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Chemistry

Chemistry. Atoms, Molecules, Ions, and Bonds. Atoms are the smallest units of matter that cannot be broken down by chemical means. Atoms consist of 3 parts Proton – positively charged and located in the nucleus Neutron – has no charge in is also located in the nucleus

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Chemistry

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  1. Chemistry

  2. Atoms, Molecules, Ions, and Bonds • Atoms are the smallest units of matter that cannot be broken down by chemical means. • Atoms consist of 3 parts • Proton – positively charged and located in the nucleus • Neutron – has no charge in is also located in the nucleus • Electron – negatively charge particle and is arranged outside the nucleus CHEMISTRY

  3. Atom CHEMISTRY

  4. Atoms, Molecules, Ions, and Bonds • Molecules are groups of two or more atoms held together by chemical bonds • Chemical bonds between atoms form because of the interaction of their electrons • The electronegativity of an atom, or the ability of an atom to attract electrons, helps determine the kind of bond that will form. • Atoms have 8 valence electrons CHEMISTRY

  5. Molecules CHEMISTRY

  6. Electronegativity CHEMISTRY

  7. Atoms, Molecules, Ions, and Bonds • There are three kinds of bonds • Ionic • Covalent • Nonpolar Covalent • Polar Covalent • Hydrogen CHEMISTRY

  8. Ionic Bonds • Ionic bonds form between two atoms when one or more electrons are transferred from one atom to another. • One atom has a much higher electronegativity (stronger pull) then the other atom and takes one of it’s electrons • The atom that gains an electron has a negative charge • The atom that loses an electron has a positive charge • Ions are atoms that have a + or – charge. • Sodium Chloride (Salt) is an example; Na⁺Cl⁻ Animation: Ionic Bonds CHEMISTRY

  9. Ionic Bond Na+ Cl– Na Cl Sodium ion (a cation) Chlorine ion (an anion) Chlorine atom (an uncharged atom) Sodium chloride (NaCl) CHEMISTRY

  10. Covalent Bonds • Covalent bonds form when electrons between atoms are shared. • Nonpolar covalent bonds form when electrons are shared equally. Occurs when atoms and electronegativity are identical such as oxygen gas (O2) • Polar covalent bonds forms when electrons are shared unequally. Atoms in this bond have different electronegativities and have an unequal distribution of the electrons such as water (H2O). O will be slightly negative and H will be slightly positive. • Think of gravity. The larger object has a greater pull • Does the moon circle the earth or do we circle the moon Animation: Covalent Bonds CHEMISTRY

  11. Nonpolar Covalent Bonds CHEMISTRY

  12. Polar Covalent Bonds CHEMISTRY

  13. Single Double, and Triple Covalent Bonds Single covalent, double covalent, and triple covalent bonds form when 2, 4, and 6 electrons are shared CHEMISTRY

  14. Hydrogen Bonds • Hydrogen bonds are week bonds between molecules. • They form when a positively charged hydrogen atom in one covalently bonded molecule is attracted to a negatively charged area of another covalently bonded molecule • Water is a polar covalent bond. • The oxygen atom has a slightly – charge and the hydrogen atom has a slightly + charge • The positive pole of the hydrogen atom forms a hydrogen bond to the negative pole around the oxygen of another water molecule. • Use the diagram on page 12 of your notes CHEMISTRY

  15. Hydrogen Bonds CHEMISTRY

  16. Electronegativity of Hydrogen Bond CHEMISTRY

  17. Properties of Water • The hydrogen bonding among water molecules contributes to 5 very important properties • Water is an excellent solvent • Water has a high heat capacity • Ice floats • Water has strong cohesion and high surface tension • Water has a strong adhesion Animation: Water Structure CHEMISTRY

  18. Solvent • Ionic substances are soluble (they dissolve) in water because the poles of the polar water molecules interact with the ionic substances and separate them into ions. • Covalent bonds are similarly soluble in water. • Substances that dissolve in water are hydrophilic (water loving) • Substances such as fats and oils that do not dissolve in water are hydrophobic (water fearing) • This is because they lack charges CHEMISTRY

  19. Salt and Water Na+ Cl– CHEMISTRY

  20. Heat Capacity • Water has a high heat capacity, changing temperature very slowly with changes in its heat content. • This is why oceans stay warm even if the surround air temperature is much cooler. • It takes a large amount of energy to warm water to a boil or cool water to freeze it. • When sweat evaporates from you skin, a large amount of heat is taken with it and you are cooled. CHEMISTRY

  21. Water Density • Most substances contract and become more dense when they freeze, however water expands and becomes less dense • Ice floats on water!!! • In the solid state of water, the weak hydrogen bonds between water molecules become rigid and form a crystal that keeps the molecules separated and less dense than the liquid form. • If ice didn’t float, what would our world be like?? CHEMISTRY

  22. Cohesion • Cohesion is the attraction between like substances. • It occurs in water because of the hydrogen bonding between water molecules. • The strong cohesion between water molecules produces a high surface tension. • This creates a water surface firm enough to allow insects to walk on water Animation: Water Transport CHEMISTRY

  23. Surface Tension CHEMISTRY

  24. Adhesion • Adhesion is the attraction of unlike substances. • Glue is an adhesive because it sticks to other substances. • When water adheres to the walls of narrow tubing or to absorbent solids like paper, it demonstrates capillary action. • This occurs when water rises up a tube. • Plants use capillary action to transport water from the roots to the leaves through the xylem. CHEMISTRY

  25. Cohesion vs. Adhesion CHEMISTRY

  26. Mercury is Cohesive CHEMISTRY

  27. Acids and Bases • An acid is any substance that increases the H+ concentration of a solution • A base is any substance that reduces the H+ concentration of a solution CHEMISTRY

  28. Acids and Bases CHEMISTRY

  29. pH Scale • The pH of a solution is determined by the relative concentration of hydrogen ions • Acidic solutions have pH values less than 7 • Basic solutions have pH values greater than 7 • Most biological fluids have pH values in the range of 6 to 8 CHEMISTRY

  30. pH Scale CHEMISTRY

  31. Organic Molecules • Organic molecule are those that have carbon atoms. • In living systems, large organic molecules called macromolecules may consist of hundreds or thousands of atoms. • Most macromolecules are polymers, molecules that consist of a single unit (monomer) repeated many times. CHEMISTRY

  32. Monomer & Polymer CHEMISTRY

  33. Carbon • Carbon is so important to life because of its ability to form four covalent bonds. • Complex molecules can be formed by stringing carbon atoms together in a single straight line or by connecting carbons together to form rings. • Changing the structures of these complex carbon molecules will change it functions •  or  the amount of carbons • Using different atoms bonded to the carbons such as N, O, H, and S. Animation: Carbon Skeletons CHEMISTRY

  34. Carbon CHEMISTRY

  35. Carbon Bonds CHEMISTRY

  36. Isomers • Isomers are compounds with the same molecular formula but different structures and properties: • Structural isomers have different covalent arrangements of their atoms • Geometric isomers have the same covalent arrangements but differ in spatial arrangements • Enantiomers are isomers that are mirror images of each other Animation: Isomers CHEMISTRY

  37. Functional groups • Many organic molecules share similar properties because they have similar clusters of atoms called functional groups. • Each functional group gives the molecule a particular property, such as acidity or polarity. CHEMISTRY

  38. Functional Groups • The seven functional groups that are most important in the chemistry of life: • Look over Figure 2-3. • You should know all of theses!!! CHEMISTRY

  39. Organic Molecules • There are 4 important classes of organic molecules • Carbohydrates • Lipids • Proteins • Nucleic Acids CHEMISTRY

  40. Carbohydrates • Carbohydrates are organic molecules composed sugar molecules • They are classified into 3 groups according to the number of sugar (saccharide) molecules present. • Monosaccharide – 1 sugar molecule • Disaccharide – 2 sugar molecules • Polysaccharide – multiple sugar molecules CHEMISTRY

  41. Monosaccharide • A monosaccharide is the simplest kind of carbohydrate. • It consists of a single sugar molecule such as fructose, glucose, or galactose • Sugar molecules have a formula (CH2O)n • For Glucose, n is 6, and it’s formula is C6H12O6 • Fructose is also , but as you can see in Figure 2-4, the placement or the carbon atoms is different giving it a different function. • There are 2 forms of Glucose (reversal of the O and OH) • α-glucose – starch & glycogen • β-glucose - cellulose • Even a very small change in the position of an atom may dramatically change the chemistry of a molecule CHEMISTRY

  42. Monosaccharides CHEMISTRY

  43. Disaccharide • A disaccharide consists of two sugar molecules joined by a glycosidic linkage. • glucose + fructose = sucrose (table sugar) • glucose + galactose = lactose (the sugar in milk) • glucose + glucose = maltose • They have a formula of C12H22O11 not C12H24O12 • What’s missing??? Animation: Disaccharides CHEMISTRY

  44. Disaccharide CHEMISTRY

  45. Dehydration and Hydration • Glucose and fructose lose a water molecule during the chemical reaction of forming sucrose. • A condensation reaction is when a simple molecule is lost during a chemical reaction. • A dehydration reaction is when a water molecule is lost. • These reactions occur when two molecules are combined to form one larger molecule. • Hydration reactions occur when a water molecule is added to a substance. • This causes the substance to split into two molecules Animation: Polymers CHEMISTRY

  46. Dehydration & Hydration Reactions CHEMISTRY

  47. Polysaccharide • A polysaccharide consists of a series of connected monosaccharides. • A polysaccharide is a polymer because it consists of repeating units of a monosaccharide. • There are 4 very important polysaccharides in Biology • Starch • Glycogen • Cellulose • Chitin CHEMISTRY

  48. Starch • Starch is a polymer of α-glucose molecules • It is the principal energy storage molecule in plant cells. • How is this energy made? • Where is it stored? CHEMISTRY

  49. Glycogen • Glycogen is also compose of α-glucose molecules. • It differs from starch by its pattern of polymer branching. • It is the major energy storage molecule in animal cells • Where is the energy stored? CHEMISTRY

  50. Starch Glucose and Glycogen CHEMISTRY

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