Chemical Basis of Life - PowerPoint PPT Presentation

1 / 41
About This Presentation
Title:

Chemical Basis of Life

Description:

Chapter 4: Chemical Basis of Life ... – PowerPoint PPT presentation

Number of Views:178
Avg rating:3.0/5.0
Slides: 42
Provided by: Stude21250
Category:
Tags: acid | basis | chemical | life | salts

less

Transcript and Presenter's Notes

Title: Chemical Basis of Life


1
Chapter 4
  • Chemical Basis of Life

2
4.1 Elements of Life
  • Objectives
  • List the most common elements in living things
  • Compare and contrast elements and compounds
  • Vocab
  • Matter Element
  • Trace element Compound

3
4.1 Elements of Life
  • Matter anything that occupies space has mass
    (stuff)
  • Elements matter composed of only one type of
    atom pure substance cannot be broken down by
    chemical means.
  • Periodic Table Menu of elements

4
4.1 Elements of Life
  • Elements essential for life C H O N
  • Oxygen (65)
  • Carbon (18.5)
  • Hydrogen (9.5)
  • Nitrogen (3.3)
  • Trace Elements (Less than 0.01) - small amounts
    needed but important for proper function
  • Calcium, Phosphorous, Potassium, Sulfur, Sodium,
    Chlorine, Magnesium

5
An Element
  • Elements of the Periodic Table
  • They are represented by a one or two letter
    symbol on the periodic table.
  • Atomic protons
  • Atomic mass mass of nucleus (p n)

6
4.2 Atomic Structure
  • Structure

7
The Atom Basic unit of matterSubatomic Particles
  • Proton, Neutron Electron
  • 1. Proton () defines the atom)
  • 2. Neutron no charge
  • 3. Electron (-) almost no mass (so little we
    ignore it)
  • Electrons are not found in the nucleus
  • They travel at high speeds throughout the atom in
    a series of distinct energy levels that surround
    the nucleus.
  • Electron cloud Refers to all the possible
    locations that an electron could be.

8
Electron Cloud Model
9
Electron Energy Levels
  • Electrons orbit the nucleus at different
    distances, or Energy LEVELS.
  • Bigger distance more energy
  • 1st Energy Level fits 2 electrons (K)
  • 2nd Energy Level fits 8 electrons (L)
  • 3rd Energy Level fits 18 electrons (M) 8 act
    as valence
  • 4th Energy Level fits 32 electrons (N)

Note electrons do not really move in perfect
circles like this.
10
VALENCE ELECTRONS
  • Electrons in outer most energy level that are
    available for bonding.
  • Atoms want to have the MAX. of VALENCE
    ELECTRONS for stability.
  • valence determines chemical bonding
    reactivity.
  • If an atom already has the max of valence
    electrons, it wont form bonds

MAX. VALENCE 1st energy level 2 electrons 2nd
energy level 8 electrons 3rd energy level 8
electrons
11
What Is An Isotope?
  • The number of protons will never change, but the
    number of neutrons can vary from atom to the
    next.
  • Isotopes of an atom differ in neutron number.
  • ( Protons ? neutrons)

12
Radioisotopes
  • Some larger isotopes are unstable and decay
    giving off radiation (matter energy)
  • Such isotopes are useful in research and medicine
  • Biological spies for body scans
  • Radiation treatment for cancer

13
Radioactive Isotopes P.E.T. scan
http//www.riversideonline.com/source/images/image
_popup/c7_pet_alz.jpg
14
4.3 Chemical Compounds
  • Produced when elements combine to form substances
    consisting of two or more different atoms.
  • Represented by chemical formulas
  • Water (H2O), Table Salt (NaCl), Sulfuric Acid
    (H2SO4)

Multiple Molecules
Single Molecule
15
4.3 Forming Bonds Share or Transfer Electrons
  • In order to achieve stability an atom will
    either transfer or share electrons (valence)
  • This is achieved through either ionic or covalent
    bonding.
  • Watch http//www.youtube.com/watch?vQqjcCvzWwww
    featurerelated
  • http//www.youtube.com/watch?NR1vLRVW0tgSLRI

16
Ionic Bonding
  • Ionic bonding involves the transfer of
    electrons from one atom to another (gain or
    lose).
  • Ex NaCl
  • THIS IS HOW SALTS ARE MADE.

17
Covalent Bonding in Molecules
  • chemical bond formed by the sharing of electrons.
  • No elements are gaining or losing atoms.
  • Ex. H20

1 covalent bond 1 pair of shared valence
electrons
Structural formula model
Space filling model
18
Covalent Bonding Single Bond
  • Every shared valence electron forms a covalent
    bond holding the molecule together.
  • Single Bond (Share 1 pair v.e.)

19
Covalent Bonding Double Triple Bonds
  • Double Bond (Share 2 pair v.e.)
  • Triple Bond (Share 3 pair v.e.)

20
  • Bonding Prompt
  • The number of bonds that an atom can form depends
    on the atoms valence electrons (Remember 2, 8,
    8).
  • Keeping this in mind, identify the maximum number
    of bonds that can be formed by each of the
    following elements
  • a). H b). C c). O d). N e).
    He
  • B. Long complex molecules would probably be made
    up of _________ atoms. (Based on answer to part
    A).

21
Chemical Reactions
  • During chemical reactions, the chemical bonds of
    the REACTANTS (starting materials) are broken
    atoms are rearranged , and new bonds are formed
    in the PRODUCTS (end materials). Products have
    new properties.

REACTANTS
PRODUCTS
22
Chemical Reactions Law of Conservation of Mass
  • During chemical reactions, no matter (atoms) can
    be lost or gained. Atoms are just rearranged.

Coefficients of molecules
REACTANTS
PRODUCTS
Subscript atoms in molecule
23
  • Bonding Summary
  • Covalent bond? Ionic bond? Hydrogen bond? Polar
    covalent? Non-polar?
  • Hold elements in a compound together __________
  • Based on attraction between oppositely charged
    ions __
  • Bonds that form salts, like NaCl ____
  • Strong bonds formed by sharing electrons ____
  • Covalent bonds in which electrons are not equally
    shared results in partially charged molecules
    ____________
  • Atoms of H and O in water are held together by
    these _______
  • Individual water molecules are attracted to one
    another by these ________

24
CH. 4.3 Chemistry of Water
  • One of the few naturally occurring
  • compounds that is liquid at the temperatures
    found on the Earths surface.
  • Living organisms are 70 - 95 water

25
Water A Polar Molecule
  • Some molecules have an uneven distribution of
    electrons
  • Since Oxygen is a bigger atom (more protons) than
    the hydrogen atoms, the electrons spend more time
    near the oxygen
  • This creates a partial charge on each end
  • Polar molecules have charged ends (like a
    magnets polarity)
  • Overall the molecule is neutral (no charge)

26
Water Hydrogen Bonds
  • Because of their partial positive negative
    charges, polar molecules like water can attract
    each other.
  • The hydrogen atom of one water being attracted to
    the oxygen atom of another water is an example of
    hydrogen bonding.

27
Properties of Water Water is a SOLVENT
  • Water is an excellent SOLVENT (It dissolves
    things).
  • Things that dissolve(salts, sugar) SOLUTES.
  • The partial charges in water (POLARITY) attract
    the charges in other substances this pulls them
    apart (DISSOLVE)
  • Polar molecules and salts dissolve in water. Non
    polar substances (oil, etc. do not dissolve)
  • Importance
  • Water is main solvent in cells, blood, etc.
  • Dissolved substances are transported by blood and
    lymph

28
  • Properties of Water Moderate Temperature Change
  • High Heat Capacity resists change in
    temperature (a lot of energy stored/released for
    temp change)
  • High Heat of Vaporization evaporation requires
    a lot of energy water stays a liquid on Earth
  • Both of these properties are due to H-bonding of
    water.
  • When warming up water, absorbed energy is used to
    BREAK H-BONDS then temps. can change.
  • When temps. decrease H-Bonds form. This
    releases energy and keeps temps from dropping
    rapidly.
  • Results Oceans absorb release heat slowly,
    preventing rapid climate/temp. change!

29
Properties of Water Cohesion, Adhesion
Capillary Action
  • Cohesion attraction (by H-bonding) between two
    molecules of the same polar substance (Water
    sticks to itself beads up)
  • Adhesion attraction (by H-bonding) between two
    molecules of the different polar substances
    (Water sticks to other things wets them).
  • Capillary Action Water moves up a tube b/c it
    is attracted to the sides.

Water moves from roots to shoots in trees. Water
is attracted to walls of xylem (tubes of tissue
analogous to our veins) by ADHESION. Water
molecules pull each other along COHESION
30
Surface Tension
Film-like surface of water due to cohesion at
the surface.
31
Solutions
  • Solution a homogenous mixture in which one
    substance is dissolved into another
  • A solute (like sugar) completely dissolves in a
    solvent (like water) like in iced tea.
  • Water is the best (universal) solvent due to its
    polarity (charged ends)
  • Blood is mostly water. Bloods job distribute
    dissolved substances throughout body.

32
(No Transcript)
33
Water acts like a magnet.
34
Suspensions
  • Materials do not break up into individual atoms,
    but particles are small enough that they do not
    settle on the bottom of a container.
  • Example blood

35
Solutions Acids
  • When some compounds dissolve
  • in water, they break apart into
  • individual ions.
  • HCl ? H Cl-
  • Compounds that release hydrogen ions (H) into a
    solution are acids High H
  • means concentration of
  • Characteristics of Acids (do not write)
  • Produce H (H3O) ions in water
  • Taste sour
  • Corrode metals
  • React with bases to form salts and water
  • Are electrolytes

36
Solution Bases
  • Bases are compounds that release
  • hydroxide ions (OH-) into a solution
  • NaOH ? Na OH-
  • Produce OH- ions in water or pick up/remove H
    ions
  • Characteristics of Bases (do not write)
  • Taste bitter, chalky
  • Are electrolytes (produce electricity)
  • Feel soapy, slippery
  • React with acids to form salts and water

37
  • pH Scale measure how acidic or basic a solution
    is.
  • 7 is a neutral pH
  • H OH-
  • pH lt 7 acid (high concentration H)
  • pH gt 7 base (low concentration H)
  • Farther pH from 7, the more acidic or basic
  • Every change in pH value corresponds to a
    ten-fold change in H
  • pH 3 is 10x more acidic than pH 4 and 100x more
    acidic than pH 5

38
pH Self Assessment
  • Strong acid? Weak acid? Neutral? Weak base?
    Strong base?
  • High H?
  • High pH ?
  • H OH-?

39
Buffers
  • Substances that resist changes in pH.
  • Important in living organisms where change in pH
    can be deadly (Blood contains bicarbonate ion
    buffers)
  • When pH drops, buffers remove Hions
  • When pH rises, buffers add H ions
  • Helps to maintain homeostasis

40
Water Molecule Models
  • 1. Red circle ____ White circle _______
  • Sketch water molecule. Label () and (-) ends.
  • Explain WHY water has a () and (-) end.
  • Sketch how water molecules attract other water
    molecules. Label the hydrogen bond in your
    drawing.
  • Is ethane (C2H6) polar or non polar? Provide a
    reason.
  • Which end of a water molecule would be attracted
    to an Na ion?

41
(No Transcript)
Write a Comment
User Comments (0)
About PowerShow.com