Make a better Hydrometer

1
Make a better Hydrometer

• On the front table is a variety of supplies to
  make a better hydrometer. Your mission will be
  to create a better hydrometer to measure salinity
  in salt water and to use your hydrometer to
  compare density and salinity

2
Making the hydrometer-materials

• You will need a piece of graph paper to record
  your lab design and to record and graph your data
  for the comparison of density and salinity lab.
• The following may be used to design your
  hydrometer
• Straws, coffee stirrer, clay (there are different
  types) tape (to create measurements), sharpie,
  ball bearings, rubber stopper

3
Making the hydrometer

• Look at the designs of the example hydrometers on
  the
• table, think about what might help them work
  well and what flaws they may have. Make sure
  that your design includes the following
• You must have a measuring scale on your
  hydrometer in mm. Use the tape and mark off each
  mm. Make your 5mm. marks longer (so 5mm, 10, 15,
  20, etc will be more visible)
• The 0 mm. will be at the top of your hydrometer
  (opposite end of the bulb)
• Make sure your hydrometer floats upright. The
  higher your hydrometer floats the greater the
  density of the liquid

4
Making the hydrometer

• Testing your hydrometer
• Use 500 ml of water. Place your hydrometer in
  the water and make sure it floats but that it is
  low in your water. Make sure it remains upright,
  so that you can easily measure. Make sure you
  have done the marks in waterproof ink.

5
Using your hydrometerComparing density and
Salinity

1. Fill a 500 ml beaker with 300 ml of water. Place
   your hydrometer in the water.
2. Create a data table. In your data table, record
   what the water comes to on your mm scale

6
Using your hydrometerComparing density and
Salinity

• Data Table

Amount of Salt 0 grams 3 grams 6 grams 9 grams
Hydrometer Reading
7
Using your hydrometerComparing density and
Salinity

• Remove the hydrometer and mix in 3 g of salt.
  Replace the hydormeter and record the water level
• Repeat step 3 four more times, each time adding 3
  more grams of salt to the water. Record the
  water level each time in the data table
• Plot your data on a graph, making sure to label
  your x and y axis.

8
Using your hydrometerComparing density and
Salinity

• Conclusion
• Make sure to include the following in your
  conclusion
• Why did you design the hydrometer the way you
  did? Did it float? Were you able to use it to
  measure density?
• What did your data show you about salinity and
  density?
• What general conclusion can you make about
  increasing salinity in water?