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Chemistry Comes to Life - The Nature of Atoms, Compounds, Water, & Major Molecules of Life

This lecture presentation covers the nature of atoms, compounds and chemical bonds, the role of water in life, and the major molecules of life. Topics include atomic structure, isotopes, covalent and ionic bonds, water's unique properties, acids and bases, pH, buffers, and biological macromolecules.

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Chemistry Comes to Life - The Nature of Atoms, Compounds, Water, & Major Molecules of Life

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  1. Chapter 2 Chemistry Comes to Life Lecture Presentation Betty McGuireCornell University

  2. Chemistry Comes to Life • The nature of atoms • Compounds and chemical bonds • The role of water in life • Major molecules of life

  3. The Nature of Atoms • Everything that takes up space and has mass is called matter

  4. The Nature of Atoms • All matter is made of atoms, each containing a nucleus with protons and neutrons surrounded by a cloud of electrons • Atoms are units of matter that cannot be broken down into simpler substances by ordinary chemical means

  5. The Nature of Atoms • Element • A form of matter that cannot be broken down into simpler substances • Made of many atoms that are all the same

  6. The Nature of Atoms • Each element has an atomic number and atomic weight • Atomic number • The number of protons in the nucleus • Atomic weight • The number of protons plus the number of neutrons

  7. The Nature of Atoms • Elements with the same number of protons but different numbers of neutrons are called isotopes • All carbon atoms have six protons in the nucleus • Common isotopes of carbon include 12C (with six neutrons), 13C (with seven neutrons), and 14C (with eight neutrons)

  8. The Nature of Atoms • Radiation is energy moving through space, such as radio waves, light, and heat • Some elements have both stable and unstable isotopes • A radioisotope is unstable and emits radiation • Radiation can be very harmful, causing the death of cells, or very beneficial, as evidenced by its use in medicine

  9. Compounds and Chemical Bonds • Two or more elements may combine to form a compound • A compound’s characteristics are usually different from those of its elements

  10. Compounds and Chemical Bonds • The atoms in a compound are held together by either covalent or ionic bonds • When atoms form bonds, they lose, gain, or share electrons in their outermost shell

  11. Compounds and Chemical Bonds • Covalent bonds • The strongest bonds • They form when two or more atoms share the electrons in their outer shells

  12. Compounds and Chemical Bonds • Molecule • A chemical structure held together by covalent bonds • The chemical structure shows the number of each element forming the molecule

  13. Compounds and Chemical Bonds • Ion • An atom or group of atoms with a positive or negative electrical charge • Ionic bonds • Weaker than covalent bonds • Result from the attraction of oppositely charged ions, rather than shared electrons

  14. The Role of Water in Life • When the electrons of a covalent bond are shared unequally, the bond is called polar • The resulting molecules are called polar molecules • Water is a polar molecule • Its unique properties such as its high heat capacity, its high heat of vaporization, and its superior ability as a dissolving agent can be traced to its polarity

  15. The Role of Water in Life • Hydrogen bonds • The attraction formed between a slightly positively charged hydrogen atom and another slightly negatively charged atom

  16. The Role of Water in Life • Hydrogen bonds account for the unique properties of water and the geometric shape of many biological molecules

  17. The Role of Water in Life Web Activity: Water and Chemistry

  18. The Role of Water in Life • Acids and bases react differently to water • Acids release hydrogen ions (H+) when placed in water • Bases produce hydroxide ions (OH–) when added to water

  19. The Role of Water in Life • pH • The negative logarithm of the concentration of the H+ ion in solution • The lower the pH on the pH scale, the greater the acidity • The higher the pH, the more basic a solution

  20. The Role of Water in Life • Buffers • Prevent dramatic changes in pH • Remove excess H+ from solutions when concentrations of H+ increase • Add H+ when concentrations of H+ decrease • Many body fluids have the buffering capacity to maintain a constant internal environment

  21. The Role of Water in Life • Acid rain • Usually defined as rain with a pH lower than 5.6, the pH of natural precipitation • Caused largely by the burning of fossil fuels in cars, factories, and power plants • Has devastating effects on the environment

  22. Major Molecules of Life • Biological macromolecules • The giant molecules of life • They are long chains called polymers made of repeating units called monomers

  23. Major Molecules of Life • When polymers are made, water is removed, and the reaction is called dehydration synthesis

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