Chemistry of Life

1. Chemistry of Life

2. What’s the Matter? Atom: The most basic unit of matter • Not all atoms are the same Elements: a pure substance that consists of one type of atom. • Represented by a one or two letter symbol • 90 naturally occurring, 22 synthetic • Of the 90 naturally occuring, only 25 are needed by life. • CHON makes up 96% of these 25. • The different elements are determined by amount and arrangement of sub- atomic particles.

3. Subatomic Particles Nucleus: Center of Atom (+ Charge) • Protons (+ charge) • Neutrons (0 charge) Cloud: around the nucleus • Electrons (- charge)

4. The Electron Cloud Electrons are moving around the nucleus at distinct energy levels (shells, or orbitals) Each energy level has a limited capacity of electrons. • 1st (closest to nucleus) = 2 electron max • 2nd and higher = 8 electron max In their most isolated state, atoms have equal numbers of electrons and protons so that they have no overall charge

5. Atomic Properties Atomic Number: The number of protons in the nucleus. • Determines which element is which • Also indicates how many electrons will be found in the cloud for that element. Mass Number (Atomic Mass): The overall mass of the atom of that element • Sum of the number of protons and the number of neutrons.

6. Knowing the atomic number and the mass number, how could you determine the number of neutrons in the nucleus of an atom? • Mass # - Atomic # = number of neutrons • Isotopes

7. The Octet Rule Atoms interact with each other in order to fill their outer most energy level with electrons. (usually eight) • Most atoms do not have full outer shells • Does CHON? • This causes atoms to react with other atoms (by forming bonds) to form compounds.

9. Chemical Bonds The emergent properties of a compound.  The metal sodium combines with the poisonous gas chlorine to form the edible compound sodium chloride, or table salt.

10. Compounds A substance formed by the chemical combination of two or more elements in definite proportions. • Formed due to the needs of atoms to have outer shells that are full with electrons. • Nearly all matter on this planet exists in the form of compounds • What are the exceptions? ( hint: look at the periodic table)

11. Types of bonds 1)Ionic Bonds: A bond that forms when electrons are transferred from one atom to another. • When atoms gain or lose electrons they become charged atoms called ions. • The opposing charges of ions cause the bond to form. • How does sodium (Na) and chlorine (Cl) interact? (hint: draw bhor models)

12. Mostly abiotic factors form and break Ionic bonds Ca & Cl (hint: think of quantity of atoms needed)

13. Types of Bonds 2) Covalent Bonds: A bond that forms between atoms when electrons are shared. • The electrons actually travel in the orbitals of both atoms aka “shared”. • Ex. H & O, C & H, N & H, O &O • Can have single covalent bonds (2 e-), double covalent bonds (4 e-) or Triple(6e-) • Molecules: Compounds that are held together by covalent bonds. • Typically biotic factors form and break covalent bonds.

15. Water as a Molecule

16. Water is a polar molecule Polarity: When the sharing of electrons in a molecule is uneven. This results in the molecule having a slight negatively charged side and a slight positively charged side

17. Hydrogen Bonds Because of their differing charges on either side, polar molecules (like water) can form hydrogen bonds. • Week bond between the hydrogen of one polar molecule and the oxygen from another polar molecule

18. Hydrogen bonds between water molecules.  The charged regions of a polar water molecule are attracted to oppositely charged parts of neighboring molecules. Each molecule can hydrogen–bond to multiple partners, and these associations are constantly changing. At any instant in liquid water at 37ºC (human body temperature), about 15% of the molecules are bonded to four partners in short–lived clusters.

19. Ice: crystalline structure and floating barrier.  In ice, each molecule is hydrogen–bonded to four neighbors in a three–dimensional crystal. Because the crystal is spacious, ice has fewer molecules than an equal volume of liquid water. In other words, ice is less dense than liquid water. Floating ice becomes a barrier that protects the liquid water below from the colder air. The marine organism shown here is called a euphausid shrimp; it was photographed beneath the Antarctic ice.

20. Cohesion and Adhesion Cohesion: The attraction between molecules of the same substance • Due to hydrogen bonding • Results in the high surface tension of water Adhesion: The attraction between molecules of different substances. • Meniscus in a graduated cylinder.

21. Walking on water.  The high surface tension of water, resulting from the collective strength of its hydrogen bonds, allows the water strider to walk on the surface of a pond. Due to what property of water?

22. Why is it unlikely that two neighboring water molecules would be arranged like this?

23. Copy this chart down on a separate sheet of paper

24. Acids, Bases, and pH Acids: any compound that forms H+ ions in a solution. Bases: any compound that forms OH- ions in a solution. The pH scale: A measurement system that uses the concentrations of H+ ions and OH- ions in a solution

26. Chemical Reactions A process where one set of compounds are changed, or transformed into other different compounds

27. Parts of a Chemical Reaction Reactants: The elements or compounds that enter a reaction or the starting materials in a chemical reaction Products: The elements or compounds that are produced by a chemical reaction or the ending materials of a reaction.

28. Types of reactions Exergonic Reactions: a type of reactions that releases energy. • When the energy of the reactants are greater (bigger molecules) than the energy of the products (smaller molecules). • Happen spontaneously Endergonic Reactions: a type of reaction where an input of energy is needed for the reaction to occur. • When the energy of the reactants are less (smaller molecules) than the energy of the products (bigger molecules).

29. Copy down this chart on a blank sheet of paper

30. Reaction Demo Make observations about the properties of the reactants to reactions A and B. • State of matter, color, texture, etc. Make observations about the reaction as it takes place • Change of color, noticeable visual action, change of state, heat released or absorbed, etc. Using your initial and final observations describe what you observed. Be sure to include reaction type, and a prediction of the sizes of the reactant compounds and the sizes of the product compounds after the reaction took place

31. Reactions and the First Law Matter can neither be created nor destroyed, it can only be transformed. • Because of this all atoms in a reaction must be accounted for. • All types and amounts of the atoms on the reactants side must equal the types and amounts of the atoms on the products side. • You can change the amount of a compound by adding coefficients to the front of a compound. You CANNOT change the compound itself by adding numbers in-between or under the elements of a compound.

32. Practice Indicate the # of Atoms, Compounds, and Elements in each of the following: 5H2SO4 6Na3BO3 10AgNO3 Try to balance this simple reaction by adding coefficients H2 + O2 H2O

34. Practice H2 + N2 NH3 CH4 + O2  CO2 + H2O H2CO3  CO2 + H2O CO2 + H2O  C6H12O6 + O2

35. Photosynthesis: a solar–powered rearrangement of matter.  Elodea, a freshwater plant, produces sugar by rearranging the atoms of carbon dioxide and water in the chemical process known as photosynthesis, which is powered by sunlight. Much of the sugar is then converted to other food molecules. Oxygen gas (O2) is a by–product of photosynthesis; notice the bubbles of oxygen escaping from the leaves in the photo.