Chapter 3: The Importance of Water
Vocabulary: polar molecule, cohesion, adhesion, surface tension, kinetic energy, heat, temperature, calorie, degrees Celsius, heat of vaporization, solvent, solute, solution, aqueous solution, hydration shell, hydrophilic, hydrophobic, colloid, mole, Avogadro's number, molarity, molar mass, hydrogen ion (H+), hydroxide ion (OH-), hydronium ion (H3O+), pH, acid, base, acidic solution, basic solution, neutral solution, buffer, precipitation, chemical equilibrium
Objectives:
After attending lectures and studying the chapter, the student should be able to:
1. Show the molecular formula and structural formula for water.
2. Explain why water molecules are polar.
3. Describe the hydrogen-bond between water molecules.
4. List the properties of water:
It is cohesive and adhesive
It has a high specific heat
It has a high heat of vaporization
It is less dense as a solid than a liquid
It is a good solvent
5. Distinguish between cohesion and adhesion of water molecules and describe the capillary
action process of water transport in plants.
6. Distinguish between the terms hydrophilic and hydrophobic, and state which types of
substances dissolve in water and which types do not.
7. Explain why liquid H2O is necessary for life on Earth.
8. Explain how water's high heat capacity is important to living things as a temperature buffer.
9. Explain why water's high heat of vaporization is important to living things as a temperature
stabilizer.
10. Ice floats. Explain why this is an unusual property, and give an example of how this is
important to living things.
11. Describe how water is used as the basis of the scientific measurements of temperature, mass,
and energy.
12. Describe an aqueous solution.
13. Define mole and be able to calculate grams to moles and moles to grams
of a given substance.
14. Describe how molarity can be used as a measure of concentration of aqueous solutions.
15. Describe how percentage can be used as a measure of concentration of aqueous solutions.
16. Calculate molarities and percentages of aqueous solutions.
17. Define pH and describe the pH scale.
18. Distinguish between acids and bases and give examples of each.
19. Describe how buffers maintain the pH of an aqueous solution and their importance in
in biological systems.
| 898162042 | Polar Molecule |  | 1 | |
| 898162043 | Cohesion | Water molecules stay close to each other as a result of hydrogen bonding. At any given moment, many of the molecules are linked by multiple hydrogen bonds. These linkages make water more structured than most other liquids |  | 2 |
| 898162044 | Adhesion | The linking together of like molecules, often by hydrogen bonds. |  | 3 |
| 898162045 | Surface Tension | A measure of how difficult it is to stretch or break the surface of a liquid. Water has a high surface tension because of the hydrogen bonding of surface molecules. | 4 | |
| 898162046 | Kinetic Energy | The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter. | 5 | |
| 901696708 | Evaporative Cooling | The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state. | 6 | |
| 898162047 | Heat | The total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter; also called thermal energy. Heat is energy in its most random form. | 7 | |
| 898162048 | Temperature | A measure of the intensity of heat in degrees, reflecting the average kinetic energy of the molecules. | 8 | |
| 898162049 | Calorie | The amount of heat energy required to raise the temperature of 1 g of water by 1°C; also the amount of heat energy that 1 g of water releases when it cools by 1°C. The Calorie (with a capital C), usually used to indicate the energy content of food, is a kilocalorie. | 9 | |
| 898162050 | Degrees Celsius | ... | 10 | |
| 898162051 | Heat of Vaporization | The quantity of heat a liquid must absorb for 1 gram of it to be converted from the liquid to the gaseous state. |  | 11 |
| 898162052 | Solvent | The dissolving agent of a solution. Water is the most versatile solvent known. | 12 | |
| 898162053 | Solute | A substance that is dissolved in a solution. | 13 | |
| 898162054 | Solution | A liquid that is a homogeneous mixture of two or more substances. | 14 | |
| 898162055 | Aqueous Solution | One in which water is the solvent | 15 | |
| 898162056 | Hydration Shell | The sphere of water molecules around each dissolved ion is called a hydration shell |  | 16 |
| 898162057 | Hydrophilic | Substances that have an affinity for water | 17 | |
| 898162058 | Hydrophobic | Susbstances that do not have an affinity for water | 18 | |
| 901696709 | Colloid | A mixture made up of a liquid and particles that (because of their large size) remain suspended rather than dissolved in that liquid. |  | 19 |
| 898162060 | Mole | The number of grams of a substance that equals its molecular weight in daltons and contains Avogadro's number of molecules. |  | 20 |
| 898162062 | Molarity | A common measure of solute concentration, referring to the number of moles of solute per liter of solution. Molarity (M) = moles solute/liters solution | 21 | |
| 902486877 | How do you calculate molarity? | To calculate molarity: 1. Calculate the number of moles of solute present. 2. Calculate the number of liters of solution present. 3. Divide the number of moles of solute by the number of liters of solution. |  | 22 |
| 898162061 | Avogadro's Number | 6.022 x 10^23 |  | 23 |
| 898162063 | Molar Mass or Molecular Mass | The sum of the masses of all the atoms in a molecule |  | 24 |
| 898162064 | Hydrogen Ion (H+) | Occasionally a hydrogen atom participating in a hydrogen bond between two water molecules shifts from one molecule to the other. When this happens, the hydrogen atom leaves its electron behind, and what is actually transferred is a hydrogen ion. (H+) is now a single proton with a charge of 1+ |  | 25 |
| 898162065 | Hydroxide Ion (OH-) | A water molecule that has lost a proton |  | 26 |
| 898162066 | Hydronium Ion (H3O+) | The water molecule that gains a proton, making that molecule H3O+ |  | 27 |
| 898162067 | pH | The pH of a solution is defined as the negative logarithm (base 10) of the hydrogen ion concentration |  | 28 |
| 898162068 | Acid | A substance that increases the hydrogen ion concentration of a solution. | 29 | |
| 898162069 | Base | A substance that reduces the hydrogen ion concentration of a solution. | 30 | |
| 898162070 | Acidic | A substance that increases the hydrogen ion concentration of a solution. | 31 | |
| 898162071 | Acidic Solution | ... | 32 | |
| 898162072 | Basic Solution | ... | 33 | |
| 898162073 | Neutral Solution | ... | 34 | |
| 898162074 | Buffer | A solution that contains a weak acid and its corresponding base. A buffer minimizes changes in pH when acids or bases are added to the solution. | 35 | |
| 898162075 | Precipitation | ... | 36 | |
| 898162076 | Chemical Equilibrium | ... | 37 | |
| 898162077 | Show the molecular formula and structural formula for water? | ... | 38 | |
| 898162078 | Explain why water molecules are polar? | ... | 39 | |
| 898162079 | Describe the hydrogen-bond between water molecules? | ... | 40 | |
| 898162080 | List 5 properties of water | It is cohesive and adhesive It has a high specific heat It has a high heat of vaporization It is less dense as a solid than a liquid It is a good solvent | 41 | |
| 898162081 | Distinguish between cohesion and adhesion of water molecules and describe the capillary action process of water transport in plants? | ... | 42 | |
| 898162082 | Distinguish between the terms hydrophilic and hydrophobic, and state which types of substances dissolve in water and which types do not. | ... | 43 | |
| 898162083 | Explain why liquid H2O is necessary for life on Earth | ... | 44 | |
| 898162084 | Explain how water's high heat capacity is important to living things as a temperature buffer | ... | 45 | |
| 898162085 | Explain why water's high heat of vaporization is important to living things as a temperature stabilizer | ... | 46 | |
| 898162086 | Ice floats. Explain why this is an unusual property, and give an example of how this is important to living things | ... | 47 | |
| 898162087 | Describe how water is used as the basis of the scientific measurements of temperature, mass, and energy | ... | 48 | |
| 898162088 | Describe an aqueous solution | ... | 49 | |
| 898162089 | Define mole and be able to calculate grams to moles and moles to grams of a given substance | ... | 50 | |
| 898162090 | Describe how molarity can be used as a measure of concentration of aqueous solutions | ... | 51 | |
| 898162091 | Describe how percentage can be used as a measure of concentration of aqueous solutions | ... | 52 | |
| 898162092 | Calculate molarities and percentages of aqueous solutions | ... | 53 | |
| 898162093 | Define pH and describe the pH scale | ... | 54 | |
| 901696710 | Celsius Scale | A temperature scale (°C) equal to 5/9(°F - 32) that measures the freezing point of water at 0°C and the boiling point of water at 100°C. | 55 | |
| 898162094 | Distinguish between acids and bases and give examples of each | ... | 56 | |
| 898162095 | Describe how buffers maintain the pH of an aqueous solution and their importance in biological systems | ... | 57 |
