Exam Study Guide

By: Emily Smith

Lab Safety

For Every Lab:



  • goggles over eyes until directed to take them off (even if finished)
  • report all accidents/ spills to Mr. Leeds immediately
  • try to use common sense
In case of emergency:



  • 2828


Safety equipment in classroom:


  • fire extinguisher
  • fire blanket
  • eye wash/ shower


Chemicals:


  • never taste
  • never touch
  • always waft liquids
  • never waft solids/ powders
  • wash hands with soap and water after lab
  • if chemicals on skin: flush skin with water for a minute and tell Mr. Leeds


Glass:


  • hot and cold glass look the same
  • never use chipped/ broken glass (tell mr. leeds and dispose correctly)
  • never use force to insert or remove glass


Alcohol Burners:


  • roll up sleeves; tie up hair
  • never walk away from lit burner
  • never point open end of test tube at yourself or someone else
  • don't look down into heated beaker/ test tube
  • make sure burner is capped and flame is out when done


End of Experiment:


  • clean up area and materials (or points lost)
  • make sure burner is out
  • keep goggles on eyes until otherwise directed


Measurements

volume: lwh

volume of sand alone: sand/water- water

volume of air space: dry sand- sand alone

volume of water that fills the air spaces in the dry sand: airspace

volume of water that does not fill the air spaces in the sand: volume of water- airspace

1kg: 2.2 pounds

sensitivity of balance: end-beg.=change in mass/#'s of y's

volume: cubic centimeters

percentage change in mass of the reacting substances: change in mass/ Mass initial= x/100

density= m/v

1kg= 1000g

standard unit of length: meter

1 centimeter: 0.01 meter

100cm: 1m

1mL: 1cubic centimeter

change in mass/ #of y's= sensitivity

density= g/cubic centimeters

Exp. Errors

rubber tubing not inserted correctly near the bottom: less gas to collect in the bottle

less gas in bottle: volume decrease> density increase

foil not included in Mf- mass of has increases, density increases

sand sticks to side of the wet cylinder: v of sand+water would be too low

tubing must be at the top of the bottle or volume will decrease and the density will increase

Vocab

Observation- information obtained by the senses- often by direct measurement.


Inference- a conclusion based upon known observations.


Hypothesis- A proposed solution to a scientific problem.


Control Group- the group that is the standard for comparison in any experiment.


Experimental Group- the group receiving the variable being tested. Control Factors- the variables that are held constant. They are the same for both the control group and the experimental group.


Indicator- a substance used to show the presence of another substance.


Volume- the amount of space something occupies. True of solids, liquids, and gases.


Volume Displacement Technique- quick and easy way to determine the volume of a solid or gas.


Mass- the amount of matter in a substance (true of solids, liquids, and gases)


Meniscus- the curved portion of a liquid when in a container. Must read the bottom of the meniscus- at eye level- for proper measurement.


Characteristic Properties- Properties that show differences between substances. Examples: density, boiling point, solubility, melting point.



Density- Mass per unit volume of any substance. Unit of measure is

g/cm3.


Sensitivity of Balance- the lightest mass that balance can detect

Other

Pennies:

- before 82: copper/ zinc

- after 82: copper, zinc

Law of Conservation of Mass

- in a closed system, mass will remain constant, regardless of the actions of the processes inside the closed system

Chemicals

when alka seltzer is mixed with water, sodium bicarbonate releases carbon dioxide

Epsom salt: magnesium sulfate

calcium chloride: calcium+chlorine, hydrotropic, mildly acidic

sodium bicarbonate: baking soda