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Chemistry of Life. Chapter 6. Atoms. Matter- anything that has mass and takes up space Atom- smallest particle into which a substance can be divided and still retain its chemical properties. What makes up an atom?. Proton- subatomic particle in atom that has positive charge

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  • Matter- anything that has mass and takes up space
  • Atom- smallest particle into which a substance can be divided and still retain its chemical properties
what makes up an atom
What makes up an atom?
  • Proton- subatomic particle in atom that has positive charge
  • Neutron- subatomic particle in atom that has no charge
  • Electron- subatomic particle in atom that has negative charge
understanding atoms
Understanding atoms
  • Nucleus- center of the atom where protons and neutrons are located
  • Electrons are found in the electron cloud
understanding atoms1
Understanding atoms
  • Element- atoms with the same atomic number have the same chemical properties
  • Isotopes- Atoms that have the same number of protons but different numbers of neutrons
uses of radioactive isotopes
Uses of radioactive Isotopes
  • Medical
    • Tracer- a radioactive substance that is taken up and used by the body
    • Ex. An overactive thyroid gland may be a symptom of cancer and can easily be detected using radioactive tracers
  • Elements can combine to form more complex structures
  • Compound- is a pure substance formed when two or more different elements combine
combining atoms
Combining atoms
  • Covalent bond-chemical bonds that forms when electrons are shared
  • Molecule- is a compound held together by covalent bonds
ionic bonds
Ionic bonds
  • Ionic Bond- chemical bond between two atoms that are attracted to each other by opposite charges
  • Think of how the positive and negative pole of a magnet attract
van der waals forces
Van der Waals forces
  • Van der Waals forces- attractive forces between positive and negative regions pull on molecules and hold them together
chemical reactions
Chemical Reactions
  • Chemical reactions- process by which atoms or groups of atoms in substances are reorganized into different groups
  • Reactants- starting substances
    • Left side of the arrow
  • Products- substance formed during reaction
    • Right side of the arrow
chemical reactions1
Chemical reactions

2H2 + O2 2H20




chemical reactions2
Chemical reactions
  • Activation energy- minimum amount of energy needed to start reaction
  • Enzyme- protein that can speed up the reaction
hydrogen bonds
Hydrogen bonds
  • Hydrogen bond- weak chemical bonds of a very special sort; play a key role in biology
  • A hydrogen bond occurs when the positive end of one polar molecule is attracted to the negative end of another
  • Think of two magnets
water s unique properties
Water’s unique properties
  • H2O- oxygen atom linked to two hydrogen atoms by single covalent bond
  • Water is a polar molecule
  • Hydrogen bonds allow these properties
water s unique properties1
Water’s unique properties
  • Heat storage
    • Many hydrogen bonds water molecules form together require large amount of thermal energy to disrupt organization
    • Water heats up slower than most compounds and holds temperature longer
water s unique properties2
Water’s unique properties
  • Ice Formation
    • If temperature is low enough, very few hydrogen bonds will break

Why is ice dense?

  • Hydrogen bonds keep water molecules spaced apart preventing them from approaching each other
water s unique properties3
Water’s unique properties
  • High heat of vaporization
    • Temperature is high enough, many hydrogen bonds break in water, changing it from a liquid to a gas
  • How does sweating cool you off?
water s unique properties4
Water’s unique properties
  • Cohesion- when a water molecule is attracted to another water molecule
  • Adhesion- when a water molecule is attracted to a different polar molecule
  • Capillary action is created by adhesion
water s unique properties5
Water’s unique properties
  • High polarity
    • Water molecules in a solution always try to form maximum hydrogen bonds possible
  • Hydrophilic- polar molecules that attracted to water molecules
  • Soluble- dissolve in water
  • Hydrophobic-nonpolar compounds shrink from contact with water
water and solutions
Water and solutions
  • Mixture- combination of two or more substances which each keeps its own properties
  • Homogenous mixture or solution- mixture that is uniform (same) composition



homogenous mixture
Homogenous mixture
  • Solvent- substance in which another substance is being dissolved
    • Water
  • Solute- substance that is dissolved in the solvent
    • powder
  • Acid- substances that release hydrogen ions (H+) when dissolved in water
  • Base- substance that release hydroxide ions (OH-) when dissolved in water
  • pH- concentration (amount) of H+ in a solution