quiz of the day – no notes please take out a separate sheet of paper. put name in upper right...

Quiz of the Day – No notesQuiz of the Day – No notesPlease take out a separate sheet of paper. Put Please take out a separate sheet of paper. Put

name in upper right corner:name in upper right corner:

1)1) Which salt makes up the largest percentage of salt Which salt makes up the largest percentage of salt dissolved in seawaterdissolved in seawater

a.a. Sodium chloride (NaCl)Sodium chloride (NaCl)b.b. Magnesium chloride (MgCl2)Magnesium chloride (MgCl2)c.c. Calcium carbonate (CaCO3)Calcium carbonate (CaCO3)d.d. None of the aboveNone of the above

2)2) Define salinityDefine salinity3)3) Why is the ocean salty? Why are lakes and rivers not salty?Why is the ocean salty? Why are lakes and rivers not salty?4)4) What is the average salinity of the oceans?What is the average salinity of the oceans?

a. 15 ppt (1.5%)a. 15 ppt (1.5%)b. 35 ppt (3.5%)b. 35 ppt (3.5%)C. 350 ppt (35%)C. 350 ppt (35%)d. 2.72 ppt (0.272%)d. 2.72 ppt (0.272%)

HydrometerHydrometerHydrometer: An instrument used to Hydrometer: An instrument used to measure the “relative density” of liquids.measure the “relative density” of liquids.

““Relative density”: The ratio of the density Relative density”: The ratio of the density of a substance to the density of pure water. of a substance to the density of pure water. Pure water is assigned a density of 1.Pure water is assigned a density of 1.

Examples: Examples:

Wood <1Wood <1

Metal >1Metal >1

Make a better HydrometerMake a better HydrometerOn the front table is a variety of On the front table is a variety of

supplies to make a better supplies to make a better hydrometer. Your mission will be hydrometer. Your mission will be to create a better hydrometer to to create a better hydrometer to

compare the density of water with compare the density of water with varying amounts of saltvarying amounts of salt

Making the hydrometer-materialsMaking the hydrometer-materials

You will need a piece of graph paper to You will need a piece of graph paper to record your lab design and to record and record your lab design and to record and graph your data for the comparison of graph your data for the comparison of density and salinity lab.density and salinity lab.

The following may be used to design your The following may be used to design your hydrometer:hydrometer:

Straws, coffee stirrer, clay (there are Straws, coffee stirrer, clay (there are different types) tape (to create different types) tape (to create measurements), ball bearings/bb’s, rubber measurements), ball bearings/bb’s, rubber stoppersstoppers

Making the hydrometerMaking the hydrometer

Look at the designs of the example hydrometers, Look at the designs of the example hydrometers, think about what might help them work well think about what might help them work well and what flaws they may have. Make sure that and what flaws they may have. Make sure that your design includes the following: your design includes the following:

1.1. You must have a measuring scale on your You must have a measuring scale on your hydrometer in mm. Use the tape and mark off hydrometer in mm. Use the tape and mark off each mm. Make your 5mm marks longer (so each mm. Make your 5mm marks longer (so 5mm, 10, 15, 20, etc will be more visible)5mm, 10, 15, 20, etc will be more visible)

2.2. The 0 mm. will be at the The 0 mm. will be at the top top of your of your hydrometer (opposite end of the “bulb”)hydrometer (opposite end of the “bulb”)

3.3. Make sure your hydrometer floats upright. The Make sure your hydrometer floats upright. The higher your hydrometer floats the greater the higher your hydrometer floats the greater the density of the liquid in which the hydrometer is density of the liquid in which the hydrometer is floatingfloating

Making the hydrometerMaking the hydrometer

Testing your hydrometerTesting your hydrometer Use 90 ml of water. Place your Use 90 ml of water. Place your

hydrometer in the water and make sure hydrometer in the water and make sure it floats but that it is low in your water. it floats but that it is low in your water. Add weight if necessary. Make sure the Add weight if necessary. Make sure the hydrometer remains upright, so that you hydrometer remains upright, so that you can easily measure. Make sure you can easily measure. Make sure you have done the marks in waterproof ink.have done the marks in waterproof ink.

Using your hydrometer:Using your hydrometer:Comparing density and SalinityComparing density and Salinity

1.1. Fill a 100ml Graduated cylinder with Fill a 100ml Graduated cylinder with 90 ml of water. Place your 90 ml of water. Place your hydrometer in the water.hydrometer in the water.

2.2. Create a data table. In your data Create a data table. In your data table, record what the water comes table, record what the water comes to on your mm scale (measure from to on your mm scale (measure from top down)top down)


Data TableData Table

Total Total Salt Salt (grams)(grams)

00 11 3.53.5 1212 4545 Sample Sample AA

Sample Sample BB

ExampleExample Fresh Fresh waterwater

BrackisBrackish Waterh Water

Salt Salt waterwater

Great Great Salt Salt LakeLake

DeaDead d SeaSea

HydroHydrometermeterReadinReading(mm)g(mm)


3.3. Remove the hydrometer and mix in Remove the hydrometer and mix in 1 g of salt. Replace the hydrometer 1 g of salt. Replace the hydrometer and record the water leveland record the water level

4.4. Repeat step 3 four more times, Repeat step 3 four more times, each time increasing the TOTAL each time increasing the TOTAL amount of salt to the water. Record amount of salt to the water. Record the water level each time in the the water level each time in the data tabledata table

5.5. Plot your data on a graph, making Plot your data on a graph, making sure to label your x and y axis.sure to label your x and y axis.


Conclusion:Conclusion:Make sure to include the following in your Make sure to include the following in your

conclusion:conclusion: Why did you design the hydrometer the Why did you design the hydrometer the

way you did? Did it float? Were you able way you did? Did it float? Were you able to use it to measure density?to use it to measure density?

What did your data show you about What did your data show you about salinity and density?salinity and density?

What general conclusion can you make What general conclusion can you make about increasing salinity in water? about increasing salinity in water?

Clean UpClean Up

1.1. Make sure to rinse your graduated Make sure to rinse your graduated Cylinder and return it to the prep Cylinder and return it to the prep table.table.

2.2. Clean up any spilled salt and wipe Clean up any spilled salt and wipe down lab space.down lab space.

3.3. Turn in lab papers to Period 4 slotTurn in lab papers to Period 4 slot

To be turned in at 9:45amTo be turned in at 9:45amLab write up with:Lab write up with:

Two namesTwo names

Sketch of hydrometerSketch of hydrometer

Table and GraphTable and Graph

Conclusions:Conclusions: Why did you design the hydrometer the way Why did you design the hydrometer the way

you did? Did it float? Were you able to use you did? Did it float? Were you able to use it to measure density?it to measure density?

What did your data show you about salinity What did your data show you about salinity and density?and density?

What general conclusion can you make What general conclusion can you make about increasing salinity in water?about increasing salinity in water?

quiz of the day – no notes please take out a separate sheet of paper. put name in upper right...

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