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?


The Big Question

– What are some characteristics of solutions that are acidic, basic, or neutral?


You will be able to:

• Describe the differences among acidic, basic, and neutral solutions.


– Indicators: A set of substances that respond to other substances with vivid color changes.

Notes


Activity

• Purpose: This activity will introduce you to a special category of solution.

(cont.)


• 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.)


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


1470

(cont.)

(cont.)


Observations when added to CaCO3

water

stomach acid

vinegar

drain cleaner

(cont.)


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.


• 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


– 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.)


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.


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.


Lesson 2:Watered Down


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?


The Big Question

– How does dilution affect the acidity or basicity of a solution?



• Explain how dilution affects the concentration and pH of a solution.


Activity

• Purpose: In this activity you will examine the effect of concentration on acidity and basicity of solutions.

(cont.)


• 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.)


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


Data Table for dilution of 1.0 M NaOH


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


Data Table for dilution of 1.0 M NaCl


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


Making Sense

– What does concentration have to do with the acidity or basicity of a solution?


1470

More H+ More OH–

pH scale

Notes

(cont.)


• 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.)


• HA H+ + A–

• XOH X+ + OH–

(cont.)


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?


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.)


– 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.


Lesson 3:pHooey!


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.)


– What do you think pH really represents?

– How does the concentration of the solutions relate mathematically to the pH of the solutions?

(cont.)


The Big Question

– How does pH relate to the concentrations of acidic and basic solutions?



• Find the pH of a solution if you know the concentrations of hydrogen or hydroxide ions that it contains.


Activity

• Purpose: You will explore the relationship between pH, pOH, [H+], and [OH–].

(cont.)


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


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


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


Making Sense

– How are pH and pOH related to each other mathematically?


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.)


• pH = –log[H+]

• pOH = –log[OH–]

(cont.)

(cont.)


• Sample Problem:– What is the pH of a solution with a

hydrogen ion concentration of 3.4 10–4 moles/ L?

(cont.)

(cont.)


• 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.)


Check-In

– What is the pH of a solution with [OH–] = 1.0 10–12 M?


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+]

toxins unit – investigation iv lesson 1: heartburn

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