demo time decomposition of hydrogen peroxide ki 2h 2 o 2 2h 2 o + o 2 + heat!
TRANSCRIPT
Demo Time
Decomposition of Hydrogen Peroxide
KI
2H2O2 2H2O + O2 + HEAT!
Follow Up Questions
Answer on a sheet of notebook paper:1. Describe what happened in this
demonstration.2. Was this an endothermic or
exothermic reaction?3. What was the catalyst in this
reaction? 4. What 2 products caused the
dramatic “smoke”?5. What type of reaction is this? Synthesis, decomposition or replacement
Precipitate Reactions
If the ions in 2 solutions combine to form a solid and that solid is NOT soluble with the solvent produced a precipitate will form.
Example
Fe(NO3)3(aq) + 3 NaOH(aq) Fe(OH)3(s) + 3 NaNO3(aq)
Demo Time
Cu(NO3)2(aq) + 2 NaOH(aq) Cu(OH)2(s) + 2 NaNO3(aq)
Follow Up Questions
Answer on a sheet of notebook paper:
1. Describe what happened in this demonstration.
2. What is a precipitate? 3. What type of reaction is
this? Synthesis, decomposition or
replacement
Balancing Equations
All atoms of reactants must be account for after the reaction!
Acids
Produce H+ ions in H2O
Ex: HCl H+ + Cl-
Properties:•Tastes sour• Corrosive reaction w/metal
• Reacts w/CO32- to make CO2
• Turns blue litmus paper red
Examples of Acids
• HCl – hydrochloric acid
• CH3CO2H – acetic acid (vinegar)
• H2SO4 – sulfuric acid
• Ascorbic Acid – Vitamin C (citrus)• Fertilizers – Nitric & Phosphoric Acid• Lactic Acid
Bases
Produce OH- ions in H2O
Ex: NH3 + H2O NH4+ + OH-
•Tastes bitter• feels slippery• Turns red litmus paper blue
Examples of Bases
• NaHCO3 – baking soda
• household cleaners including:
• NH3- ammonia
• Drain Cleaner
Strength
The strength of an acid or a base is based on how well it produces ions in water.
Strong Acids – HCl & H2SO4
Strong Bases - NaOH
Measuring Strength
pH = Potential Hydrogen
Range of values from 0 to 14 that describes the concentration of H+
ions in a substance.
Safety
Know the pH (strength) of the acid or base you are handling.
Everything from 2-12 is in the safe zone.
PrecautionsWhen working with a strong acid or base (0-2 or 11-14) be sure to wear goggles…even if it’s a dilute solution!
For spills-Pour vinegar on a base & sodium bicarbonate on an acid…because…
Acid Base Neutralization
Displacement reaction
Acid + Base (liquid) water +(solid) salt
Salt = Group 1-2 Metal + a halogen
Demo Time
NaHCO3 + NaOH Na2CO3 + H2O
Chemicals Everywhere
Chemistry all around us:•Beauty products•Cleaning products•Food products•Scents & flavors•Monitoring the environment•Containers•Protection •Explosives
Materials
We use the following materials on a regular basis, they are made of various substances that we’ve been studying lately:•Plastics•Metals•Alloys•Ceramics•Glass
Chemistry Around Us
• Beauty products• Cleaning products• Food products• Scents & flavors• Monitoring the environment• Containers• Protection • Explosives• Fuels
Polymers
Large complex molecules made from smaller molecules joined together in a repeating pattern (chain).
They are both naturally occurring & synthetic.
Forming Polymers
Carbon Structures
Polymers are mainly composed of various configurations of Carbon (C) & Hydrogen (H)
Natural Polymers
• Cellulose – cell walls of fruits & vegetables
• Starches – pasta, bread & vegetables
• Natural fibers – hair, wool• Amino Acids Protein
DNA!
Synthetic Polymers
• Plastics MANY types (see p.731)• Fibers – carpets, nylon• Chewing gum• Teflon coating
Plastics
Benefits:• Cheap & easy to make• Lightweight• Versatile• DurableProblems:• Disposal Recycling is cost prohibitive
Alloys
A mixture of 2 or more elements at least one of which is a metal.
Alloys are usually stronger & more durable than the metals which they are made from. They are also less likely to suffer corrosion from oxidation.
Examples
• Sterling silver – Ag & Cu• Gold – Au &/or Cu• Pewter – Sn, Sb, Cu, Pb*• Brass – Cu, Zn• Steel – Fe, Cr, Ni, C
Ceramics
Hard, crystalline solids made from heating clay (water & minerals – Si, AL & O) to very high temperatures.
Properties
• Water resistant• Strong building material -
bricks• Not conductive of electricity• Can withstand much higher
temperatures than most metals
• Brittle & prone to breaking
Uses
• Containers • Storage• Cookware• Archaeologists use ceramic
sherds for relative dating!• Home construction – roofs &
floors• Replace joints – hips, knees,
teeth (dentures)
Glass
Molten sand & limestone can be shaped and cooled into waterproof vessels.
Uses
• Storage• Containers• Windows• Lenses for eyeglasses,
telescopes, microscopes• Cookware• Data transmission (optical
fiber)