1 How Substances Dissolve l Solids dissolve in

1

How Substances Dissolve l Solids dissolve in liquids at the surface l Water molecules are moving ¡ Polar l molecules Positive and negative areas l Solid molecules move ¡ Polar molecules l Same process for liquid with gas or melted solid with melted solid 2

Factors Affecting Reaction Rates l Most reactions go faster at higher temperatures ¡ Due to kinetic energy-hotter leads to faster particles ¡ Faster particles lead to higher energy which leads to more collisions l Example –potato slices cook faster at 2000 than 1000 3

4

Larger surface area speeds up reactions l More exposed area the faster the reaction ¡ Example – whole potato will take 30 minutes to cook ¡ Same potato sliced will take 10 minutes ¡ Solids-powder will dissolve quicker in solution than large block of material 5

Concentrated (stronger) solutions react faster l Small amount of solution will not be effective ¡ Bleach l Large amount of solution will be effective 6

Reactions are quicker at higher pressure -Higher pressure - more particles in lead to more collisions ¡ - Lower pressure comes - less particles lead to less collisions - - Quicker reactions Slower reactions Example – shake up a bottle of sodaincrease collisions which increase explosion when opened 7

Massive, bulky molecules react slower l The larger the molecule the slower it is l Some molecules need to collide on particular side for reaction to happen ¡ This takes many tries before large molecules react l Result – compounds react very slowly 8

Catalysts l Changes the rate of chemical reactions without being consumed l Speeds up or slows down reactions l Inhibitor-catalysts that slows reactions l Solid catalyst- usually speeds up reactions ¡ Catalytic converter on car ¡ More effective with large surface 9

Equilibrium Systems l The balance between a chemical reaction and its reverse occurring simultaneously ¡ Carbonated drink in closed container ¡ Burning, rusting and explosions are completed reactions l Can’t be reversed 10

l Some changes are reversible ¡ Carbonated drinks have CO 2 ¡ When the can is opened bubbles go into air and some back into drink 11

La Chatelier’s prinicple of equilibrium l. A change in chemical equilibrium leads to an equilibrium shift to a new equilibrium ¡ Change is caused by Temperature – l Pressure – l Concentrationl 12