Intro. to Physical Science
Exam
Zack Shevin
Lab Safety Notes
Goggles must be kept OVER YOUR EYES until Mr. Leeds says to put the away
Even if you are already finished and cleaned up
Report all accidents/spills to Mr. Leeds immediately
Try your best to use common sense
In case of Emergency
Nurse: ext: 2828
Safety equipment in classroom
Fire extinguisher
Fire blanket
Eye wash/shower
Chemical
Never taste chemicals
Always WAFT liquids to detect odor
NEVER WAFT SOLIDS/ POWDERS
Avoid touching chemicals
Always wash hands with soap and water after lab
If chemicals touch skin: flush skin with water for 1 minute AND notify Mr. LEeds
Glass
Hot and cold glass look the same
Never use chipped or broken glass
tell Mr. Leeds and dispose of broken glass in proper trash
Never use force to remove or insert glass
Alcohol Burners
Roll up sleeves, put UP long hair, NOT just pul back
Never walk away from a lit burner
Never point the open end of a hot test tube what yourself or someone else
Do not look down into a test tube while its being heated
Make sure burner is capped and flame is out when done
End of Experiment
CLEAN UP AREA AND MATERIALS COMPLETELY! (or you lose points)
Make certain that burner is out if one was used
Keep goggles on until Mr. Leeds says to put them away
1.1-1.3
Reaction in a Bag Post-Lab
Phenol Red
- used a pH indicator
- Below 7 turns yellow
- Above 7 turns pink
pH Scale
- Measures acidity
- Goes from 0-14
- 0-7-14
- acid- neutral- alkaline
- Lemon juice 1.5
- Tums 10
2 Solids
1. Calcium Chloride (A)
- acidic
- hydrotropic: attracted to water
- uses: canned veggies, electrolyte in sports drinks
- Flavors pickles
2. Sodium bicarbonate (Baking Soda) (B)
- non acidic
- uses: baking, laundry detergent
- Toothpaste
EXPERIMENTAL ERRORS:
- Hole in the bag: you would not know that a gas was produced
CHEMICAL REACTIONS:
A and Liquid = hot
B and liquid =cold
A + B + LIQUID = gas
Heating Baking soda post lab
Different substances because they look different. Something in tube 1 is not tea or baking soda.
Control group: Unheated Test Tube
Experimental group: Heated test tube
Indicator: Tea (shows solids are different)
Variable: Something you try to measure
Independent: causes change in dependent (Temperature)
Dependent: changes based on independent variable (tea color)
Control factors:
Same type of tea
Same amount of b soda
Same amount of tea
Same stirring time
Same size of test tube
Experimental Errors:
- Hole in tubing releases gas so bottle would not empty
- If stopper not snug, bottle won't empty
- Stirring rod not cleaned before lab, could contaminate
Extra Q
The condensation was less than the baking soda because the Baking soda made the condensation
Box Question 1:
The gas produced by baking soda makes batter rise
Volume Notes 1.2
- unit of meaurement = cm cubed
- volume= l x w x h
- Standard unit of length meter
- 1 cm = 0.01 m
- unit cube- 1cm X 1cm X 1cm
Volume of Liquids
ALWAYS check the intervals or scale
units- milliliters (mL) or cm cubed
Read from bottom of meniscus
Reading Scales
Single Pan Balance
- check that pan is clean and dry
- "zero" balance before using
- NEVER switch pans
1.4 - 1.8
1.4 Sand
Method used in lab- the displacement of water method
- Sand sticks to sides of wet cylinder the measurement would be off
- Pour water into sand (water sits on top of the sand because the air spaces do not allow the water to filter down
Extra question
- Why different amounts of sand for different groups
To prove that no matter how much sand you started with, the amount of air space in the sand was approximately 40%
Calculations
Volume of dry sand mixed with water - volume of water = volume of sand alone
volume of dry sand - volume of sand alone = volume of air space
volume of air / volume of dry sand = fraction of sand that is air
Note: when finding the volume of a powder like sugar that dissolves in water, use another liquid. With sugar you can use the displacement of vinegar method to find the volume.
Note: to find the volume of something with air space that floats like a cork, use another object to sink the cork down. The formula would then be the volume of the weight, water, and cork - the volume of the water- the volume of the weight = the volume of the cork.
1.5 Limitations of Volume as a Measure of matter
1.6 Mass
Equal Arm- Balance
- Developed in ancient Egypt
- Egyptians used rocks with units of beqa
Mass- standard unit is grams (g)
1 kilogram (kg) = 1000 grams (g)
1 kg= 2.2 lbs
Three types of balances-
- equal arm
- single pan
- electronic
1.7
Electronic is the quickest
Single Pan uses riders
Large objects cannot be measured easily on an Equal Arm
1.8 Sensitivity of a Balance
Experimental Errors-
1. Graphite on squares would make mass greater and mess up measurements
2. Cutting groups unevenly would throw measurements off
End Mass - initial mass = ∆M
∆M divided by # of yes on chart = the sensitivity of the balance
Change in Mass/ # of yes= sensitivity of the balance
Sensitivity of balance= the lightest mass you can expect the balance to detect
or the margin of error when massing something
Penny
- prior to 1982 penny 95% copper and 5% zinc
- after 1982 penny 2.5% copper and 97.5% zinc
- copper was needed in war to make shell casings for bullets
- a 1943 copper penny has been sold for $82,500
Chapter 2
2.1 Mass of Dissolved Salt
1. Not drying off cap
2. Removing cap before Mf
3. Cap not on tight
4. Spill salt when pouring into bottle
ALL RESULT IN DECREASES IN MASS!
If you have 2g of salt and dissolve it into a liquid, how would you get the salt back and how much salt could come back?
Letting the water evaporate would leave behind all 2g of the salt (we know this because it does not rain salt water)
Histograms (HEEEEESTOGRAMS)
Zero either on a line or in a space
Falls on a line ---> graph in box to the right of line
2.4 Ice Ice Baby Lab
Not wiping off condensation ---> gain in mass
Hand wet/ bottle wet during Mi ---> Lose mass
Shaking bottle ----> Some spills ----> Lose mass
Post Lab
CONDENSATION: forms when warm water vapor in the air (humidity) touches the cool surface of the test tube and becomes a liquid (was a gas before)
Condensation can form on outside or inside if there is no lid (only outside if sealed)
Restart lab if condensation forms on the inside
2.5- The Mass of Copper and Sulfur
Melting point of copper :1100 C
Melting Point of sulfur: 112 C
Yellow smoke ---> the water in the sulfur becomes a vapor and rises
when it cools-----> sulfur bonds with copper and forms copper sulphide
Errors:
1. Hole in sheet / sheet pops off / not sealed around top of tube
Gas escapes, Mf too low
2. Sulfur stick to inside of test tube- does not react to heat (no real effect)
2.6 Mass of a Gas
1. Water in pan during Mi --> Lose mass
2. Cap not on tight enough or quick enough ---> gas escapes --> lose mass
Alka-seltzer: antacid and pain reliever
contains aspirin, citric acid, and sodium bicarbonate (baking soda)
the baking soda produces the gas
2.7 Conservation of Mass
- Closed System - a space where nothing can enter or exit
- Groups could have had not ∆M because of the sensitivity of the balance
- All changes made in a closed system will not affect the mass
- called- THE LAW OF CONSERVATION OF MASS
2.8 LAWS OF NATURE
BQ 17: A student wished to add a new experiment. The mass of a beaker of water was 109.44g, after heating the beaker the mass was 109.08g . Does this contradict the law of conservation of mass?
NO because a beaker is an open container which allows the water to evaporate. It is not a closed system.
BQ 19: Why does "what goes up must come down" express a law of nature?
Yes, it explains the law of gravity. It is a law of nature that only applies to earth.
BQ 20: is "on a sunny day the sky is blue" a law of nature?
Yes because if the sky was looked at on a sunny day it would be blue. This only applies to earth because of the atmosphere
Chapter 3
3.1 Characteristic Properties
Property of a Substance: helps you identify what the object is made out of.
example:
Sharp, heavy, shiny, stainless-steel knife
Sharp: Object
Heavy: Object
Shiny: Object
Stainless-steel: Substance
Knife: Object
3.2 Mass and Volume
error: Cylinder wet during mass---> mass rises
Notes:
1. object that are made of the same substance that have the same volume, will have the same mass (regardless of their shape_
2. the mass of an object will double if its volume doubles
3. object that have the same volume but are made of different substances will not have the same mass (brass denser than aluminum)
3.3 Density
unit: g/cm3 (grams per cubic centimeter)
Density does not change with mass or volume and depends only on the substance
know graphs like ones to the right
3.5 The Density of a Solid
Can you tell which cube is denser just by holding?
Yes, same size, different weight
Can you tell whether the slab is denser just by holding?
No because you do not know the dimensions
CUBE 1 and SLAB SAME SUBSTANCE!
cube 2 different substance
The Rock
came from a bigger, sedimentary rock
Different densities because sedimentary rocks made up of different substances.
errors:
1. water splash- loss in volume and gain in density
2. Pain chipped off- loss in mass and loss in density
3. Measure same side of slab twice- change in volume
4. Find volume before mass of rock- the rock is wet during massing and mass increases causing density to also increase
3.6 Density of a Liquid
Errors:
1. Not remising empty cylinder
2. Outside of empty cylinder wet
3. Not rinsing out cylinder
Liquid B: Water
Liquid A: Water with Magnesium Sulfate
Magnesium Sulfate- sold under brand name epsom salt
3.7 The Density of a Gas
1. Foil not on Mf--> Mf Less---> Mass of a Gas more--->Density rises
2. Touching tablet after Mi--->Mass of Gas rises--->Density rises
3. Air bubble--> too much gas---> Volume rises---> Density falls
Gas Density should have been 1.8 X 10 to the power of -3 (because the tablet of alka-seltzer produces CARBON DIOXIDE