Do Now:
1. Don’t loose your identification
card.
2. In your notebook, define “acid”,
“base”, and “buffer”
Agenda:
Return- Microscope Quiz
Return- Microscope Lab
Demo- Buffer
Lab- Effectiveness of Antacids
Homework:
Enjoy your afternoon!
Return Microscope Quiz
Return Microscope Lab
ACID- Any substance which releases
H+ (hydrogen) ions in water.
pH range- below 7
Marshmallow
BASE:
Any substance which releases OH(hydroxide) ions in water.
pH range- above 7
Paperclip, Marshmallow, Lifesaver
BUFFER:
a strong acid/base that reacts with
a weak acid/base to neutralize the
pH of a solution.
2 Paperclips twisted (taped) together
Buffer Demo
ACIDMarshmallow
BASE-
Paperclip, Marshmallow, Lifesaver
BUFFER-
2 Paperclips twisted (taped) together
DEMO: Room= Beaker of water
Bases enter the beaker.
What happens to the pH?
Acids enter the beaker.
What happens to the pH?
What did the bases turn into?
Buffers enter the beaker.
What happens to the pH?
Add a few acids.
What happens to the pH?
Eventually what happens to the pH?
Why?
With your partner,
complete the Prelab Questions
Effectiveness of Antacids
Preparing Antacid Solution
1.
2.
3.
4.
5.
6.
7.
Crush antacid tablet using mortar and pestle.
Measure 1g of antacid using the scale.
Place the 1g of antacid into your cup.
Add 100mL of water to cup
Mix using the glass stirring rod, until antacid is
completely dissolved.
Using the pH strips, determine the initial pH
Record the Initial PH for antacid 1 in Table 1.
Adding Acid to Antacid
1.
2.
3.
4.
Add 10 drops (0.5mL) of vinegar (acid) to your cup &
stir using the stirring rod.
Observe and determine pH. Record the pH in Table
#1 for Antacid 1 under “0.5mL”
Continue adding 10 drops to your solution, stirring
each time. Measure the pH after each set of drops
and record in Table 1 until the solution reaches a pH
of 4.
When/if you reach 5mL of acid and the pH hasn’t
dropped to 4 yet, increases doses to 20 drops each
trial.
Sharing Data
5.
6.
7.
8.
Share your data with another team and copy their
data onto your Table #1. Table #1 should now have
two teams work.
Graph both teams data to have a comparison of
antacid effectiveness.
X axis- independent variable (scientists change)
Y axis- dependent variable (scientists measure)
Inform the teacher how many mL of acid was added
to reach the pH of 4. This will be used for the class
data.
Copy class’ data into Table #2.
Clean Up
Dump liquid down sink.
Wash with soap and dry the plastic cup.
Wash with soap and dry mortar & pestle.
Wash with soap and dry glass stirring rod.
Put the lid back on the jar of vinegar.
Throw out used pH strips & weighing paper.
Your table should be as neat as you found it.