(PASS THE PROTON, THE H1+ ION, or WHATEVER / PERIODDUE DATE
AND NEVER CALL ME ACID BREATH) / LAB WRITE-UP GRADE
Activity 1: Thinking About Acids and Bases
EXPLORATION:
1. What do vinegar, lemons, and green apples have in common?
2. What do soaps, shampoo, and detergents have in common?
3. There are towns in the United States such as Alkali Flats, Bitter Creek, Soda Springs,
etc. Why do you think the towns have names like that and what do they have in
common?
EXPLANATION:
You were correct if you said that vinegar, lemons, and green apples have a sour taste
and that they were acids. Although you should NEVER taste things that are not known
to you, you may have accidentally tasted soapy water, shampoo, or detergents and
noted that all of these cleaning agents, called bases, have a bitter taste. Alkali Flats,
Bitter Creek, and Soda Springs are so named because the soil around them is not good
for growing crops. Alkali metals in Group 1 of the Periodic Table form strong bases
when in contact with water. Soda is the shortened name for sodium and refers to
sodium compounds in the soil. Alkaline or alkali is synonymous for substances that
are basic and have a bitter taste. Soda water in contrast is acidic since it is primarily
carbonated water.
4. Write the names of all Group 1 alkali metals in the space below.
EXPLANATION:
An acid is a neutral molecule that donates positive hydrogen ions (H1+). It is the
H1+ ion in water that causes the sour taste. Strong acids and some weak acids begin
their formula with the symbol H to signify that they are acids. An ion is an atom or a
group of atoms with a charge. Below are examples of acid molecules each with its
positive H1+ and corresponding negative ion:
Table of Acids in Water Dissociated into Hydrogen Ions and Negative Ions
H2SO4 (sulfuric acid, a very strong acid; used in batteries, destroys skin) / 2 hydrogen ions2 H1+ / sulfate ion
SO42-
HCl (hydrochloric acid, strong acid in stomach; digests food, cleans bricks) / hydrogen ion
H1+ / chloride ion
Cl1-
H2CO3 (carbonic acid, a weak acid; carbonated water and soft drinks) / hydrogen ion
H1+ / bicarbonate ion
HCO31-
CH3COOH (vinegar or dilute acetic acid, a weak acid; used in cooking) / hydrogen ion
H1+ / acetate ion
CH3COO1-
H2O (water, very, very weak acid;1 out of 550,000,000 molecules forms ions) / hydrogen ion
H1+ / hydroxide ion
OH1-
Since the hydrogen ion comes from a hydrogen atom from which an electron has been
removed, the hydrogen ion is a single positive charge called a proton. Since a proton
is found only in the nucleus of an atom, a hydrogen ion is the nucleus of a hydrogen
atom; the smallest of all the atoms. The symbols H1+ and a small H in a circle with a
plus sign are synonymous for hydrogen ions or protons in drawings.
5. To show the breakup of a hydrogen atom in water, use a small circle with a H inside for the neutral hydrogen atom, the symbol for an electron, and for the proton.
EXPLANATION:
Since a proton, or H1+ ion cannot exist by itself and only in water, the proton attaches
itself to the oxygen end of a water molecule in the equation: H2O + H1+ --> H3O1+. The
H3O1+ is called a hydroniumion. Although chemists use both the hydrogen ion and the
hydronium ion interchangeably, it is always better to use the term hydronium
ion rather than hydrogen ion when talking about acids and acid properties.
6. Use two small circles with H inside for hydrogen atoms and a darkened circle for an
oxygen atom to draw a water molecule. Arrange the molecule into a /\ or V shape
with the oxygen at the point and the hydrogen atoms at the ends. Draw the formation
of a hydronium ion in the boxes below; the hydrogen ion attaches itself to the oxygen
atom of the water molecule.
7. Draw pictures of the combination of a hydrogen atom from an HCl molecule with a water
molecule to make a hydronium ion. Use small circles with the symbol H and Cl inside to
designate hydrogen and chlorine atoms in HCl and water (H2O) molecules. Use
darkened circles to represent oxygen atoms. The formulas and charges are correct as
shown. Attach positive (+) and negative (-) charges to ions as needed.
8. Draw pictures of the combination of a hydrogen atom from an acetic acid (vinegar)
molecule with a water molecule to make a hydronium ion. Use small circles with the
symbols inside for atoms in the molecules. Draw the acetic acid skeleton as CCOH.
Attach three hydrogen atoms to the first carbon atom and an oxygen atom to the middle
carbon atom. Attach positive (+) and negative (-) charges to ions as needed.
EXPLANATION:
We defined an acid molecule as a proton or hydrogen ion donor. A base is defined as a
molecule or ion that accepts a proton or hydrogen ion from an acid. Ions that are
negatively charged and molecules that have strong negatively charged areas are all
bases. Examples are:
Table of Bases in Water Dissociated into Negative Ions and Positive Ions
NaOH (sodium hydroxide, a very strong base; dissolves grease, oil, fat) / hydroxide ionOH1- / sodium ion
Na1+
Na2CO3 (sodium carbonate, a weak base; washing soda, cleaning materials) / carbonate ion
CO32- / 2 sodium ions
2 Na1+
NaCH3COO (sodium acetate, a weak base; used in hand-warmer packages) / acetate ion
CH3COO1- / sodium ion
Na1+
NH3 (ammonia, a weak base in water; household cleaner, window cleaner) / hydroxide ion
OH1- / ammonium ion
NH41+
H2O (water, very, very weak acid;1 out of 550,000,000 molecules forms ions) / hydroxide ion
OH1- / hydronium ion
H3O1+
The following equations show that all of the negative ions from the table above are
bases since they all accept protons from hydronium ions. The equations focus only
on the base ions and ignore the other ions which are present in the solution but
take no part in any of the reactions.
9. Use circles with symbols of H atoms inside and darkened circles for oxygen atoms
atoms. Attach positive (+) and negative (-) charges to ions as needed. Draw pictures
of a hydroxide ion accepting a proton from a hydronium ion to form water molecules.
10. Use circles with symbols of atoms inside and darkened circles for oxygen atoms.
Attach positive (+) and negative (-) charges to ions as needed. Draw pictures of a
carbonate ion accepting protons from hydronium ions to form carbonic acid and water.
11. Use circles with symbols of atoms inside and darkened circles for oxygen atoms.
Attach positive and negative charges to ions as needed. Draw pictures of an acetate
ion accepting a proton from a hydronium ion to form acetic acid and water.
12. Use circles with symbols of N and H atoms inside and darkened circles for oxygen
atoms. Attach positive and negative charges to ions as needed. Draw pictures of an
ammonia molecule accepting a proton from a hydronium ion to form an ammonium
ion and water. Ammonia is like a tripod where the N atom is at the top and hydrogen
atoms are the three legs. In the ammonium ion, the fourth hydrogen (a proton) sits on
top of the N atom like a camera on the tripod.
NH3 / + / hydronium ion
H3O1+ / --> / ammonium ion
NH41+ / + / water molecule
+ / --> / +
Chemical Reactions: Acids and Bases / NAME
(PASS THE PROTON, THE H1+ ION, or WHATEVER / PERIODDUE DATE
AND NEVER CALL ME ACID BREATH) / LAB WRITE-UP GRADE
Activity 2: Thinking a Little More about Acids and Bases
EXPLORATION:
1. What do you think could be done to measure the strength of an acid or a base?
2. What do you think a liquid such as water should be called if it is neither an acid nor a base?
3. How is pH used in testing swimming pool water? Ask a pool owner if you don't know.
EXPLANATION:
As shown in the drawing, the strength of an acid or a base is determined by pH which
indicates the number or amount of hydronium ions in a solution. pH means potency,
strength, or power of an acid and is based on the number of hydronium ions in a
solution. To make something less acidic or less basic, a solution is diluted with water.
To dilute an acid by one pH unit, say from pH 4 to pH 5, the amount of water
needed is 10 times the amount of solution present. To dilute a base by one pH unit,
say from pH 12 to pH 11, the amount of water needed is 10 times the amount of
solution present. In general, ten times the amount of water must be added to dilute an
acid or a base by one pH unit; a 100 times the amount of water for two pH units, a 1000
times the amount of water for three pH units, etc.
4. Describe the relationship between pH number and acid strength. Is this a direct
relationship (the bigger the pH number the stronger the acid) or is it an inverse
relationship? Explain.
5. Describe the relationship between pH number and base strength. Is this a direct
relationship (the bigger the pH number the stronger the base) or is it an inverse
relationship? Explain.
6. Use the diagram above to write a definition for an acid and a base.
7. Water is a neutral solution. Define a neutral solution in terms of numbers of hydronium
and hydroxide ions.
8. Strong acids and bases are harmful to our bodies since they destroy body cell tissues
except for the strong acid HCl in the stomach which is protected by special cells. Why
do hands turn red and dry if they are not protected when washing dishes by hand?
9. Why is it important to use lots and lots of water if you accidentally spill an acid or a base
on your skin?
(PASS THE PROTON, THE H1+ ION, or WHATEVER / PERIODDUE DATE
AND NEVER CALL ME ACID BREATH) / LAB WRITE-UP GRADE
Activity 3: Testing the pH of Liquid Household Chemicals
1. Which do you think is most acidic - lemon juice or orange juice? Why do you think so?
2. How can you tell if something is stronger or weaker? List two household chemicals
which are acids and which have different strengths.
3. List two household chemicals which are bases and which have different strengths.
Purpose: To predict and test the pH of liquid householdchemicals.
Materials needed:
a. pH paper and pH color chart
b. printer paper, 1 sheet
c. goggles
d. liquid household chemicals - vinegar, lemon juice,
orange juice, 7-Up or clear soda water, pickle
juice, Windex or diluted ammonia water, tomato
juice, liquid soap, shampoo. /
Procedure:
a. Use a pencil to draw eight large squares on a sheet of printer paper.
b. Divide a pH test strip approximately 10 cm long into eight pieces, then place one
piece into a corner in each square.
c. To test a liquid, use only the dropper from the container to drop two drops into the
center of a paper square. Write the name of the liquid below it in the square. For
saliva (the medical term is expectorate) place a small amount of expectorate into the
center of a paper square.
d. Predict in the table if the solid or liquid is an acid, base, or if it is neutra. Place one
end of the pH paper into the liquid then compare its color with the color in the pH
chart to determine pH.
Data Table: pH of Liquid Household Chemicals
testmaterial / prediction
acid/neutral/base / pH / results
acid/neutral/base / prediction is
accepted/rejected
vinegar
CH3COOH
lemon juice
C5H7COOH
orange juice
C5H7COOH
soda water
H2CO3
pickle
juice
Windex
NH4OH
tomato
juice
saliva
shampoo
liquid
soap
4. List the chemicals in the table that are acids; list them in order from the highest acidity
to the lowest acidity.
5. Lemon slices and orange slices have nearly the same acidity and pH. Why is it easier
to eat an orange than a lemon?
6. List the chemicals in the table that are bases; list them in order from the strongest base
to the weakest base.
7. Why do you suppose that most body fluids like saliva, blood, and tears have a pH that is
either neutral or close to neutral?
(PASS THE PROTON, THE H1+ ION, or WHATEVER / PERIODDUE DATE
AND NEVER CALL ME ACID BREATH) / LAB WRITE-UP GRADE
Activity 4: Testing the pH of Solid Household Chemicals
1. Why do you think water must be added to a solid to test for its pH?
2. What is meant by a neutral pH?
3. How is the pH of a solution changed if it is neutral and you add water to it?
EXPLANATION:
To test the pH of a solid, it must be dissolved in water in order to determine if ions are
released; if hydronium ions are predominantly released the solid is an acid. If negative
ions are predominantly released the solid is an base.
chemicals.
Materials needed:
a. pH paper and pH color chart
b. printer paper, 1 sheet
c. goggles
d.water in dropper bottles or Beral pipettes
e. solid household chemicals - vitamin C, dishwasher
soap, apple slice, baking soda, borax, aspirin,
washing soda, table salt, coffee, table sugar
f. tooth pick and scoop made from a drinking straw
whose end is cut diagonally /
Procedure:
a. Use a pencil to draw eight large squares on a sheet of printer paper.
b. Divide a pH test strip approximately 10 cm long into eight pieces, then place one
piece into a corner in each square.
c. To test a solid, use a scoop to place a tiny pinch of the solid in the center of a paper
square. Write the name of the solid below it in the square. Carefully add two drops
of water from a dropper or from a Beral pipette, then stir the mixture with a tooth pick.
d. Predict if the solid or liquid is an acid, base, or if it is neutral. Place one end of the
pH paper into each solution and compare its color with the chart to determine pH.
Data Table: pH of Solid Household Chemicals
testmaterial / prediction
acid/neutral/base / pH / results
acid/neutral/base / prediction is
accepted/rejected
vitamin C
pieces
dishwashing
soap
apple
slice
baking soda
NaHCO3
borax
Na2B4O7
aspirin
C6H6OCOOH
washing soda
Na2CO3
table salt
NaCl
coffee
table sugar
C12H22O11
4. List the chemicals in the table that are acids; list them in order from the highest acidity to
the lowest acidity.
5. List the chemicals in the table that are bases; list them in order from the strongest base
to the weakest base.
6. Table salt, NaCl, dissolves in water and breaks up into ions whereas table sugar does
not produce ions when dissolved in water. Why is it that both solutions have a pH of 7?
(PASS THE PROTON, THE H1+ ION, or WHATEVER / PERIODDUE DATE
AND NEVER CALL ME ACID BREATH) / LAB WRITE-UP GRADE
Activity 5: Color Changes Involving Acids and Bases
EXPLORATION:
Gardeners can change the colors of hydrangea flowers by the type of fertilizer they
apply. Acid fertilizer colors the flowers blue; a base fertilizer colors them red. You may
have watched your parents place lemon into tea. A lemon lightens the color of dark tea.
Cabbage cooked in vinegar is red. And, cabbage cooked with baking soda is blue.
1. What two things do hydrangea flowers, cabbage, and tea have in common in the
examples above? Explain
EXPLANATION:
Hydrangea flowers, cabbage, and tea are plant materials. They are all sensitive to acids
and bases and are called indicators. An indicator is a chemical that indicates by color if
a substance is an acid, a base, or neutral. Magic inks and magic pens use indicators to
achieve a color change or to make writing disappear.
Purpose: To test indicators such as cabbage, geranium flowers, grape juice or grape jelly,
and bromthymolblue for color changes in acids and bases.
Materials needed:
a. printer paper
b. raw piece of red cabbage, red flowers such as geranium, grape juice or grape jelly
c. dropper bottles or Beral pipettes: bromthymolblue indicator, vinegar, HCl (0.5M),
Windex, NaOH (0.5M)
d. cotton swabs or cotton buds
e. goggles
Procedure:
a. With the data table below as a model, use a pencil to divide a sheet of printer paper
into squares with five columns and four rows leaving small margins for writing on top
and to the left. In the margin to the left of Row 1 write cabbage, to the left of Row 2
write red geranium, to the left of Row 3 write bromthymolblue and to the left of Row
4 write grape. In the margin on top of the columns write normal above Column 1,
vinegar above Column 2, HCl above Column 3, Windex above Column 4, and NaOH
above Column 5.
b. Use your thumb to press red cabbage stains across the squares in Row 1and red
geranium flower stains across the squares in Row 2. Use a cotton swab to smear
grape juice or jelly stains across the squares in Row 3 and a dropper to smear
bromthymolblue stains across the squares in Row 4.
c. With a dropper or a Beral pipette, place a drop of vinegar on top of each stain in
Column 2, a drop of HCl on top of each stain in Column 3, a drop of Windex on top of
each stain in Column 4 and a drop of NaOH on top of each stain in Column 5.
d. Record all colors in the data table below.
Data Table: Colors of Indicators in Acid and Bases
indicator / normal color / color with vinegar / color with HCl / color with Windex / color with NaOHred cabbage leaf
red flower from a geranium plant
bromthymolblue indicator
grape juice or dark colored jelly
2. Is there a difference in indicator color between vinegar and HCl? Explain.
3. Is there a difference in indicator color between Windex and NaOH? Explain.
4. Suppose that a normal cabbage stain changed color due to a drop of Windex in contact
with the stain. Why will adding a small amount of vinegar on top of the Windex drop
change the color back to the normal cabbage color? Explain.
5. Suppose that a normal cabbage stain changed color due to a drop of NaOH added to
the stain. Predict what happens if a drop of HCl are added?