enzymes get its name from the reaction it catalyzes.
Enzyme action:
How do enzymes do their jobs? For a chemical reaction to take place, the reactants
must collide with enough energy so that existing bonds will be broken and new
bonds will be formed. If the reactants don’t have enough energy, they will be
unchanged after the collision.
Enzyme- substrate complex:
Enzymes provide a site where reactants can be brought together to react. This site
reduces the energy needed for reaction. The reactants of enzyme-catalyzed
reactions are known as substrates.
Substrates bind to a site on the enzyme called the active site. The active site and
the substrate site have precise shapes that match. This fit is so precise that this is
called lock and key fit. Once the reaction is over, the products of the reaction are
released and the enzyme is free to start the process over again.
Enzymes can be affected by any variable that influences a chemical reaction. These
include those that digest food, work best at certain pH values. Many enzymes are
affected by temperature close to 37 degrees Celsius= 98.6 F.
Cells regulate the activities of enzymes by containing proteins that regulate or turn
on or off enzymes. These enzymes play essential roles in regulating chemical
pathways, making materials that cells need, releasing energy and transferring
information.