2.1 the nature of matter · 2013-09-22 · 2. water molecules form hydrogen bonds o hydrogen bonds...
TRANSCRIPT
2.1 The Nature of Matter
Atoms = basic unit of matter
O Protons and neutrons
O Protons have positive charge
O Neutrons have NO charge
O Both found in the nucleus of an atom
O Electrons
O Negatively charged
O Much smaller than protons and neutrons
O In constant motion around the nucleus
O Valence electrons important for bonding with other atoms
Atoms are neutral when they have equal numbers of protons and
electrons. The charges balance each other out.
An atom of carbon
O How many protons?
O How many electrons?
O How many neutrons?
O Is the atom neutral?
Your turn… Draw an atom of helium with 2 protons, 2 electrons and 2 neutrons
Elements and Isotopes
O Element = pure substance that consists entirely of
one type of atom
O Period table shows elements arranged by atomic
number
O Atomic number = number of protons
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Elements and Isotopes
O Isotopes = Can you figure it out based on the
information below???
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How are the isotopes of carbon similar? Different?
Elements and Isotopes
O Isotopes = atoms of the same element with different
number of neutrons
O Proton number is the same
O Electron number is the same
O Identified by mass number (total number of protons and
neutrons)
O Isotopes have same chemical properties
Slide 2 of 3
Your turn… How many protons and neutrons are in the nucleus of the isotope helium-5? How many electrons do helium and helium-5 have?
Elements and Isotopes
O Radiocative Isotopes = nuclei are unstable and break
down at a constant rate
O Used to determine age of rock and fossils
O Used to detect and treat cancer
O Kill bacteria that cause food to spoil
O Used as markers or tracers to follow the movement of
substances within organisms
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Chemical Compounds
O Substances formed by the chemical combination of 2
or more elements in definite proportions
O Physical and chemical properties are different than the
starting elements
Chemical Bonds
1. Ionic Bonds – electrons are transferred from one atom
to another
O An atom that loses an electron = + ion
O An atom that gains an electron = - ion
O Example : NaCl
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Chemical Bonds
2. Covalent Bonds – electrons are transferred from one
atom to another
O Stronger than ionic bonds
O Common in the material that makes up living things
O Ex: water
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Chemical Bonds
3. Van der Waals forces – intermolecular forces of
attraction between oppositely charged regions of nearby
molecules
O By themselves, not as strong as ionic or covalent bonds
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2.2 Water
1. Water is a polar molecule.
O Uneven distribution or sharing of electrons between
oxygen and hydrogen atoms
O Oxygen = negative pole
O Hydrogen = positive pole
2. Water molecules form hydrogen bonds
O Hydrogen bonds form between the oxygen (-) of one
water molecule and the hydrogen (+) of another water
molecule because opposite charges attract
O Hydrogen bonds can explain the properties of water
O Water expands when freezing = ice less dense than liquid
O Water can dissolve many other substances
O Cohesion
O Adhesion
O Heat capacity – water can absorb a lot of heat energy
3. Water is a universal solvent.
O When an ionic compound such as sodium chloride is
placed in water, water molecules surround and
separate the positive Na ions and negative Cl ions,
dissolving the solid
Dissolving
animation
Acids, Bases and pH
O Why is it important for cells to buffer solutions against rapid changes in pH?
O pH = measure of H+ ions
O Acids have a higher H+ concentration
O Bases have a lower H+ concentration
O pH decreases as H+ concentration increase
O Acids have a low pH (1-6)
O Bases have a high pH (8-14)
O Pure water (neutral) has pH of 7
Quick Lab – determining pH of household items
1. Predict whether the food samples provided
are acidic or basic
2. Test pH of each item with universal
indicator
O Use the scale provided by your teacher to
determine the pH
3. Construct a pH scale (1-14) and write each
item you tested in the appropriate place on
the pH scale
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The importance of buffers
O Acids form H+ in solution, have high H+ concentration
and have pH less than 7
O Bases forms OH- in solution, have low H+
concentration and have pH greater than 7
O Buffers control pH in living things (maintain
homeostasis)
O Weak acids or bases that can react with strong acids and
bases to prevent sharp sudden changes in pH
O Ex: bicarbonate and phosphate ions
Closure
O Use the pH scale pictured
to rank the following
items in order of
increasing acidity: soap,
lemon juice, milk and
acid rain
2.3 Carbon Compounds
The Chemistry of Carbon
O Four valence electrons (available for bond formation)
O Carbon can bind with other elements (H, O, N, S, P)
O Carbon can bind with other carbons
O Can be single, double or triple bonds
O Carbon chains can be unlimited in length
O Carbon chains can form rings
Macromolecules
O “giant molecules”; “organic compounds”
O Formed by polymerization reactions (a.k.a. dehydration
synthesis)
O Small subunits = monomer
O Many monomers linked together = polymer
O Four groups of macromolecules based on
chemical composition
1. Carbohydrates
O Elements: C, H and O with 2:1 H:O ratio
O Functions:
O Main source of energy
O Also used for structural support (plant cells)
O Other Info:
O Monomer = simple sugars (monosaccharides and
disaccharides; glucose, sucrose)
O Complex sugars (polysaccharides)
O Excess sugar stored as glycogen in animal cells
O Excess sugar stored as starch in plant cells
O Cellulose = plant polysaccharide give support to cell wall
2. Lipids
O Elements: C, H and O with NO 2:1 H:O ratio Functions:
O Long-term energy storage
O Cell membranes
O Waterproof coverings (bird feathers)
O Hormones (chemical messengers)
O Other Info:
O large hydrocarbon chains
O Not soluble in water (hydrophobic)
O Made up of glycerol and fatty acids
2. Lipids cont’d
O Saturated fatty acids – all single bonds in HC chain
O Unsaturated – presence of double bonds in HC chain
Comparing Fatty Acids
O Which of the four fatty acids is saturated?
O Which of the fatty acids are unsaturated?
O How does melting point change as the # of carbon-carbon double
bonds increases?
O Which fatty acid is solid at room temperature?
O Which is liquid at room temperature?
3. Nucleic Acids
O Elements: C, H and O, N and P
O Functions:
O Store and transmit hereditary or genetic information
O Other info:
O Monomer = nucleotide
O 2 kinds of nucleic acids = DNA and RNA
4. Proteins
O Elements: C, H and O and N
O Functions:
O Control reaction rates
O Regulate cell processes
O Transport of substances around the body
O Help fight disease
O Other Info:
O Monomer = amino acid
O All amino acids have similar structure (central carbon,
amino group and carboxyl group) but differ in side chain
ENERGY
4. Proteins continued
O Other Info:
O Protein structure – 4 levels of folding
O Primary structure = sequence of amino acids
O Secondary structure = folding or coiling of amino acid chain
O Tertiary structure = complete 3D arrangement of protein
chain
O Quarternary structure = multiple protein chains interact
O Protein shape is CRUCIAL for protein function
O Shape maintained by ionic and covalent bonds as well as
hydrogen bonds
