Chemistry review. Energy levels: The six most abundant elements of life. Types of bonds. Atom:

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1 Atom: Chemistry review Energy levels: Energy Levels: move around the nucleus in regions. Different levels have different numbers of electrons. Outermost Energy Level: Atoms are most when they have a outermost energy level Composed of: The six most abundant elements of life Types of bonds Compound: Examples Covalent bonds: Molecules: Co = together Valent = power or strength 1 P a g e

2 A atom needs electrons to fill its energy level. An atom needs electron to fill its outermost energy level. In CO2, carbon makes a, or of electrons with each oxygen atom. Ions: Positive Ions: Negative Ions: Ionic bonds: 2 P a g e

3 1. Transfer of an electron from a sodium atom to a chlorine atom. Chlorine only needs electrons to have a / outer energy level, and since sodium only has electron in its outermost energy level, it. 2. The positive sodium ion and negative chloride ion attract each other. = ionic bond! Let s Practice a. Draw five protons in the nucleus of the atom. Label them with their charge. b. Draw six neutrons in the nucleus of the atom. c. Draw two electrons in the first energy level and label them with their charge. d. Draw three electrons in the second energy level and label them with their charge. e. What element is represented by the diagram? Label the information provided in the periodic table. What does the atomic number represent? or What does the atomic mass represent? + 3 P a g e

4 The Biological Importance of Water Why is water important? Major component of all living systems and our planet. Occupies most of a cell s volume. Has major properties that living systems require. Water is - made up of two elements, Neutral in charge and : unequal sharing of electrons, leading to a partially positive and partially negative charge. The atom is slightly and the atoms are slightly. are between the hydrogen and oxygen atoms, resulting in an uneven sharing of electrons = polarity. molecules form with other neighboring molecules. Each H 2O molecule can form with four other water molecules. Groups of hydrogen bonds are very, but bonds by themselves are. Also find hydrogen bonds holding our DNA and proteins together. Label the bonds! 4 P a g e

5 Polarity POLAR Asymmetrical: Examples: water, sugar, salt, ethanol, hydrogen sulfide The electrons of the polar covalent bonds spend more time near the oxygen than the hydrogen. allows water to form with each other. Ionic compounds dissolve in water to form ions: for most biological reactions to occur the reactants MUST dissolve in water. NONPOLAR Symmetrical: Strongly covalently bonded Examples: fats, oils, cell membranes and cell walls, carbon dioxide, gasoline. Water, the universal solvent a. almost all substances (mostly polar), and provides a in which other molecules can interact. b. : able to be dissolved, especially in water. c. Solution: uniform mixture of two or more substances. i. Solvent: substance present in the greatest amount. 1. Important solvents in your body: a.,,, ii. Solute: substance that dissolves in the solvent. 1. Important solutes in the body: a.,,, iii. Example: water = solvent, Kool-aid powder / sugar= solute, Kool-aid= solution Hydrophilic Hydrophobic Amphipathic Molecules have both polar and nonpolar regions. Ex- cell membrane 5 P a g e

6 Recall Questions?????? 1. What are the three major types of bonds?,, and 2. Which bond is the strongest? 3. Which bond is the weakest? 4. Which bond is the result of opposite charges attracting? 5. Which bond allows neighboring water molecules to attract to one another? 6. Which bond holds the hydrogen and oxygen together in a water molecule? 7. In water, is slightly positive, while is slightly negative. 8. List the six elements that are crucial for our biological survival. 9. Which molecule is considered the universal solvent? 10. Identify the solvent and solute in the table below. Solution Solvent Solute 11. List four solvents in your body. 12. List four solutes in your body. 6 P a g e

7 Water molecules. o Why? Causes: : creates a skin on the surface of the water. Examples: skipping rocks, rain drops beading up on a car, water droplets on a penny, and a spider walking on water. Examples: meniscus (graduated cylinder), wet microscope slides sticking together. Result of the of water molecules sticking to each other, and of water molecules sticking to another surface. Examples: o Drinking straw, food coloring added to water to dye flowers, and plants transporting water from roots to leaves. 7 P a g e

8 ; therefore, water must absorb more heat energy to increase temperature. Very important because our cells release a lot of heat, and water absorbs that heat, which allows us to regulate cell temperatures= HOMEOSTASIS. Specific heat is the energy required to raise 1g of water by 1ºC. Examples: oceans cool slower than land due to the high heat capacity of water. Vaporization= Water is changing from a liquid to a gas Liquid molecules enter the air Evaporation produces a must be broken before water can evaporate and this requires a lot of energy. Example: Evaporative cooling o sweating (humans) or panting (dogs) = dogs can t sweat through their skin, they pant to circulate air through their bodies to cool 8 P a g e

9 Water freezes= crystalline structure maintained by hydrogen bonding O C / 32 F = Maximum density of water = 4 C o Fun Fact- the water at the bottom of a lake or pond, in the winter, is almost always 4 C. Ice is than liquid water because the are positioned in a way that = lower density. When ice melts to liquid water, the structure collapses and the density of the liquid increases. Ecosystems: o Advantages: o If ice filled an entire lake or ocean, from bottom to top, all of the living organisms would die. o Also. In the spring, the ice melts; water sinks and pushes up the nutrient rich water. Draw a visual representation of each property of water. 9 P a g e

10 Property of Water Explanation of Property Phenomenon / Examples Cohesion Adhesion Surface Tension Capillary Action High Specific Heat High Heat of Vaporization Lower density when solid 10 P a g e

11 1. Covalently bonded water molecules ionize; the atoms dissociate (break apart) into ions. 2. When water ionizes or dissociates, it releases a small but equal number of H + and OH - ions; thus, its ph is neutral. 3. Water dissociates into hydrogen and hydroxide ions. H + = hydrogen = acid OH - = hydroxide = base 4. Acid molecules dissociate in water, releasing hydrogen ions (H + ). 5. Bases are molecules that take up hydrogen ions or release hydroxide ions. As a logarithmic scale, each lower unit has 10 times the amount of hydrogen ions as the next higher ph unit. 11 P a g e

12 Defined as: Properties: ph below 7 Stings on skin Tastes sour Corrosive Common Acids HCl: hydrochloric acid Citric acid Sulfuric acid Battery acid Urine Lemon juice Defined as: Properties: ph above 7 Strong bases can burn skin Tastes bitter Slippery Common Bases: Oven cleaner Toothpaste Human blood Pepto Bismol Windex Baking soda ph scale measure degrees of Measure Neutral is 7 o Example- water How is ph regulated in our bodies? Through - compounds that can bind H+ ions when the H+ concentration increases and can release an H+ ion when the H+ ion decreases. Buffer: Example: normal ph of blood is (slightly basic). Any small change could disrupt cells and could potentially be fatal. ph and our environment If ph is too high or low in our drinking water, it can alter homeostatic levels, and potentially kill wildlife. Acidic water in your pipes can get corroded, leaving contaminants in the water. 12 P a g e

13 Alter the function of enzymes. Controls cell processes such as metabolism. The closer the ph is to , the higher your level of health and ability to resist diseases. How do we test ph? ph paper- turns a color when placed in a substance. Phenolphthalein: when a drop is placed in the substance, the color of the substance will change. Bases turn purple. Acids remain the same. Litmus test: base turns blue / acid turns red. Red cabbage indicator: contains a water soluble pigment called anthocyanin that changes color when it is mixed with an acid or base. The pigment turns red in acidic environments and bluish-green in alkaline (basic) environments. Practice Questions 1. A student mixes strawberry koolaid and water. The ph was taken using an indicator, the ph was 5.4. What kind of solution is strawberry Koolaid? 2. In the koolaid mixture, what must there be more of, hydrogen ions or hydroxide ions? 3. A student adds an alka-seltzer tablet to the koolaid and stirs. The ph is now 8.3. What was released by the alka-seltzer tablet to cause this change? 4. Baking soda is a weak base. Hydrochloric acid is a strong acid. What would happen if these two were mixed? 5. Bromthymol blue is a chemical indicator that is blue in basic and neutral solutions, and turns greenish and then yellow as the solution becomes more and more acidic. Fill in what color you think bromthymol blue would be in each of the situations in the chart. Situation Ph Indicator Color Water directly out of tap ph =7.2 ph after exhaled air is blown through a straw into water for 5 min. ph after a snail has lived in water for three day ph with 2mL of bleach added to the water ph with instant coffee added to the water ph after an aquatic plant is grown in water for three days in bright sunlight ph=5.1 ph=5.8 ph=9.4 ph=5.0 ph= P a g e