Science Exam Study Guide

Lab Saftey - Chapter 3 Section 8

Safty Notes


  • IPS Safety Notes

    For Every Lab

    · Goggles must be kept over eyes until instructed to by teacher

    · Report all accidents and spills to teacher immediately

    · Try your best to use common sense

    In Case of Emergency

    · Nurse extension 2828

    Safety Equipment in Classroom

    · Fire Extinguisher

    · Fire Blanket

    · Eyewash Shower

    Chemicals

    · Never taste

    · Always waft liquids to detect odor

    · Never waft solids or powders

    · Avoid touching chemicals

    · Always wash hands with soap and water after lab

    · If chemical touch skin – flush skin for one minute – notify teacher

    Glass

    · Hot glass and cold glass look the same

    · Never use chipped or broken glass

    o Tell the teacher and dispose broken glass in proper trash

    · Never use force to insert or remove glass

    Alcohol Burners

    · Roll up sleeves, put up long hair, not just pull back

    · Never walk away from a lit burner

    · Never point the open end of a hot test tube at yourself or someone else

    · Do not look down into a test tube or beaker when it is being heated

    · Make sure burner is capped and flame is out when done

    End of Experiment

    · Clean up area and materials completely or you will lose points

    · Make sure burner is out if used

    · Keep goggles on over eyes until teacher tells you to put away


Lab Reaction in a Bag

Red Liquid (Phenol Red)

· Uses as PH indicator

o PH Scale

§ Measures acidity

§ Goes from 0-14

· 0-6 = acid

· 7 = neutral

· 8-14 = alkaline

§ Lemon juice = 1.5

§ Tums = 10

o Below 7 turns yellow

o Above 8 turns pink

Two Solids

Solid A

o Calcium Chloride (calcium + chlorine)

o Acid

o Hydrotropic: attracted to salt (absorbs water)

o Uses

§ Canned veggies (keeps from getting spoiled)

§ Electrolyte

§ Flavored Pickles (salty)

Solid B

o Sodium bicarbonate (baking soda)

o Not acid

o Uses

§ Laundry detergent

§ Toothpaste

Chapter 1

1-1 Lab Heating Baking Soad

Part 1

· Condensation (moisture, foggy)

o Comes from hot gas touch cold air on top of surface of test tube

o Turns back into liquid

· Gas comes from baking soda

Part 2

· Are the two white powders the same substance? What is your evidence?

o No, the heated one is different because it is not the same color as the heated because the heated has baking soda in it

Lab Info

· Control Group = Unheated test tube

· Experimental Group = Heated test tube

o Indicator = Tea

§ Indicates that heated baking soda has changed

· Variable = something that you try to measure

o Independent variable = temperature or heat

o Dependent variable = color of Tea

o Control factors = factors we control

§ Same type of Tea

§ Same amount of baking soda

§ Same amount of Tea

§ Same stirring time

§ Same size test tube

· Experimental Errors

o Hole in tubing = won’t see bottle filled with gas

o Stopper not snug

o Won’t see bottle filled with gas

o Stirring rod not cleaned before you begin = contamination

· Extra Question

o Less (or equal to), because the condensation comes from the baking soda

It cannot produce more than itself

1-2 Volume

· Volume

o Unit of measurement: cm3 (cubic centimeters)

o Volume = length x width x height (a x b x c)

o Standard unit of length = meter (m)

o 1 centimeter /100

§ 1cm =.01 m

§ 100 cm = 1 m

· Unit Cube

o A small cube 1 cm on each edge

o One cubic cm (1 cm3 )

· Volume of Liquids

o Use a graduated cylinder to measure volume

§ *ALWAYS CHECK THE INTERVALS OR SCALE*

o Units = milliliters (ML) or cm3

§ 1 ml = 1 cm3

o Read from bottom of meniscus

1-3 Reading Skills

Single Pan Balance

· Check that the pan is clean and dry

· Always “zero” balance before each missing

o Push in all viders to zero “left”

o Use an adjustment knob

1-4 Lab Measuring Volume by Displacement of Water

Experimental Errors

  • · Sand sticks to the sides of wet cylinder

o Volume of sand and water would be too low

  • · Pour water into sand

o (water sits on top of sand because the airspaces don’t allow water to filter down)


Extra Questions

  • · It did not matter how much dry sand you had. The amount of air space was approximately 40%

1-6 Mass The Equil Arm Balance

  • · Beqa ancient standard mass used in Egypt
  • · Earliest balance found in Egypt (approx. 7,000 yrs. old)
  • · Mass Standard unit – grams (g)

o 1 kilogram (kg) = 1,000 grams

o 1 kilogram = 2.2 pounds (lbs)

1-8 The Sensitivity of a Balance

Penny Notes

  • · Before 1982

o 95% copper

o 5 % Zinc

  • · After 1982

o 2.5% copper

o 97.5% Zinc

  • · 1943

o Made up of steel and zinc

o Copper needed to shell casing bullets

o A 1943 copper penny sold for $82,500

  • · Mass of Penny

o Sensitivity of a Balance

§ The smallest change in mass that a balance can detect in a reproducible way

· + or – margin of error

Chapter 1 Test

*Look over chapter 1 box questions

  1. During the Heating Baking Soda experiment, a lab group does not realize that they have a hole in their rubber tubing. How will this affect there understanding of the lab. Answer: Do not know that when heating gas will escape.
  2. During the Reaction in a Bag Experiment, a lab group does not realize that there is a hole in there zip lock bag. How will this affect there understanding of the lab. Answer: Not know reaction produces a gas.
  3. For Measuring Volume by Displacement of Water Experiment, Mr. Leeds assigned groups different amounts of dry sand to begin the lab. Why did he do this. Answer: All groups get 40% of sand.
  4. In the sensitivity of a balance lab you where instructed to add 10 groups of squares with a mass between 0.003g and 0.007g to an already massed stopper. Why did they choose those range of mass for your ten groups of squares and not a smaller range? Answer: You would not have seen a change if they where that small.

Chapter 2

2-1 Lab The Mass of Dissolved Salt

  • · Salt dissolves in water

o Combined volume of salt + water decreases

  • · Subtract earlier value from later value

o = Change in mass

o Later mass greater than earlier one

o Positive sign indicates that mass increased

o Ex. 28.37 g – 28.36g = +0.01g

o Negative sign indicates that mass decreased

o Ex. 26.10 g – 26.12g = - 0.02g

o Changes can be positive, zero or negative


·

Experimental Errors

o Not drying off cap = Water in MI not therefore MF

o Remove cap before MF = Spillage/Leakage

o Not shaking long enough = not dissolved

o Cap not on tightly = spillage/leakage

o Spill salt when pouring into bottle = not enough salt


2-2 Histograms

  • · Change in mass

o Mass before dissolving from mass after dissolving

  • · Sensitivity of a balance is about 0.01 g greater than or less than what is reported

o Uncertainty is +-0.01 g

  • · Two measurements are subtracted to find the change in mass

o Uncertainty becomes +-0.02 g

o Calculating difference between two measurements doubles the uncertainty

  • · Picture with less detail ignores one small difference that could be within the uncertainty within the results
  • · If a value already appears – draw it’s square on top of one below it
  • · Height of each column tells of measurements
  • · Plot presents data by number of time
  • · Value appears in an interval called a histogram
  • · Try to set borders between intervals

o Results that occur most often fit into intervals rather than on borders

2-4 Lab The Mass of Ice and Water

  • · Ice melts – its volume decreases

Post Lab Notes:

  • · Condensation on bottle – comes from warm water vapor in the air
  • · Humidity – when it touches cool surface in bottle – it turns from gas to liquid
  • · Experimental Errors

o Not wiping off condensation = gaining mass

o Cap off/loose + water evaporates = lose mass

o Ice not completely melted = gain mass

o Bottle wet during MI = lose mass

o Shaking bottle = lose mass

2-5 Lab The Mass of Copper and Sulfer

  • · Dramatic change in matter takes place when sulfur and copper are heated together

Post Lab Notes:

  • · Melting point of copper = 1,100 o C (2,000o F)

o Too hot to melt in lab

  • · Melting point of sulfur = 112oC (235o F)

o Can melt in lab

o Gas was not sulfur (sulfur has too high of boiling point)

o Yellow smoke/gas is water in sulfur turning to vapor/gas

§ Yellow from sulfur dust

o When cooled down sulfur bonds with the copper = copper sulfide

  • · Class saw change in mass (but no change if factor in sensitivity of balance)

o 50%

· Experimental Errors

o Hole in rubber sheet = gas could escape

o Sheet pops off = gas could escape

o Rubber band not tight enough = gas could escape

o Not sealed around top of test tube = gas could escape

§ Decrease in mass if gas escapes

o Will not affect lab if you spill copper or sulfur

§ Does not matter until test tube sealed

o Sulfur sticks to side of test tube = doesn’t react

o Cleaning lab/pan

2-6 Lab the Mass of a Gas

  • Alla-Seltzer: antacid and pain reliever
  • aspirin and citric acid and baking soda
  • produce gas

Errors:

  • Water in pan during MI
  • Cap is wet during MI
  • Touch tablet after MI
  • Cap is not tight or quicken on


2-7 The Conservation of Mass

  • · Closed System – an experimental set up in which nothing added or lost

o Most changes observed are zero or close to zero

o Results indicated that no change in mass that could be measured

  • · Changes that take place in closed system – Mass in conserved

o Remains exactly the same

  • · The Law of Conservation of Mass

o Checked in many experiments to one part in a billion for a large variety of changes

o Does not prove it would hold forever under all conditions

o Great deal of confidence in the law

  • · Volume convenient way to measure the amount of matter

o Matter changes form

o May have change in volume but no observable change in mass

o Unlike volume – mass is conserved

2-8 The Laws of Nature

      • · Law of Conservation of Mass is first of several laws of nature
      • · Laws of Society are different than the Laws of Nature
      • · Laws of nature are generalizations that begin a lucky with a lucky guesses based on few crude experiments

      o Started with consistent descriptions of patterns in nature or generalizations based on analysis of many careful conducted experiments

      • · Present convincing evidence that law not quite true

      § Law changed to take new data into account

      § Change is recognized that law has limits

Chapter 2 Test

* Look over Chapter 2 box questions
  • Describe a possible error discussed in class, which could lead to a loss in mass during the Mass of a Gas lab. Answer: Error: Putting the Alta-Seltzer tablet into the bottle some water could have splashed out. Explanation: You will lose mass because some of the water that was put into the bottle at the beginning of the lab will be gone when the table in pleased into the bottle
  • Describe a possible error discussed in class, which could lead to a loss in mass during the Mass of copper and Surfer lab. Answer: Error: Rubber sheet is loose. Explanation: gas will come out of bottle
  • During an experiment of Ice and Water, a gain in mass is noted by a lab group. Give an error that will gain mass. Answer: Error: Not wiping of condensation after Mi. Explanation: Will gain mass because of extra water in the cylinder.


Chapter 3

3-1 Properties of Substances and Objects

  • Property of an Object: does not tell you what it is made of.
  • Property of a Substance: this helps you to identify what the object is made out of.

3-2 Lab Mass and Volume

Errors:


  • When the cylinder is wet after taking volume then it will add mass

Notes


  • Objects that are made of the same substance that have the same volume, will have the same mass. (regardless of their shape) Example: short and long aluminum cylinders
  • 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. Example small brass and aluminum cylinders

3-3 Density

  • a characteristic property
  • is specific to liquids, solids and gases
  • can help ti identify substances
  • Density = Mass/Volume or D=M/V
  • Aluminum: 2.7g/1.0 cm3 (can't do exponents on Smore) =2.7 g/cm3
  • Brass: 8.5g/1.0cm3=8.5 g/cm3


The Rock

  • Lab groups get different density calculations for their rocks because they all have different densities because the rock is formed by many substances being compressed together.
  • Different substances = different densities

3-5 Lab The Density of a Solid

  • Histogram shows that Cube 1 and Slab are most likely same substances. Cube 2 is a different substance.
  • M/V
  • If V is the same
  • Object with greater mass and greater density

Errors:

  • Find V of Rock before mass
  • rocke wet from earlier class
  • Water splashes out of graduated clindar
  • Measure same side twice
  • first 4 = M increase/V + D increase
  • Paint chips off object = mass decrease


3-6 Lab the Density of a Liquid

Errors


  • Not wiping off water in outside cylinder (empty)
  • Not rinsing out cylinder between substances
  • Not re-massing cylinder empty

Notes

  • Magnesium sulfate: Epsom Salt


3-7 Lab The Density of a Gas

Blue Dot Questions


  • Water leaves the bottle because it is denser than the air
  • Represents the water not displaced by the gas
  • Gas s in the tablet for MI, but it has left for MF


Notes

  • Gas is Carbon Dioxide (C02)
  • D= 1.8 x 10-3 g/cm3

Errors

  • Spill water when measuring volume of bottle
  • Not putting foil on MF
  • Don't touch Alka Seltzer after MI
  • Air bubbles in bottle

Chapter 3 Test

* Look over Chapter 3 box questions up to 3.8
  • To calculate density we found both the mass and the volume of the liquid in the graduated cylinder because it is the most accurate method and we do not have to transfer liquid.
  • During the Density of a gas lab the rubber tubing is incorrectly inserted near the bottom of the bottle which will cause less gas to collect in the bottle.
  • In calculating the density of a rock, it would be an experimental error to find the volume prior to massing.
  • When the alka-seltzer tablet is mixed with water, sodium bicarbonate within the tablet releases carbon diode
  • In the density of a gas lab a student forgets to include the foil for the MF the result in mass of gas increase density decrease
  • Epsom salt is the marketing name for Magnesium sulfate