Transcript snc1l u3l15 acids and bases lab

Lesson 15
Acids
 Acids are traditionally considered any chemical
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compound that, when dissolved in water, gives a pH
of less than 7.0. They also:
Taste sour
Are good conductors of electricity (they release H+
ions when they are in water)
React with compounds that contain carbonate
Are generally quite reactive
Turns litmus red
React with bases
Acids
 Acids are widely used in industry, they are used in
many manufacturing processes including; fertilizers,
explosives, refining oil, and electroplating materials.
Table 1 : Examples of common
acids
Common name
Formula
Source or use
Vinegar (acetic acid)
HC2H3O2
Salad dressing
Citric acid
HC6H7O7
Oranges, lemons
Ascorbic acid
HC6H7O6
Vitamin C
Lactic acid
HC3H5O3
Sulfuric acid
H2SO4
Sour milk or tired
muscles
Car batteries
Base
 A base is most commonly thought of as an aqueous
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substance with a pH higher than 7.0 at standard
conditions. They also:
Taste bitter
Are good conductors of electricity (They release
OH- ions when dissolved in water)
Break down proteins into smaller molecules
May also be called alkaline
Turns litmus blue
React with acids
Table 2 Examples of some common
bases
Common Name
Formula
Source or use
Sodium hydroxide
NaOH
Drain cleaner
Potassium hydroxide
KOH
Soap, cosmetics
Aluminum hydroxide
Al(OH)3
Antacids
Ammonium
hydroxide
NH4OH
Window cleaner.
pH
 The pH scale is used to represent how acid or basic a
solution is. The scale ranges from 0-14 with very acidic
being 0, neutral being 7, and very basic being 14.
pH
Chemical Changes with Acids and
Bases
 Yeast is called a raising agent. The carbon dioxide it
produces “raises” the bread and makes it lighter.
Baking powder is another type raising agent. Baking
powder is often used in making cakes and cookies
because it works fast than yeast.
 Baking soda is a base.
 Vinegar is an acid.
 Mixing them together produces a bubbling action.
Baking powder releases carbon dioxide in the same
way.
Ingredients:
 Cream of tartar (acid)
 Baking soda (base)
 Corn starch (filler)
 The filler keeps the acid and base separated. The filler
also absorbs any moisture that might get into the
baking powder. When you add a liquid such as water to
baking powder, the dry acid and dry base dissolve. The
acid and base react to produce carbon dioxide bubbles.
Questions:
 What is baking powder used for?
 Why is corn starch added to baking powder?
 Why isn’t vinegar used as the acid in baking powder?
Raising Agent Lab
Question
 Which raising agent produces carbon dioxide the
fastest?
Safety precautions
 Clean up the work area and wash your hands
thoroughly at the end of the activity.
 Never eat anything that has been made in a science
room
Experimental Design
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Use the tape and pencil to label the three beakers:
baking soda, vinegar, and baking powder.
Add raising agent to its cylinder
Add 25 mL of egg white solution to each cylinder
Swirl each cylinder gently to mix
Measure the height of the foam in each cylinder
every three minutes for 9 minutes
Record the results in the table.