Page 7 - Physical chemistry understanding our chemical world

vi CONTENTS

What causes pressure? 30
Why is it unwise to incinerate an empty can of air freshener? 32
1.4 Further thoughts on energy 33
Why is the room warm? 33
What do we mean by ‘room temperature’? 34
Why do we get warmed-through in front of a fire, rather than just our
skins? 35

2 Introducing interactions and bonds 37
2.1 Physical and molecular interactions 37
What is ‘dry ice’? 37
How is ammonia liquefied? 38
Why does steam condense in a cold bathroom? 39
How does a liquid-crystal display work? 40
Why does dew form on a cool morning? 42
How is the three-dimensional structure maintained within the DNA double
helix? 44
How do we make liquid nitrogen? 47
Why is petrol a liquid at room temperature but butane is a gas? 49
2.2 Quantifying the interactions and their influence 50
How does mist form? 50
How do we liquefy petroleum gas? 52
Why is the molar volume of a gas not zero at 0 K? 54
2.3 Creating formal chemical bonds 59
Why is chlorine gas lethal yet sodium chloride is vital for life? 59
Why does a bicycle tyre get hot when inflated? 59
How does a fridge cooler work? 60
Why does steam warm up a cappuccino coffee? 61
Why does land become more fertile after a thunderstorm? 63
Why does a satellite need an inert coating? 64
Why does water have the formula H 2 O? 66
Why is petroleum gel so soft? 67
Why does salt form when sodium and chlorine react? 69
Why heat a neon lamp before it will generate light? 69
Why does lightning conduct through air? 72
Why is argon gas inert? 74
Why is silver iodide yellow? 75

3 Energy and the first law of thermodynamics 77
3.1 Introduction to thermodynamics: internal energy 77
Why does the mouth get cold when eating ice cream? 77
Whyisskin scaldedbysteam? 79
Whydowesweat? 81
Why do we still feel hot while sweating on a humid beach? 83