Transcript document

Prep.
► Photocopy pH
activity from “Marine Life,” by
Dudley.
► Prep. cups with seawater and filtered water.
► Stirring rods or skewers
Do Now (8 min.)
► Read
background information.
► Read the “Question”
► Come up with a hypothesis.
What solution can buffer
pH better – filtered or sea
water? –
An Experimental Approach
Mr. M. Gonzalez
Objectives
►I
can properly use lab equipment.
► I can change the pH of a solution using an acid.
► I can explain the difference in buffering capacity
between filtered and sea water.
Buffering Capacity
► The
Buffering Capacity of a solution is the
ability that solution has to resist changes in it’s
pH.
► In other words, if you add a base or acid to the
solution the pH will change more slowly if the
solution has a high buffering capacity.
Buffering Capacity
► The
Buffering Capacity is determined by certain
salts or molecules in the water such as Calcium
Carbonate, Bicarbonate and others.
Review Writing a Hypothesis
► How
is a hypothesis written?
 A hypothesis is written as an if…then…because
statement.
► Can
you give an example of a hypothesis?
 If an acid is added to filtered and seawater then the
pH will fall faster in the filtered water because is
pure and will not be able to buffer.
Activity
► Read
Procedures and wait for instructions to
begin lab.
► REMEMBER, You will only be adding 2 drops
of acid at a time to each solution.
► TO SAVE TIME, one group will work with the
filtered water and another with the seawater.
What’s today’s lab about?
► Write
your answers on the next page of the
worksheets.
► WASH
YOUR HANDS BEFORE LEAVING.
► BE SAFE.
► BRING THE WORKSHEET BACK
TOMORROW FOR CLASS.
Clean up.
► Measuring
pH
 Rinse the probe after each
sample solution.
 Read other assigned
samples.
 After your final rinse
place 2 drops of pH
storage solution into the
little cup located inside
the probe cap.
Clean up
► Clean-up
 Recap the probe FIRMLY by lining up the lettering on the cap and the
face of the meter.
 Wait for clean-up instructions.
 Clean up your area, dump your rinse water out, dispose of gloves, and
return materials.
 Begin work on your bar graph and analysis questions.
Log activity
► Explain
how to properly use a dropper bottle?
► Explain the difference in buffering capacity
between filtered and sea water.