1. The Chemistry of Life

3. General Chemistry Life depends on chemistry – Organisms are made matter – When you eat food or inhale oxygen, your body uses these materials in chemical reactions that keep you alive – Physical and chemical properties of matter affects living things – What elements are most abundant in living things? (p.20) C, H, O, N P, Na, Mg, K, Fe, Zn

4. Elements & Atoms Matter is made of elements – Periodic table of elements Atom = basic unit of matter Atoms can react to form molecules and compounds The subatomic particles that make up atoms are protons, neutrons, and electrons

5. The Parts of an Atom Nucleus – Contains protons & neutrons Orbitals (around nucleus) – contain electrons – also called clouds or shells Shell info for bio: 2, 8, 8

6. Atoms Atomic number- tells # of protons (which determines the identity of an atom; ex- any atom that has 6 protons is carbon) – Also tells the # of electrons in a neutral atom (+ = -) – Ions will have charges Mass number- tells # of protons plus the number of neutrons – Isotopes contribute to atomic weight Atomic Number Atomic weight

7. Atoms Practice Periodic table on p.20 & A-6 Practice drawing the following atoms: – F – N – Na – Ar

8. Isotopes Atoms of an element can have different numbers of neutrons. Atoms of the same element that differ in the number of neutrons they contain are known as isotopes.

9. Uses of Isotopes Nuclear Power Radiometric dating Radioactive tracers Irradiation of food

10. Chemical Compounds A chemical compound is a substance formed when two or more elements combine in definite proportions (given in molecular formulas) Ex: NaCl is 1 Sodium : 1 Chlorine H 2 O is 2 Hydrogen : 1 Oxygen

11. Molecules The structure that results when atoms are joined together is called a molecule. Molecules can form when similar or different atoms are joined. – Ex: O 2 and H 2 O What’s the difference between a molecule and a compound?

12. Element, Molecule, Compound Practice NameTotal # atoms# elements (count type of atoms) E, M, C (more than 1 may apply) Cd Fe 2 O 3 NH 3 O2O2 K 2 SO 4 N2N2 U

13. Chemical Bonds The atoms in molecules and compounds are held together by chemical bonds. – Chemical reactions make & break bonds – Activation energy (later chapter) Bond formation involves valence electrons The main types of chemical bonds are ionic bonds and covalent bonds. – The type of bond an atom forms depends on its electronegativity

14. Ionic Bonds An ionic bond is formed when one or more electrons are transferred from one atom to another. An atom that loses electrons has a positive charge (cations). An atom that gains electrons has a negative charge (anions). These positively and negatively charged atoms are known as ions.

15. Ionic Bonding between Sodium and Chlorine. The chemical bond in which electrons are transferred from one atom to another is called an ionic bond. The compound sodium chloride forms when sodium loses its valence electron to chlorine. These oppositely charged particles are highly attracted to each other.

16. Important Biological Ions Ca 2 + K+ Na+ Mg 2 + Cl - OH -

17. Covalent Bonds A covalent bond forms when electrons are shared between atoms. The electrons actually travel in the shells of both atoms. When the atoms share two electrons, the bond is called a single bond Sometimes the atoms share four electrons and form a double bond. In a few cases, atoms can share six electrons and form a triple bond.

18. Types of Covalent Bonds Polar Covalent – Unequal sharing – H 2 O Nonpolar Covalent – Equal sharing – O 2

19. Van der Waals Force- ADD TO NOTES When molecules are close together, a slight attraction can develop between the oppositely charged regions of nearby molecules. Chemists call these van der Waals forces Although van der Waals forces are not as strong as ionic bonds or covalent bonds, they can hold molecules together, especially when the molecules are large.

20. Van der Waals Force- WOW!! A gecko foot like the one shown at right is covered by as many as half a million tiny hairlike projections. Van der Waals forces form between molecules on the surface of the gecko's foot and molecules on the surface of the wall. The combined strength of all the van der Waals forces allows the gecko to balance the pull of gravity.

21. The Water Molecule H 2 O – 2 hydrogen (small; 1 proton each) – 1 oxygen (large; 8 protons) highly electronegative – Covalent bond Unequal sizes, unequal sharing  polar Slight charges (O - & H + ) – Hydrogen bonds Weak attractions between charges

22. Law of Conservation of Matter Matter is neither created nor destroyed – Matter can change form or location SnO 2 + H 2 → Sn + H 2 O – Unbalanced (O) SnO 2 + H 2 → Sn + 2 H 2 O – Still unbalanced (H) SnO 2 + 2 H 2 → Sn + 2 H 2 O – Balanced! Read as 1, 2, 1, 2

23. Properties of Water Water is essential to life as we know it The water that exists on Earth today has been here for millions of years (water cycle) Water’s polarity and the resulting hydrogen bonds are biologically important

24. Chemical Bonds Link Atoms Hydrogen bonds give water unique properties, and they are important in protein and DNA structure. Water © McGraw-Hill Education/Jacques Cornell Photographer

25. Cohesion and Adhesion Cohesion- attraction between “same” molecules Surface tension created by cohesion Adhesion- attraction between different molecules Capillary action pulls water up celery using adhesion

26. Water Has Many Unique Properties Together, cohesion and adhesion allow water molecules to “climb” from a tree’s roots to its highest leaves. Beach: © Getty Images/flickr RF

27. Mixtures, Solutions, and Suspensions Mixtures- – Physical combination of elements or compounds Not a chemical change Give an example Suspensions- – Sand + water Define Solutions- – Pic on right, what is the: Solute? Define Solvent? Define – Universal solvent = ?

28. Hydrophilic vs Hydrophobic

30. Water has a high specific heat. Specific heat is the amount of energy required to change the temperature of a substance. Because water has a high specific heat, it can absorb large amounts of heat energy before it begins to get hot. It also means that water releases heat energy slowly when situations cause it to cool. Water's high specific heat allows for the moderation of the Earth's climate and helps organisms regulate their body temperature more effectively. Water Has Many Unique Properties Water has a high specific heat

31. Water Has Many Unique Properties Water regulates temperature Because water has a high specific heat, it regulates temperature. -Hydrogen bonds make water resist changes in temperature. -Coastal regions have milder temperatures than landlocked regions. -Sweating cools the body.

32. Water Has Many Unique Properties Water expands when it freezes Water expands when it freezes. -Ice is less dense than liquid water. -Aquatic life survives the winter.

33. Water participates in life’s chemical reactions More about this in the biochemistry section of this chapter

34. pH Scale Actually a “log” scale- 10 fold changes – Ex- 10 4 Acids- 0-6 – More H+ ions (hydrogen) Bases (alkaline)- 8-14 – More –OH ions (hydroxide) Neutral- 7 Litmus paper- color indicates pH

35. Buffers Homeostasis review Most of your cells need pH to fall between about 6.5-7.5 Buffers help control pH to prevent sharp changes Click for buffer clip (intro only ~2.5 mins)