ch 5 - Chapter 5 The Water We Drink Question What single...

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Chapter 5 The Water We Drink Question • What single advance has led to more than 80% of the increase in human longevity since the turn of the 19th century? Ability to provide clean fresh water. • Why? Before unknown diseases from sewage in the water source Introduction – What is so special about water? – Why is water so important to life? – Why do some things never freeze? Inner molecular forces – How does water dissolve substances? What are the consequences? And how do we minimize the negative effects of dissolution? Introduction to Properties • Ignoring other factors, substances of similar molecular weights tend to have similar properties with respect to solids, liquids, and gases • Except for water. Water’s Unusual Properties • What if our earth, our air, did not have so much water? Humidity- more humidity in heat, will sweat and drain yourself faster than low humidity • What if our atmosphere consisted of different substances? • What if our bodies used another material than water? • Many, many things would have to be different. Properties of Other Substances Substance       Spec heat / heat of fusion / heat of vaporization Nitrogen         2.0 J/ ° C/g  26 J/g  200 J/g Ethane         1.7 J/ ° C/g  95 J/g  490 J/g Ethyl alcohol   2.4 J/ ° C/g  100 J/g  945 J/g H 2 O        4.2 J/ ° C/g  331 J/g  2250 J/g Heat of fusion – heat needed to melt 1g of a substance Heat liquid needs to give off in order to freeze (oranges and igloos) Heat of vaporization- the heat that a liquid needs in order to become a gas(vapor) Same number of heat gas needs to give off to become a liquid Your Turn • Compare the heat required to change the
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temperature of 1000g of water and ethanol from 25 o C to 75 o C. Compare the time it would take using a stove that produced 1 kW of power. • Compare the amount of heat required to boil equal masses of all of the liquids on the previous slide. Why? • Why is water so unusual? 3 Molecular Shape • H 2 O – Electronic geometry: tetrahedral – Molecular geometry: angular or bent • This matters! Electronegativity Electronegativity • Electronegativity differences between two atoms in a bond suggest bond type. – Rules of thumb (
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This note was uploaded on 03/19/2008 for the course CH 305 taught by Professor Sutcliffe during the Spring '08 term at University of Texas.

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ch 5 - Chapter 5 The Water We Drink Question What single...

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