Properties of Water
A.
B.
C.
D.
E.
Density and Salinity
Buoyancy
Sensible heat of sea water and air
Mass and Weight of water
E. The effects of Salts on
A. Density and Salinity
Purpose: Compare the densities of fresh and salt water.
Assess how salts affect the density of water.
1) Hydrometer Method
• Use the hydrometer and a graduate or plastic tube to measure the density of the water and the
temperature of the water. Record the results below.
Table 1:
Fresh Water
Sea water
Density
Temperature
Salinity
2) Refractometer Method
• Place a drop of water and read the salinity and density. Measure the temperature of the water.
Table 2:
Fresh Water
Sea water
Density
Salinity
Temperature
3) Evaporation Method
• Label one 250 ml beaker fresh water and another 250 ml beaker.
• Measure the mass of two 250 ml beakers
• Add 100 ml of fresh water to one beaker and 100 ml of sea water to the other beaker.
• Mass both beakers and water sample.
• Calculate the density of each water sample.
• Place both beakers in the oven to evaporate the liquid.
• Remove beaker from the oven and mass the beaker and residue.
• Calculate the mass of the residue.
• Calculate the salinity.
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Table 3:
Fresh Water
Sea Water
Mass of Beaker
Mass of Beaker and Water
Mass of Water sample
Volume of Water Sample
Density of Water Sample
Mass of residue
Salinity of Water Sample
Using Graph figure 2.1 respond to the following.
1.
2.
3.
What is the density of a water sample with a salinity of 37 ppt at 28˚ C? _______________
What is the density of a water sample with a salinity of 32 ppt at 13.5˚ C? _______________
In terms of salinity and temperature how do you explain this relationship with density?
B. Buoyancy
Purpose: Compare the buoyancy forces of air, fresh water, salt water and cold salt water on an
object.
•
•
•
•
Take a 250 ml beaker, a rubber stopper, and a spring balance.
Hang the stopper from the balance a determine the weight if the stopper in air. Record the
weight in air.
Suspend the stopper on the spring balance in the fresh water sample in the beaker, being sure that
the stopper does not touch the bottom or sides of the beaker and that the stopper in completely
under water. Record the weight of the stopper in fresh water.
Repeat the procedure for a room temperature salt water sample and a cold salt water sample.
Table 4:
Object -_________________________________________
Spring Scale
Stopper
Mass (g)
Mass in Air (Stopper)
air temp =
Mass in fresh water
water temp =
Mass in sea water
water temp =
Mass in cold sea water
water temp =
2
Electronic Scale
System
Mass (g)
C. Latent Heat of Water
Purpose: Compare the slatent heat characteristics of water and air.
Definition: The heat released or absorbed per unit mass by a system in a reversible isobaricisothermal change of phase. In meteorology, the latent heats of evaporation (or condensation), fusion
(melting), and sublimation of water substance are of importance.
•
•
•
•
Take two black calorimeters sets, two thermometers, and a light source.
Fill one with sea water and the other with air.
Place both an equal distance from the light source and record the temperature of each every 5 minutes
for about 45 minutes.
Turn off the light and record the temperature every five minutes.
Volume of container = _____________
Table 5:
Time
0
5
10 15 20 25 30 Change
in temp
35
40
45
50
55
60
Change
in temp
Sea water
Air
D. Mass and weight of water
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Measure 100 ml of water and place it in a pre-massed graduate.
Mass the water sample.
What would be the mass of a liter of water?
What would be the mass of a gallon of water?
What would be the mass of a cubic foot of water?
What would be the mass of a cubic meter of water?
Conversion links:
http://www.sciencemadesimple.net/EASYvolume.html
http://convert.french-property.co.uk/#volume
http://www.wsdot.wa.gov/Metrics/factors.htm#volume
Table 6:
Fresh Water
Mass of Beaker and Water
Mass of Beaker
Mass of Water sample
Volume of Water Sample
Density of Water Sample
Mass of a cubic meter of water
3
Sea Water
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E. The effects of Salts on the Freezing Points and Boiling Points of Fresh and Salt water
Purpose: Does the addition of salts affect the boiling and freezing points of water?
1) Effects of salts on the freezing point of water
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Place 150g of crushed ice in beaker 1
Place 150g of crushed ice in beaker 2
Measure the temperature of the ice in each beaker
Pour 5 g of salt into the ice in beaker 1
Observe and record the temperature in each beaker.
2) Effects of salts on the boiling points of fresh and salt water
 Place 150g of fresh water in a beaker
 Place 150g of salt water in a second beaker
 Place both beakers on a hot plate.
 Record temperatures of each water sample
 Turn on heat source/hot plate
 Record the temperature every 2 minutes until the boiling points are indicated.
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