Unique Properties of Water PDF

# Properties of Water ## Learning Goals - You will be able to describe the structure of water. - You will be able to identify the properties of water. - You will be able to describe how these properties of water are essential for sustaining life on Earth. ## Water's Structure - Water is a molecu...

# Properties of Water ## Learning Goals - You will be able to describe the structure of water. - You will be able to identify the properties of water. - You will be able to describe how these properties of water are essential for sustaining life on Earth. ## Water's Structure - Water is a molecule made of two hydrogen atoms and one oxygen atom. - The Hydrogen atoms have a slightly positive charge and the Oxygen atoms have a slightly negative charge. ## Polarity - Polar Molecule = a molecule that has one side that is more negative than the other. - The Oxygen atom is more negative than the Hydrogen atoms. ## Press Pause, Think & Share 1. Think about the following... - What are the atoms that make up a water molecule? - Which type of bonds hold the atoms together? - What does polarity mean? 2. Post your thoughts in Today's Meet. ## What Did You Discuss? - What are the atoms that make up a water molecule - 1 Oxygen atom and 2 Hydrogen atoms - Which type of bonds hold the atoms together - Covalent bond because the atoms share electrons - What does polarity mean? - Polar Molecule = a molecule that has one side that is more negative than the other. ## Properties of Water - Polar molecule - Cohesion and Adhesion - High specific heat - Density - greatest at 4°C (AKA water floats) - Universal solvent - Neutral pH ## Water Has A Variety of Unusual Properties Because of Attractions Between These Polar Molecules - The slightly negative regions of one molecule are attracted to the slightly positive regions of nearby molecules, forming a hydrogen bond. - Each water molecule can form hydrogen bonds with up to four neighbors. ## Hydrogen Bonds - Hold water molecules together - The hydrogen bonds joining water molecules are weak, about 1/20th as strong as covalent bonds. - They form, break, and reform with great frequency - Extraordinary Properties that are a result of hydrogen bonds - Cohesive behavior - Resists changes in temperature - High heat of vaporization - Expands when it freezes - Versatile solvent ## Organisms Depend on Cohesion - Hydrogen bonds hold the substance together, a phenomenon called cohesion. - Cohesion is responsible for the transport of the water column in plants - Why is this important? - Cohesion among water molecules plays a key role in the transport of water against gravity in plants. - Adhesion, clinging of one substance to another, contributes too, as water adheres to the wall of the vessels. ## Surface Tension - Surface tension, a measure of the force necessary to stretch or break the surface of a liquid, is related to cohesion. - Water has a greater surface tension than most other liquids because hydrogen bonds among surface water molecules resist stretching or breaking the surface. - Some animals can stand, walk, or run on water without breaking the surface. ## Moderate Temperatures on Earth - Temperature is the measurement of the movement of atoms/molecules. - As water temperatures increase, hydrogen bonds begin to break. - As water temperatures cool, hydrogen bonds form more readily. ## Specific Heat - Specific Heat is the amount of heat that must be absorbed or lost for one gram of a substance to change its temperature by 1°C. - Why is this important? 1. Prevention of temperature changes that are outside the range suitable for life. 2. Coastal areas having a mild climate ## Evaporative Cooling - The cooling of a surface occurs when the liquid evaporates - This is responsible for: - Moderating earth's climate - Stabilizes temperature in aquatic ecosystems - Preventing organisms from overheating ## Density of Water - Most dense at 4°C - Contracts until 4°C - Expands from 4°C to 0°C - Why is this important? 1. Prevents lakes from totally freezing so aquatic organisms can live 2. Ice forms on the surface first - the freezing of the water releases heat to the water below creating insulation. 3. Acts as hunting grounds for some organisms ## Universal Solvent - Because of water's polarity many compounds dissolve in water - Why is this important - Most biochemical reactions involve solutes dissolved in water - we need to get stuff in our cells! ## Neutral pH - pH Scale - Measures the degree of acidity (0 - 14) - Water has a pH around 7 - Why is this important? - Most biological functions take place in a neutral pH. ## Press Pause, Think & Share 1. Think about the following... - Name as many properties of water as you can (Hint: There are 6) 2. Post your thoughts in Today's Meet. ## What Did You Discuss? - What are the properties of water? - Polar molecule - Cohesion and Adhesion - High specific heat - Density - greatest at 4°C - Universal solvent - Neutral pH ## In OneNote Make A Table That Has One Column With The Properties Of Water And Another With Why These Properties Are Important | Properties of Water | Why these properties are important to life | | ------------- | ------------- | | | | | | | | | | | | | | | | | | |