Toxins Unit – Investigation IV Lesson 1: Heartburn
Toxins Unit – Investigation IV
Lesson 1:Heartburn
Unit IV • Investigation IV-X
ChemCatalyst • Countless products are advertised on TV
with the promise of reducing acid indigestion. – What is acid indigestion? What is
acidity?– What does acid have to do with your
stomach?– How do you think acid “reducers”
work?
Unit IV • Investigation IV-X
The Big Question
– What are some characteristics of solutions that are acidic, basic, or neutral?
Unit IV • Investigation IV-X
You will be able to:
• Describe the differences among acidic, basic, and neutral solutions.
Unit IV • Investigation IV-X
– Indicators: A set of substances that respond to other substances with vivid color changes.
Notes
Unit IV • Investigation IV-X
Activity
• Purpose: This activity will introduce you to a special category of solution.
(cont.)
Unit IV • Investigation IV-X
• Safety note: Do not get acids and bases on your skin. In case of a spill, rinse with large amounts of water. Wear goggles.
(cont.)
(cont.)
Unit IV • Investigation IV-X
Substance Formula Cabbage Juice
Indicator color
Indicator number
table salt (aq) NaCl
vinegar (aq) C2H4O2
rubbing alcohol C3H8O
ammonium hydroxide (aq)
NH4OH
distilled water H2O
stomach acid (aq) HCl
washing soda (aq)
Na2CO3
lemon juice C6H8O7
drain cleaner (aq) NaOH
Unit IV • Investigation IV-X
1470
(cont.)
(cont.)
Unit IV • Investigation IV-X
Observations when added to CaCO3
water
stomach acid
vinegar
drain cleaner
(cont.)
Unit IV • Investigation IV-X
Making Sense
– Look for patterns in the names, chemical formulas, uses, and properties of the substances you tested.
– List four characteristics of acids. – List four characteristics of bases.
Unit IV • Investigation IV-X
• Indicators can be used to identify substances that are acidic, basic, and neutral when dissolved in water. – Acids turn cabbage juice pink and are between 0 and
7 on the universal indicator scale. – Bases turn cabbage juice green or blue and are
between 7 and 14 on the universal indicator scale. – Neutral substances do not change color with
cabbage juice and are at or very near 7 on the universal indicator scale.
(cont.)
Notes
Unit IV • Investigation IV-X
– pH scale: A number line from 0 to 14. The numbers are associated with indicator colors.
– The numbers associated with indicator colors are also called pH numbers or simply pH.
(cont.)
Unit IV • Investigation IV-X
Check-In
– An unknown substance is purple with cabbage juice and does not react with calcium carbonate. Is it an acid, base or neutral substance? Explain.
Unit IV • Investigation IV-X
Wrap-Up
– Acids and bases are different types of solutions and are classified according to their observable behavior.
– Acids and bases respond differently to indicators. Depending on the indicator, different colors will form that show either an acidic or basic substance.
Toxins Unit – Investigation IV
Lesson 2:Watered Down
Unit IV • Investigation IV-X
ChemCatalyst
– Describe what you observe in the three vials.
– What is one explanation for the differences you observe?
– If you tested each solution with universal indicator before putting in the gummy bears, what colors would you expect to see?
Unit IV • Investigation IV-X
The Big Question
– How does dilution affect the acidity or basicity of a solution?
Unit IV • Investigation IV-X
You will be able to:
• Explain how dilution affects the concentration and pH of a solution.
Unit IV • Investigation IV-X
Activity
• Purpose: In this activity you will examine the effect of concentration on acidity and basicity of solutions.
(cont.)
Unit IV • Investigation IV-X
• Safety note – Do not get acids and bases on your skin. In case of a spill, rinse with large amounts of water. Wear goggles.
(cont.)
(cont.)
Unit IV • Investigation IV-X
Well # Concentration Color pH number
1.0 M HCl
0.10 M HCl
0.010 M HCl
0.0010 M HCl
0.00010 M HCl
0.000010 M HCl
0.0000010 M HCl
0.00000010 M HCl
0.000000010 M HCl
Data Table for dilution of 1.0 M HCl
Unit IV • Investigation IV-X
Data Table for dilution of 1.0 M NaOH
Well # Concentration Color pH number
1.0 M NaOH
0.10 M NaOH
0.010 M NaOH
0.0010 M NaOH
0.00010 M NaOH
0.000010 M NaOH
0.0000010 M NaOH
0.00000010 M NaOH
0.000000010 M NaOH
Unit IV • Investigation IV-X
Data Table for dilution of 1.0 M NaCl
Well # Concentration Color pH number
1.0 M NaCl
0.10 M NaCl
0.010 M NaCl
0.0010 M NaCl
0.00010 M NaCl
0.000010 M NaCl
0.0000010 M NaCl
0.00000010 M NaCl
0.000000010 M NaCl
Unit IV • Investigation IV-X
Making Sense
– What does concentration have to do with the acidity or basicity of a solution?
Unit IV • Investigation IV-X
1470
More H+ More OH–
pH scale
Notes
(cont.)
Unit IV • Investigation IV-X
• Arrhenius definition:– An acid is any substance that adds a
hydrogen ion (H+) to the solution.– A base is any substance that adds a
hydroxide ion (OH–) to the solution.
(cont.)
(cont.)
Unit IV • Investigation IV-X
• HA H+ + A–
• XOH X+ + OH–
(cont.)
Unit IV • Investigation IV-X
Check-In
– Lemon juice has a pH of about 2. What does this tell you about what is in the solution?
– What would happen if you diluted this solution?
Unit IV • Investigation IV-X
Wrap-Up
– The acidity and basicity of a solution are related to the concentration of the solution. Dilute solutions are less acidic and basic than more concentrated solutions.
– Dilution of an acid or a base results in a solution that is increasingly neutral.
(cont.)
Unit IV • Investigation IV-X
– The pH scale is related to the concentration of H+ and OH– ions in solution.
– According to Arrhenius, an acid is any substance that adds a hydrogen ion (H+) to the solution and a base is any substance that adds a hydroxide ion (OH–) to the solution.
Toxins Unit – Investigation IV
Lesson 3:pHooey!
Unit IV • Investigation IV-X
ChemCatalyst • Examine the following data:
Substance pH
0.10 M HCl 1.0
0.010 M HCl 2.0
0.0010 M HCl 3.0
1.0 M NaOH 14.0
0.10 M NaOH 13.0
0.010 M NaOH 12.0
Water 7.0(cont.)
Unit IV • Investigation IV-X
– What do you think pH really represents?
– How does the concentration of the solutions relate mathematically to the pH of the solutions?
(cont.)
Unit IV • Investigation IV-X
The Big Question
– How does pH relate to the concentrations of acidic and basic solutions?
Unit IV • Investigation IV-X
You will be able to:
• Find the pH of a solution if you know the concentrations of hydrogen or hydroxide ions that it contains.
Unit IV • Investigation IV-X
Activity
• Purpose: You will explore the relationship between pH, pOH, [H+], and [OH–].
(cont.)
Unit IV • Investigation IV-X
Substance Acidic or
Basic?
pH [H+] (in decimal)
[H+] (in scientific
notation)
1 M HCl
Stomach acid (0.1 M HCl) Acidic 0.1 M 1.0 10–1 M
Clear Soda 3 0.001 M
Rain Water Acidic 1.0 10–6 M
Distilled Water 7 0.0000001M
Alcohol Neutral
Salt Water 0.0000001 M
Washing Soda Basic 8 1.0 10–8 M
Ammonia 0.0000000001 M 1.0 10–10 M
Drain Cleaner (0.1 M NaOH)
13
1 M NaOH 1.0 10-14 M
Unit IV • Investigation IV-X
Well pH [H+] [OH–] pOH
A 1 1.0 10–1 M 13
B 2 1.0 10–2 M 1.0 10–12 M
12
C 3 1.0 10–3 M
D 4 1.0 10-4 M 1.0 10–10 M
10
E 5 1.0 10–5 M
F 6 1.0 10–6 M
G 7 1.0 10–7 M
H 7 1.0 10–7 M 1.0 10–7 M 7
I 7 1.0 10–7 M 7
HCl
Unit IV • Investigation IV-X
Well pH [H+] [OH–] pOH
R 7 1.0 10–7 M 1.0 10–7 M 7
Q 7 1.0 10–7 M 7
P 7 1.0 10–7 M
O 8 1.0 10–8 M
N 9 1.0 10–9 M 1.0 10–5 M 5
M 10 1.0 x10–10 M
L 11 1.0 10–11 M 3
K 12 1.0 10–12 M 1.0 10–2 M
J 13 1.0 10–13 M 1.0 10–1 M 1
NaOH
Unit IV • Investigation IV-X
Making Sense
– How are pH and pOH related to each other mathematically?
Unit IV • Investigation IV-X
This box would show 1,000 H+ ions and 1,000 Cl– ions.
This box would show 100 H+ ions and 100 Cl– ions.
Key: H+ Cl–
pH = 4
Notes
pH = 5 pH = 6 pH = 7
(cont.)
Unit IV • Investigation IV-X
• pH = –log[H+]
• pOH = –log[OH–]
(cont.)
(cont.)
Unit IV • Investigation IV-X
• Sample Problem:– What is the pH of a solution with a
hydrogen ion concentration of 3.4 10–4 moles/ L?
(cont.)
(cont.)
Unit IV • Investigation IV-X
• Please be careful when entering scientific notation into your calculator—it is very easy to make a mistake. When entering 3.4 10–4, first enter “3.4”. Then press the button labeled “EXP” or “10X” or “EE”. Now enter –4, using the “+/–“ key, not the subtraction key. Never try to enter this number by pressing “X” and “10” and “–4”.
(cont.)
Unit IV • Investigation IV-X
Check-In
– What is the pH of a solution with [OH–] = 1.0 10–12 M?
Unit IV • Investigation IV-X
Wrap-Up– The relationship between pH and pOH of a
solution is expressed by the following: pH + pOH = 14.
– The relationship between [H+] and [OH–] in a solution is expressed by the following: –log [H+] + –log [OH–] = 14.
– The pH of a solution is logarithmically related to the concentration of hydrogen ion and can be calculated mathematically using the following equation: pH = log [H+]