Water and Life PDF

Created by Turbolearn AI Water and Life 🌊 Polar Covalent Bonds in Water Molecules Water molecules are polar, meaning they have a slightly positive charge on one end and a slightly negative charge on the other. This is due to the unequal sharing of ele...

Created by Turbolearn AI Water and Life 🌊 Polar Covalent Bonds in Water Molecules Water molecules are polar, meaning they have a slightly positive charge on one end and a slightly negative charge on the other. This is due to the unequal sharing of electrons in the covalent bonds between oxygen and hydrogen atoms. Polar Covalent Bond: A type of covalent bond where the electrons are not shared equally between two atoms, resulting in a molecule with a slightly positive charge on one end and a slightly negative charge on the other. Hydrogen Bonding The polarity of water molecules allows them to form hydrogen bonds with each other. Hydrogen bonds are weak attractions between the partially positive hydrogen atoms of one water molecule and the partially negative oxygen atoms of another. Hydrogen Bond: A weak attraction between the partially positive hydrogen atom of one water molecule and the partially negative oxygen atom of another. Emergent Properties of Water The unique properties of water that contribute to its suitability for life are: Property Description The ability of water molecules to stick together, resulting in high Cohesion surface tension. Moderation of The ability of water to absorb and release heat energy, helping to Temperature regulate temperature. Expansion upon The unique property of water that causes it to expand when it freezes, Freezing making it less dense than liquid water. The ability of water to dissolve a wide variety of substances, making it Solvent Properties an ideal solvent for many chemical reactions. Cohesion and Adhesion Cohesion and adhesion are two important properties of water that help it to move up plants and support life. Cohesion: The attraction between water molecules, allowing them to stick together. Adhesion: The attraction between water molecules and other substances, such as plant cell walls. Moderation of Temperature Water's high specific heat capacity allows it to absorb and release heat energy, helping to regulate temperature. Specific Heat Capacity: The amount of heat energy required to change the temperature of a substance by 1°C. Page 1  Created by Turbolearn AI Expansion upon Freezing Water's unique property of expanding when it freezes makes it less dense than liquid water, allowing it to float on top of liquid water. Solvent Properties Water's polarity and ability to form hydrogen bonds make it an ideal solvent for many chemical reactions. Solvent: A substance that is capable of dissolving other substances. Acidic and Basic Conditions Acidic and basic conditions can affect living organisms, and water's pH plays a crucial role in maintaining a stable environment. Term Definition Acid A substance that increases the concentration of hydrogen ions (H+) in a solution. Base A substance that decreases the concentration of hydrogen ions (H+) in a solution. A measure of the concentration of hydrogen ions (H+) in a solution, with a pH of 7 being pH neutral. Buffers Buffers are substances that help to maintain a stable pH in a solution by minimizing changes in the concentration of hydrogen ions (H+). Buffer: A substance that helps to maintain a stable pH in a solution by minimizing changes in the concentration of hydrogen ions (H+). Ocean Acidification Human activities such as burning fossil fuels can lead to ocean acidification, which can have profound effects on marine ecosystems. Ocean Acidification: The decrease in the pH of the ocean due to the absorption of carbon dioxide (CO2) from the atmosphere.## Water Molecules and Hydrogen Bonding 💧 Polar Covalent Bonds in Water Molecules Water molecules are polar, meaning they have an uneven distribution of charge. This is due to the unequal sharing of electrons between the oxygen and hydrogen atoms in the covalent bonds. Polar covalent bond: a covalent bond in which the electrons are not shared equally between the two atoms, resulting in a partial positive charge on one atom and a partial negative charge on the other. The oxygen atom in a water molecule is more electronegative than the hydrogen atoms, so the electrons in the covalent bonds spend more time closer to the oxygen atom. This results in a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atoms. Page 2  Created by Turbolearn AI Hydrogen Bonding Hydrogen bonding is the attraction between the partial positive charge on a hydrogen atom and the partial negative charge on an electronegative atom, such as oxygen. Hydrogen bond: a weak electrostatic attraction between the partial positive charge on a hydrogen atom and the partial negative charge on an electronegative atom. Hydrogen bonds are responsible for the unique properties of water, including its high surface tension and ability to moderate temperature. Emergent Properties of Water Cohesion of Water Molecules Water molecules are held together by hydrogen bonds, which result in a phenomenon called cohesion. Cohesion: the attraction between molecules of the same substance, resulting in a tendency to stick together. Cohesion is responsible for the high surface tension of water, which allows it to behave as though it were coated with an invisible film. Property Description Surface The measure of how difficult it is to stretch or break the surface of a liquid. Tension The attraction between molecules of the same substance, resulting in a Cohesion tendency to stick together. Moderation of Temperature by Water Water is able to moderate temperature by absorbing heat from air that is warmer and releasing stored heat to air that is cooler. Specific Heat: the amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C. Water has a high specific heat, which means it can absorb or release a relatively large amount of heat with only a slight change in its own temperature. Unit Description Calorie (cal) The amount of heat it takes to raise the temperature of 1 g of water by 1°C. Kilocalorie 1,000 cal, the quantity of heat required to raise the temperature of 1 kg of (kcal) water by 1°C. Joule (J) 1 J = 0.239 cal, a unit of energy used to measure heat. Comparison of Specific Heat Values Substance Specific Heat (cal/(g°C)) Page 3  Created by Turbolearn AI Water 1 Ethyl Alcohol 0.6 Water's high specific heat is due to the energy required to break and form hydrogen bonds, which allows it to resist changing its temperature when it absorbs or releases heat.## Water's High Specific Heat 🌊 Water's high specific heat is the amount of heat per unit mass required to raise the temperature of water by 1 degree Celsius. This property allows large bodies of water to absorb and store a huge amount of heat from the sun in the daytime and during summer while warming up only a few degrees. Effects of Water's High Specific Heat Moderates air temperatures in coastal areas Stabilizes ocean temperatures, creating a favorable environment for marine life Helps regulate Earth's climate Allows organisms to resist changes in their own temperature Temperature Patterns in Coastal Areas Location Temperature (°F) Pacific Ocean 68 Santa Barbara 73 Los Angeles 75 San Diego 72 Burbank 90 Santa Ana 84 San Bernardino 100 Riverside 96 Palm Springs 106 Evaporative Cooling ❄️ Evaporative cooling is the process by which the surface of a liquid cools down as it evaporates. This occurs because the hottest molecules, those with the greatest kinetic energy, are the most likely to leave as gas. Heat of Vaporization The quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state. For water, the heat of vaporization is approximately 580 cal/g at 25°C. This is nearly double the amount needed to vaporize a gram of alcohol or ammonia. Page 4  Created by Turbolearn AI Effects of Evaporative Cooling Contributes to the stability of temperature in lakes and ponds Helps prevent terrestrial organisms from overheating Allows plants to regulate their temperature through transpiration Enables humans to cool down through sweating Floating of Ice on Liquid Water ❄️ Water is one of the few substances that are less dense as a solid than as a liquid. This is due to the hydrogen bonding between water molecules, which causes them to expand as they freeze. Density of Ice and Liquid Water State Density (g/cm³) Ice 0.92 Liquid Water (4°C) 1.00 Water as a Solvent 💧 A solution is a homogeneous mixture of two or more substances. The solvent is the dissolving agent, and the solute is the substance that is dissolved. Properties of Water as a Solvent Polarity of the water molecule allows it to dissolve a wide range of substances Ability to form hydrogen bonds with other molecules High dielectric constant, which allows it to dissolve ionic compounds Dissolution of Sodium Chloride (NaCl) in Water Sodium and chloride ions are attracted to the polar water molecules Water molecules surround the individual ions, separating and shielding them from one another The sphere of water molecules around each dissolved ion is called a hydration shell## Water as a Solvent 🌊 Water is a versatile solvent that can dissolve a wide variety of substances, including ionic compounds and polar molecules. This is due to its unique chemical properties, which allow it to form hydrogen bonds with other molecules. Hydrophilic and Hydrophobic Substances Hydrophilic substances have an affinity for water and can form hydrogen bonds with water molecules. Hydrophobic substances do not have an affinity for water and tend to repel it. "Hydrophilic" comes from the Greek words "hydro" meaning water and "philos" meaning loving. "Hydrophobic" comes from the Greek words "hydro" meaning water and "phobos" meaning fearing. Examples of hydrophilic substances include: Ionic compounds, such as sodium chloride (NaCl) Polar molecules, such as sugar (C12H22O11) Page 5  Created by Turbolearn AI Cellulose, a compound found in plant cell walls Examples of hydrophobic substances include: Vegetable oil Oils related to cell membranes Solute Concentration in Aqueous Solutions To understand chemical reactions in organisms, we need to know how many atoms and molecules are involved and calculate the concentration of solutes in an aqueous solution. Molecular mass is the sum of the masses of all the atoms in a molecule. Mole (mol) represents an exact number of objects: 6.021023, which is called Avogadro's number. Molarity is the number of moles of solute per liter of solution. Substance Molecular Mass (daltons) Molar Mass (g/mol) Sucrose (C12H22O11) 342 342 Ethyl alcohol (C2H6O) 46 46 To make a 1-molar solution of sucrose, we would measure out 342 g of sucrose and add water to a total volume of 1 L. Possible Evolution of Life on Other Planets 🚀 Astrobiologists search for life on planets that might have water. Water is essential for life as we know it, and its presence is a key indicator of a planet's potential for supporting life. Over 800 planets have been found outside our solar system, with evidence of water vapor on a few. Mars has been a focus of study, with evidence of water ice and liquid water present on the planet. Acidic and Basic Conditions ⚖️ Occasionally, a hydrogen atom participating in a hydrogen bond between two water molecules shifts from one molecule to the other, resulting in the formation of a hydrogen ion (H+) and a hydroxide ion (OH-). "Acidic" refers to a solution with a high concentration of hydrogen ions (H+). "Basic" refers to a solution with a high concentration of hydroxide ions (OH-). The pH scale is used to describe the acidity or basicity of a solution. pH Description 0-1 Strongly acidic 2-3 Acidic 4-5 Weakly acidic 6-7 Neutral Page 6  Created by Turbolearn AI 8-9 Weakly basic 10-12 Basic 13-14 Strongly basic Changes in pH can drastically affect a cell's proteins and other complex molecules.## Acids and Bases 🧬 Definition of Acids and Bases Acid: A substance that increases the hydrogen ion concentration of a solution. Base: A substance that reduces the hydrogen ion concentration of a solution. Types of Acids and Bases Strong Acids: Completely dissociate in water, releasing a high concentration of hydrogen ions. Example: Hydrochloric acid (HCl) Weak Acids: Partially dissociate in water, releasing a low concentration of hydrogen ions. Example: Carbonic acid (H2CO3) Strong Bases: Completely dissociate in water, releasing a high concentration of hydroxide ions. Example: Sodium hydroxide (NaOH) Weak Bases: Partially dissociate in water, releasing a low concentration of hydroxide ions. Example: Ammonia (NH3) pH Scale 📊 pH Value H+ Concentration (M) OH- Concentration (M) Description 0-1 High Low Strongly acidic 2-3 High Low Acidic 4-5 Medium Medium Weakly acidic 6-7 Low High Neutral 8-9 Low High Weakly basic 10-12 Low High Basic 13-14 Low High Strongly basic pH Calculation The pH of a solution is calculated using the formula: pH = -log[H+] Where [H+] is the concentration of hydrogen ions in moles per liter (M). Buffers 🧬 A buffer is a substance that minimizes changes in the concentrations of H+ and OH- in a solution. Buffers are typically composed of a weak acid and its corresponding base. Page 7  Created by Turbolearn AI Carbonic Acid-Bicarbonate Buffering System The carbonic acid-bicarbonate buffering system is an important buffer in human blood and many other biological solutions. It consists of: H2CO3 (acid) ⇌ HCO3- (base) + H+ (hydrogen ion) This system helps to regulate pH by: Releasing hydrogen ions when pH rises Removing hydrogen ions when pH drops Ocean Acidification 🌊 The absorption of CO2 by oceans has caused a decrease in pH, known as ocean acidification. This process alters the delicate balance of conditions for life in the oceans. CO2 Level pH Change Pre-industrial 0.1 pH unit higher than current levels Current 0.1 pH unit lower than pre-industrial levels Predicted by end of century 0.3-0.5 pH unit lower than current levels What is Ocean Acidification? Ocean acidification is the decrease in the pH level of the ocean due to the absorption of excess carbon dioxide (CO2) from the atmosphere. This increase in CO2 reacts with water to form carbonic acid, which releases hydrogen ions (H+) and reduces the concentration of carbonate ions (CO32-). Effects of Ocean Acidification on Coral Reefs Coral reefs are sensitive ecosystems that are affected by ocean acidification. The decrease in carbonate ion concentration makes it harder for corals to build their calcium carbonate (CaCO3) skeletons, which can lead to a decrease in coral growth and even coral bleaching. Scientific Skills Exercise: Interpreting a Scatter Plot with a Regression Line How Does the Carbonate Ion Concentration of Seawater Affect the Calcification Rate of a Coral Reef? Carbonate Ion Concentration (μmol/kg) Calcification Rate (mmol CaCO3/m²/day) 235 5 260 15 The linear regression line shows a positive relationship between carbonate ion concentration and calcification rate. This means that as the carbonate ion concentration increases, the calcification rate also increases. Questions and Answers What is shown on the x-axis? The x-axis represents the carbonate ion concentration in μmol/kg. Page 8  Created by Turbolearn AI What is on the y-axis? The y-axis represents the calcification rate in mmol CaCO3/m²/day. Which variable is the independent variable? The independent variable is the carbonate ion concentration. Which variable is the dependent variable? The dependent variable is the calcification rate. Calculations If the seawater carbonate ion concentration is 270 μmol/kg, estimate the rate of calcification and how many days it would take 1 square meter of reef to accumulate 30 mmol of calcium carbonate (CaCO3). If the seawater carbonate ion concentration is 250 μmol/kg, what is the approximate rate of calcification, and approximately how many days would it take 1 square meter of reef to accumulate 30 mmol of calcium carbonate? Acid-Base Chemistry and pH 🧬 What is pH? pH is a measure of the concentration of hydrogen ions (H+) in a solution. It is defined as the negative logarithm of the hydrogen ion concentration: pH = -log[H+]. Acid-Base Reactions A strong acid is a substance that completely dissociates in water to produce hydrogen ions (H+). For example, HCl is a strong acid that dissociates into H+ and Cl-. A base is a substance that accepts hydrogen ions (H+). For example, NaOH is a base that accepts H+ to form water and Na+. Buffer Solutions A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added. It consists of a weak acid and its conjugate base. Water Properties and Emergent Properties 🌊 What are Emergent Properties? Emergent properties are properties that arise from the interactions and organization of individual components, rather than being inherent in those components themselves. Properties of Water Cohesion: Water molecules are attracted to each other through hydrogen bonding, which gives water its high surface tension and ability to resist external forces. High Specific Heat: Water has a high specific heat capacity, which means it can absorb and release a lot of heat energy without a large change in temperature. Evaporative Cooling: Water has a high heat of vaporization, which means it can cool a surface through evaporation. Solvent Properties: Water is a polar molecule that can dissolve a wide range of substances, making it a versatile solvent. Review Questions 🤔 Multiple Choice Questions Page 9  Created by Turbolearn AI 1. Which of the following is a hydrophobic material? A. Paper B. Table salt C. Wax D. Sugar 2. What is the pH of a solution with a hydrogen ion concentration of 10^-4 M? A. 4 B. 6 C. 8 D. 10 Short Answer Questions 1. Describe how different types of solutes dissolve in water. 2. Explain what a solution is. Essay Questions 1. How do the emergent properties of water contribute to the suitability of the environment for life? 2. What do climate change and ocean acidification have in common? Page 10