1. CHEMISTRY

2. Composition of Matter
Matter - Everything in the universe is composed of matter
Matter is anything that occupies space or has mass
Mass – quantity of matter an object has
Weight – pull of gravity on an object
130 lbs. = 58967g

3. Elements
Pure substances that cannot be broken down chemically into simpler kinds of matter

4. 90% of the mass of an organism is composed of 4 elements (oxygen, carbon, hydrogen and nitrogen)
Each element unique chemical symbol
Consists of 1-2 letters
First letter is always capitalized

5. Atoms
The simplest particle of an element that retains all the properties of that element
Properties of atoms determine the structure and properties of the matter they compose

6. The Nucleus Central core
Consists of positive charged protons and neutral neutrons
Positively charged
Contains most of the mass of the atom

7. The Protons
All atoms of a given element have the same number of protons
Number of protons called the atomic number
Number of protons balanced by an equal number of negatively charged electrons

8. The Neutrons
The number varies slightly among atoms of the same element
Different number of neutrons produces isotopes of the same element

9. Isotope
Different number of neutrons

10. The Electrons
Negatively charged high energy particles with little or no mass
Travel at very high speeds at various distances (energy levels) from the nucleus

11. Electrons in the same energy level are approximately the same distance from the nucleus
Outer energy levels have more energy than inner levels
Each level holds only a certain number of electrons

12. Atomic Mass Protons & neutrons are found in the nucleus of an atom
The atomic mass of an atom is found by adding the number of protons & neutrons in an atom

13. Compounds
Most elements do not exist by themselves
Readily combine with other elements in a predictable fashion based on valence electrons

14. Chemical formulas show the kind and proportion of atoms of each element that occurs in a particular compound

15. Molecules are the simplest part of a substance that retains all of the properties of the substance and exists in a free state
Some molecules are large and complex

16. The physical and chemical properties of a compound differ from the physical and chemical properties of the individual elements that compose it

17. The tendency of elements to combine and form compounds depends on the number and arrangement of electrons in their outermost energy level
Atoms are most stable when their outer most energy level is filled

18. Most atoms are unstable in their natural state
Tend to react (combine) with other atoms in order to become more stable (undergo chemical reactions)
In chemical reactions bonds are broken; atoms rearranged and new chemical bonds are formed that store energy

20. Covalent Bonds
Formed when two atoms share one or more pairs of electrons

21. Ionic Bonds Some atoms become stable by losing or gaining electrons
Atoms that lose electrons are called positive ions (cation)
Na would become an ion when it gives away its electron to Cl

22. Atoms that gain electrons are called negative ions (anions)

23. Atoms vs. Ions

24. States of Matter Atoms are in constant motion
The rate at which atoms or molecules in a substance move determines its state

25. Energy and Chemical Reactions
Living things undergo thousands of chemical reactions as part of the life process

26. Chemical equations represent chemical reactions
*Chemical equations represent chemical reactions. *The number atoms must be the same on each side. *Bonds may be broken or formed

27. Energy Transfer
Much of the energy organisms need is provided by sugar (food)
A series of chemical reactions take place in which energy is released (cellular respiration)
The net release of free energy is called an exergonic (exothermic) reaction

28. Reactions that involve a net absorption of free energy are called endergonic (endothermic) reactions
Most reactions in living organisms are endergonic; therefore living organisms require a constant source of energy

29. Most chemical reactions require energy to begin
The amount of energy needed to start the reaction is called activation energy

30. Catalysts reduce the amount of activation energy required
Biological catalysts are called enzymes

31. Enzymes are an important class of catalysts in living organisms
Mostly protein
Thousands of different kinds
Each specific for a different chemical reaction

32. Enzyme Structure Enzymes work on substances called substrates
Substrates must fit into a place on an enzyme called the active site
Enzymes are reusable!

33. Reduction-Oxidation Reactions
Many of the chemical reactions that help transfer energy in living organisms involve the transfer of electrons
Oxidation reaction – reactant loses electron(s) becoming more positive

34. Reduction reaction – reactant gains electron(s) becoming more negative

35. Reduction/Oxidation