Name 1 ______________________________
Name 2_____________ ______________________
GEOS 110 – Fall 2015 - Lab 2: Introduction to Properties of Gases and Liquids
This lab has several parts, including this “hands-on” part which deals with properties of fluids – gases
to represent the atmosphere, and water to represent the ocean. Demonstration with Liquid N2 as
available. e.g. density, surface tension and momentum of liquid versus gas form, crystallization of
oxygen, reversible balloon etc.
1. Gases
The aim here is to investigate some of the properties of gases, using simple equipment.
Materials
Large balloons , Fine thread, meter stick, 1-L beaker, three 50- or 100-mL beakers, 125-mL
Erlenmeyer flasks, ring stand, clamp, wire gauze, ring, empty soft drink bottle, 2 drinking glasses ,
empty pop cans, pieces of cardboard, index cards or wax paper, clean plastic bottle with lid, empty
aluminum soft drink can, bottle of perfume, 100 mL concentrated ammonia, NH3
(aq)phenolphthalein, 10 mL concentrated hydrochloric acid, HCl (aq), iodine crystals, printer paper, 2
petri dishes, clear, empty wine bottle, tightfitting cork, rubber hoses, hair dryer guns (hand held),
paper matches, small plastic (lightweight) balls
Part 1. Is air really matter? Does it have mass and occupy space?
1. Weight is the force on an object due to gravity. W=mg Demo: We’ll balance two ~equally filled
balloons by hanging them from a meter-stick balance. Note the direction of the balance’s tilt after we
pop one balloon. What happens and what does this demonstrate?
(2)
2. Lower an “empty” glass, open end downward, into a larger beaker (or pot) of water. Does water
fill up the “empty” glass? Tilt the glass.
(2)
What happens and what does this demonstrate?
Part 2. What is air pressure all about?
3. Select a balloon that is easy to blow up. Insert the bottom of the balloon partway into an empty
soft drink bottle, stretching its neck over the bottle mouth. Blow up the balloon so it fills the
container. (2)
What happens and explain the result?
4a. Place 10 mL of water in a 125-mL Erlenmeyer flask. Place the flask on a hot plate and bring the
water to boiling. Do not boil the flask dry. Remove the flask from the source of heat and quickly
and carefully place an empty balloon over the mouth of the flask. (It helps to pre-stretch & blow up
the balloon once before it is used.) Record what happens and explain the result.
(2)
1
4b. Blow up some balloons and draw a picture or write your name on the side with a magic marker
pen. Note the size of the inflated balloon and or your picture or word. Lay the balloon either on a tray
with ice in it to cool the gas in the balloon or on a tray and pour some liquid nitrogen over it. Describe
what happens to the balloon as it cools. Explain why this happened. Once the liquid nitrogen boils
off, what happens to your balloon? Why did this happen?
(4)
Air exerts pressure upward and in all directions. Fill a clear plastic glass with a flat rim, to the rim
with water, then cover it with either heavy wax paper, flat stiff plastic or shiny flat shirt cardboard.
Press down along the edges to make a tight seal, turn the glass upside down over a sink, and let go of
the cover. It may take a few attempts, but it is possible to have the water supported without the water
coming out. Note that: water has an approximate density of 1.00 g/mL, 1 atmosphere=760 mmHg or
101,325Pa (1Pa = 1N/m2), g=980 cm/s2 (9.8 m/s2). One Newton is the force required to accelerate a
mass of one kilogram at a rate of one metre per second squared: F = ma, m (kg) by a (m/s2). A column
of the atmosphere one square centimeter in cross-section, at sea level, has a mass of about a kilogram
and a weight (force) of about 9.8 N (9.8 kg m/ s2).
5a. Two forces acting on the index card; one pushes up and one pushes down (see the
arrows in the above diagram). What is producing the force that is pushing down on the
card? You can calculate the mass of water as its Density (g/mL)xVolume (mL) = mass (g).
Next use F=ma to calculate the net downwards force.
(2)
5b. What producing the force that is pushing up on the card? (Hint: what substance is under
the card?) Name the force: ______________________________________________ (1)
5c. Which force is greater? How do you know? (Hint: Go read the barometer on the front desk!
The scale in 29.x-30.x is inches of mercury. The scale in fractions close to 1.00 is atmospheres.
1 atm = 1.013 bar in cgs units) Name the greater force: ____________________________ (1)
Give the value and units of the greater force. ____________________________________ (1)
2
6. Consider varying the size of the cup and amount of water it can hold. For simplicity,
consider your cup to be a tube, hose or cylinder, so that it’s Volume = h x πr2 and its Mass =
Density x Volume. Assume its Density = 1.000 g/mL. Use the info above to answer:
a. If the cup were 30 cm tall, would this still work? ________________________________ (1)
b. What about 300 cm? ________________________________________________________ (1)
c. What about 3000 cm? _______________________________________________________ (1)
7a. Repeat the process in (5) above, without filling the glass completely. Now put the card
over it and invert it over the sink. Explain what happens and why? Hint is the weight of
water in the cup greater or less than before? _________________________________________
________________________________________________________________________________
_____________________________________________________________________________ (2)
b. In your mind, turn your partly filled glass into a hose with some air on the top and your
thumb over the open end and water inside down to the end of the hose. Calculate how long
a length of water in the hose you can have on Earth at sea level and not have the water
spontaneously drain under its own weight? Explain what happens and why? Hint is the
weight of water in the cup greater or less than before? _______________________________
________________________________________________________________________________
________________________________________________________________________________
_____________________________________________________________________________ (3)
Part 3. Diffusion of gases – Demonstration and Atmospheric Pollution and Transport.
Materials: A very strong perfume or (2-isobutyl-3-methoxypyrazine...C9H14N2O is detectable
at 0.002 ppb (= 2 ppt); Mercaptan = methanethiol is also detectable as low as 0.02 ppb but
smells much worse as in a porta-potty on a hot summer day! Methyl salicylate (oil of
wintergreen, C6H4(HO)COOCH3) is detectable at 40 ppb. Place an open dish on an overhead projector in the SE corner of F300 with the hood in the opposite NW corner turned on.
For other “smelly” organic chemical look up their odour thresholds or see:
http://www.leffingwell.com/odorthre.htm
8. Diffusion of gases. At the back corner of the classroom, we’ll open a bottle of with safe, odoriferous
substance with high vapor pressure. Raise your hand as soon as the odor is detected. What does this
demonstrate about the motion of gas molecules for direction and speed? ________________________
_______________________________________________________________________________ (2)
3
9. Demonstration on diffusion rates of gases. Diffusion is how one molecule or atom moves
through a mass of unlike ones. We’ll place two small beakers (one container has ammoniawater, the other initially has pure neutral water with phenolphthalein, a base indicator that
turns from invisible in neutral pH solutions to pink in the presence of hydroxyl OH- ions)
under a large sealed plastic or glass container on top of an illuminated (warm) overhead
projector. Do not allow ammonia fumes to escape as they are irritating and smell like a
diaper pail! In the equation below, the double arrow denotes equilibrium and what is going
on in the basic ammonia water solution. Moving to the right means ammonia gas escapes to
the air. Moving to the left means ammonia gas from the air dissolves to form an ammonium
hydroxide aqueous solution. The subscripts are: l – liquid, g – gas and aq – aqueous
(dissolved in solution) referring to the physical state of each molecule or ion.
Note: (NH4)+ aq + (OH -) aq   NH3 g + H2O l
Placing the experiment on an overhead projector makes it more visible, and the heat causes
the gas to have a higher partial (vapour) pressure so the ammonium ion in solution reduces
to ammonia gas and vaporizes and diffusion speeds up. Draw and label or describe what
you see. Clearly label which dish is which and not the colour change and its specific
location.
(6)
8.
We’ll perform a similar demonstration using solution of hydrochloric acid solution
(which evolves some hydrogen chloride vapour molecules) and ammonia water (the basic
solution from experiment 11, to produce solid ammonium chloride (it’s a nifty reaction).
HCl g + NH4OH aq   NH4Cl s + H2O l
Here the 2 dishes are represented by the left side and the air in the box is on the right.
During the experiment, HCl g comes off one dish and the NH3 g comes off the other dish and
the unlike gases collide in the air of the container to precipitate solid ammonium chloride
particles and condensed microscopic droplets of water from the steam produced by the acidbase neutralization reaction. As above, draw and label or describe what you see. Clearly
label which dish is which and not the colour change and its specific location.
(6)
4
9. One way to “clean-up” ground water contaminated by organic solvents like gasoline is to
spray the water into the air then collect the purified runoff water for reinjection back into the
aquifer. In hot arid areas, salt ponds or saline ground water can be sprayed into the air to
separate the salt which precipitates out as the steam blows away in the low relative
humidity. In our cities and industrial sites, we routinely use smokestacks to disperse
combustion products from oil and coal such as: uncombusted light hydrocarbons (benzene
C6H6), CO2 , SOx , NOx , C soot and fly ash. Comment on the transport agent and
environmental fate of volatile chemical compounds, gases, and particulate matter from
smokestacks.
(6)
Part 4. Air pressure, mass and motion. Is air heavy?
10. Different gases have different densities. Compare and contrast the behavior of
equalsized balloons filled with available gases such as natural gas from a burner jet which is
mainly methane CH4 , “air” = 79% N2 + 20% O2 + Ar, CO2 and other trace gases), or carbon
dioxide CO2 if available, by attempting to throw the balloons evenly and carefully. Which has
the greatest and least mass? _____________________________________________________ (2)
The Ideal Gas Law is given by: PV = nRT this can be rearranged to give n/V = P/RT . This
reads: the number of moles of a gas divided by its volume (how many particles per volume)
equals its pressure divided by the gas constant times its absolute temperature. If we
multiply both sides by the molar mass of the gas (M) with units of grams per mole, we get
the moles to cancel on the right giving grams per liter or gas density. Refer to Table 1
throughout section.
This looks like: Mn/V = MP/RT or ρ = MP/RT because of this we can work with pure
samples of gas to determine gas densities, molecular weights of number of moles of particles
which is pretty handy when dealing with light invisible things that might be toxic!
Why do some gases weigh more than others at the same T°C and Patm? _______________
_______________________________________________________________________________
_______________________________________________________________________________ (2)
5
13. What consequences does this gas density variation have for the composition of air given:
N2 – 28g/mol, O2 – 32 g/mol, CO2 - 44 g/mol and O3 - 48 g/mol (ozone), N2O – 44, C6H6 – 126
benzene, CO – 28 g/mol, Rn – (222) g/mol.
a. Mountain Climbers and Pilots? Include where you can climb or fly higher without aid of
oxygen masks? _________________________________________________________________
_______________________________________________________________________________ (2)
b. Trees, shrubs and higher vascular plants? Include the variation in the elevation of tree line
equator to pole and why on Hawaii some plants like Coconut Palms only grow near Sea
level while Coffee bushes can also grow at higher elevations? _________________________
_______________________________________________________________________________
_______________________________________________________________________________ (2)
c. Where would you most likely find a breath of “fesh air” in a burning building and why?
________________________________________________________________________________
________________________________________________________________________________
_______________________________________________________________________________ (2)
d. Assume that smog from incomplete combustion and exhaust build up contains more than
its fair share of: CO2 , O3 , N2O, C6H6 and other gaseous by products. Explain why this builds
up at street level in cities during the day but falls at night through early morning? _______
_______________________________________________________________________________
________________________________________________________________________________
_______________________________________________________________________________ (2)
e. Unlike (d) above, explain why mines and basement suites might not have very healthy air
quality from the above list? ______________________________________________________
________________________________________________________________________________
_______________________________________________________________________________ (2)
Table 1: Gas Properties
Gas
Air
Ammonia
Argon
Benzene
Carbon dioxide
Carbon disulphide
Carbon Monoxide
Chlorine
Helium
Hexane
Hydrogen
Hydrogen chloride
Formula
~N2 + O2
NH3
Ar
C6H6
CO2
CS2
CO
Cl2
He
C6H14
H2
HCl
Mol.wt.
28.89
17.03
39.95
78.11
44.01
76.13
28.01
70.91
4.02
86.17
2.02
36.50
6
Density (g/L
)
1.293
0.769
1.783
3.486
1.977
Vol.Pet.Liq.
1.250
2.994
0.179
Vol.Pet.Liq.
0.090
1.528
use
Troposphere & higher
Industrial base, fertilizer
Decay product of 40K, inert stable
Gasoline molecule, aromatic
Combustion product, acidic
Organic solvent
Incomplete combustion
Water treatment, WWI Ypres
U, Th decay from rocks, soils
Gasoline molecule
Electrolysis, reduction of acid
Hydrochloric acid in H2O
Hydrogen sulfide
Methane
Natural Gas
Nitrogen
H2S
CH4
~CH4 +
N2
34.08
16.04
19.50
28.02
Nitrous oxide
Nitrogen dioxide
Nitrogen trioxide
N2O
NO2/N2O4
N2O3
44.01
46.01
76.01
Oxygen
Ozone
Phosgene
Propane
Freon 12, Dichlorofluoro
methane
Freon 22, Chloro
difluoromethane
Radon
Sulphur dioxide
Water vapour, steam
O2
O3
COCl2
C3H8
32.00
1.429
48.00
2.140
98.91 Vol.Liquid
44.09
1.882
CCl2F2
120.93
CHClF2
Rn
SO2
H2O
86.47
222.00
64.06
18.02
1.434
0.717
0.800
1.251
Sour gas, hot springs, sulfides
pure compound
in nature
in air
lightning, combustion, acidic, propellant,
1.977 medicinal
2.620 lightning, combustion, acidic
lightning, combustion, oxidizing
Troposphere & higher
Stratospheric, smog
Gas Warfare
bottled gas
0.055 refrigerant, blowing gas for foams
3.660
97.300
2.926
0.804
refrigerant, blowing gas for foams
radioactive noble gas from U decay
coal, diesel combustion product
drives weather, volcanoes, combustion
Part 5. To demonstrate Bernoulli’s Principle and explain its relation to air pressure
differences and what happens because of these differences (winds, storms, weather…)
Bernoulli's Principle says that the pressure decreases inside a stream of faster flowing air
relative to slower-moving surrounding air. This explains lift, entrainment and how some
pumps work.
14. Materials: Paper - Standard letter-size paper will work fine, though heavier paper stock
like resume paper or construction paper will work better.
1. Fold the piece of paper in half. 2. Then place it on the very edge of a table, so that the
paper “tunnel” points off the edge of the bench. 3. Blow a steady stream of air through the
tunnel. Try to aim so you’re blowing down by the table surface, in the center of the paper.
What happens? Draw this experiment and label the forces (pressures differ, explain why)
(3)
7
15. Rinse out two aluminum juice/pop cans of the same size: 1. Place the two empty cans
lying down a few inches apart on a flat surface. 2. Blow air downwards between the two
cans from directly above them and observe and draw or describe what happens. Try it with
the two cans very close together. Draw and label what happens. Explain or label the
pressures and note where they are different and explain why.
(3)
16. Cans: Set the cans up again as in step one and blow between the cans horizontally from
the level of the flat surface. Observe, draw and label what happens. Explain the observation. (3)
15. Bouncing Balloon in an airstream (lift in updrafts).
Equipment: balloons, string, meter stick
a. Blow up a balloon with air and tie off the end. Hold the balloon out at arm’s length and let
go of it. Does it stay there, or drop? Why?
(2)
b. Hold the balloon above your head at arm’s length, then blow hard up at it as you let go.
Can you keep the balloon in the air? Why?
(2)
c. Hold the air dryer in one hand (use the cold air setting) and point it up toward the ceiling.
Observe what happens when you let go of the balloon in the stream of moving air. Does the
balloon fall to the ground or stay up? Why does this happen?
(2)
d. Experiment further with the hair dryer. If you tilt the nozzle slowly a little to one side,
does the balloon stay in the air stream? Can you bring the nozzle back to vertical and make the
balloon follow? How far can you tilt the nozzle before the balloon falls? What causes the balloon to
stay in the stream of moving air?)
(3)
e. Try placing a small ball in the air stream created by the hot air gun. If your hot air gun is
powerful enough, the ball will float in the stream just like the balloon? Birds have much
more hollow bones than you do, to reduce the mass that the lift of air has to carry in flight.
Can you place both the balloon and the table tennis ball in the air stream at the same time? Which of
the 2 objects must be placed on top for them to both remain floating? Why is this the case?
(3)
8
f. Would you expect to be able to keep the ball up using a rubber hose with air flow from
taps on the bench? Try it and describe your results.
(2)
Part 6. Air compressibility
18. Match-head hydrometer in the Bottle
1. Obtain a tall empty bottle - such as a wine bottle, a tight fitting cork or rubber stopper, a paper match
and some water.
2. Fill the bottle up with water up to the neck near the top.
3. Cut the paper match about in half then drop the match into the water. It ought to float
vertically in a moment with the head pointing downwards. You may need long tweezers to
get it to sit correctly. It might help to wet the match first. Try this in a beaker before using
the bottle.
4. Force the cork part way into the bottle. What happens? Move the cork in and out. See if you
can even get the match to stop halfway down and rest in one place. Eventually the match
will water-log and the sulfur top will start to disintegrate so don't push your luck on this
one. Water does not compress much but the paper match has many very small air pockets.
Why do you think the match sinks? Hydrometers are manufactured devices that float like this
and are calibrated to measure the density of the liquids that they sit in. Draw & describe this
below. What kind of animals do you think take advantage of air compressibility?
(6)
9