Exam
By Alexis Adornato
Reaction in a bag
- Red Liquid=Phenol Red
- Solid A=Calcium Chloride
- Solid B=Sodium Bicarbonate
Experimental Errors
- Hole in the bag-you would not know a gas in produced
Heating Baking Soda
- Condensation comes from hot gas touching cooler top of test tube turns it back into a liquid
- Control Group-what we can control (unheated)
- Experimental group-(heated)
- Indicator-(Tea)
- Variable-something you try to measure
- Independant Varible-causes a change in dependant variable
- Control Factors- Same type of tea, same amount of tea, same amount of baking soda, same temperature, same stirring time, same size test tube
Experimental Errors
- Hole in the tubing=won't see the bottle fill with gas
- Stopper not snug=gas leaked out
- Stirring rod is not clean at the beginning
Volume Notes
- unit of measurement: cm3
- Volume=lwh
- Standard Unit of Length=meter
- 1 centimeter= 0.01 M
- 100=1m
- use a graduated cylinder to measure volume
- Always ch4eck the intervals or scale
- Units-millileters (ml) or cm3
- 1ml=1cm3
- Read from the bottom of the meniscus
Single Pan balance notes
- check that pan is clean and dry
- Always zero balance before each massing
- Never switch pans
- Pick up balance by red bar only
- Dont zero balance when done
Measuring Volume by Displacement of Water
- sand sticks to the sides of the wet cylinder
- Pour water into sand (sand sits on top of the sand because the air spaces don't allow water to filter down)
Extra Question
Why were lab groups instructed to use different amount of sand?
It didn't matter how much dry sand you had that amount of air space was approximately 40%.
Mass Notes
1 Kilogram=1,000 g
1KG=2.2 lbs
Sensitivity of a Balance
- if you cut the wrong amount of squares down or across
Penny Notes
After 1982-97.5% Zinc 2.5% copper
1943
-made of steel and zinc
-copper was needed for shell casings
-a 1943 copper penny has sold for 82,500
Mass of Dissolved Salt
- not drying of the cap
- removing cap before mf
- not shaking long enough
- cap not on tightly
- spill salt when pouring into bottle
Ice Ice Baby
Experimental Errors
- not wiping off condensation-gains mass
- cap not sealed, water evaporation-lose mass
- ice not fully melted
- bottle is wet during mi-lose mass
- shaking bottle-lose mass
Mass of Copper and Sulfur
Melting point of Sulfur-112 C=235 F
Yellow Smoke-water in sulfur turns to vapo and rises in the test tube
When it cools-sulfur bands with copper and forms copper sulphide
Experimental Errors
- a hole in the rubber sheet-gas escape (lose mass)
- Rubber band not on test tube tightly-sheet pops off (lose mass)
- sulfur sticks to sides of the test tube-no reaction
Mass of a Gas
- cap wasn't on tight-lose mass
- dont close cap fast enough-lose mass
- cap is wet during mi-lose mass
- water in pan during mi-lose mass
- touch tablet after mi-lose mass
Alka Seltzer-Anti Acid pain reliever
Bicarbonate produces gas
Closed System-airspace where nothing can enter or leave
Law of Conservation of Mass
Vocab
Property of a substance: This helps you to identify what the object is made out of
Mass and Volume
- mix up cylinders
- Cylinders are wet when massing-gain mass
- water splashes out of cylinder-lose volume
Mass and Volume Notes
- Objects that are madd of the same substance and that have the same volume will have the same mass regardless of their shape
- The mass of an object will double if its volume doubles
- Objects that have the same volume but are made of different substances will not have the same mass
Density
-is specific to liquids, solids
can help to identify substances
D=M
V
Density of a Solid
Experimental Errors
- V before M-gain mass
- Rock wet from earlier-gain mass
- Water splashes out of the graduated cylinder
- measure some side twice
- paint chips off object-lose mass
Density of a Liquid
- not wiping off water on the outside of the cylinder
- not rinsing the cylinder between substances
- not remassing the cylinder empty
Magnesium Sulfate-Liquid A-Epsom Salt
Water-Liquid B
Density of a Gas
- spilling water when measuring the volume
- touching the tablet after mi
- massing the mf without the foil