Class #100: Intro to Acids and Bases

Chemistry Class #100

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AIM: Students will understand that acids and bases
dissolve to form specific ions in solutions.

Class #100

Class #100 Do Now

A student adds solid KCl to water in a flask. The flask
is sealed with a stopper and thoroughly shaken until
no more solid KCl dissolves. Some solid KCl is still
visible in the flask. The solution in the flask is

A) saturated and is at equilibrium with the solid KCl

B) saturated and is not at equilibrium with the solid KCl

C) unsaturated and is at equilibrium with the solid KCl

D) unsaturated and is not at equilibrium with the solid KCl

You will see and answer this question on the next slide!

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Multiple Choice

A student adds solid KCl to water in a flask. The flask is sealed with a stopper and thoroughly shaken until no more solid KCl dissolves. Some solid KCl is still visible in the flask. The solution in the flask is

• saturated and is at equilibrium with the solid KCl

• saturated and is NOT at equilibrium with the solid KCl

• unsaturated and is at equilibrium with the solid KCl

• unsaturated and is NOT at equilibrium with the solid KCl

​Intro to...

Common items that contain acids and bases

Acids

● Vinegar
● Lemon Juice
● Stomach acid
● Soda

Bases

● Baking soda
● Laundry Detergent
● Toothpaste
● Bleach

​

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Multiple Choice

One example of a common base is

• laundry detergent

• vinegar

• soda

• asparagus

Characteristic Properties of Acids

● Dilute solutions of acids (like vinegar,

lemon juice, etc.) have a sour taste

● Concentrated acids burn skin, eat holes

in clothing, and corrode metal

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Characteristic Properties of Bases

● Bases have a bitter taste

● Bases have a slippery or soapy feeling

● Strong bases can burn skin

● Bases cause acid- base indicators to

change color

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Multiple Choice

One characteristic of a base is that it tastes

• sweet

• salty

• sour

• bitter

Multiple Choice

If you touch something and it feels slippery or soapy, it is probably

• an acid

• a base

Acids and Bases cause acid-base indicators to

change color

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Remember how we saw that ionic compounds (salts)

break apart into positive and negative ions when

they dissolve in a solvent?

The word we use for breaking apart into
ions is “dissociation”

●

Example:

“Ionic compounds dissociate in water.”

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Electrolyte

A substance that dissociates into ions (particles with
electrical charges) when it is dissolved in water or body
fluids.

● Because of these negative and positive charges,

electrolytes can conduct electricity when dissolved in
water

Salts are electrolytes because they dissociate into ions when

dissolved in water

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Multiple Select

Which of the following are characteristics of electrolytes? PICK TWO!

• They always change the color of acid-base indicators

• They create ions in solution

• They conduct electricity in solution

• They are highly concentrated solutions

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Acids and Bases also dissociate into ions, just like Salts

…..let’s see how….

Table K: Common Acids

In your Chemistry Reference Tables

Table K: Common Acids

Hey, did you
notice that
the acids all

have H in their

formulas?

That must

mean

something,

right???

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​Circle the H at the

beginning of each

formula in your notes!

Multiple Choice

When we look at Table K in the Chemistry Reference Tables, we will find that the acids all have _____ in their formulas!

• C

• H

• Na

• Cl

Table L: Common Bases

Table L: Common Bases

Hey, did you
notice that
most of the
bases have
OH in their
formulas, and

the word

‘hydroxide’ in
their names?
That must

mean

something

too.

​That must

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​Circle the OH and the word "hydroxide" in the table in your notes!

Multiple Choice

When we look at Table L of Common Bases, most of the formulas contain _____.

• PO

• NH

• CrO

• OH

Acids produce H+ ions in solution

Acid molecules DISSOCIATE (come apart) in water
●

When they dissociate, this produces the
positive hydrogen ion

Example: Hydrochloric Acid

The HCl molecule dissociates in water
into a positive hydrogen ion (H+) and a
negative chloride ion (Cl- )

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Multiple Choice

An important characteristic of acids is that

• they dissociate to produce the negative Cl- ion in solution

• they can dissociate to produce different positive ions in solution

• they dissociate to produce the positive H+ ion in solution

• they can dissociate to produce different positive ions in solution

(Most) Bases dissociate in water to produce

hydroxide (OH –ions)

Example:
Sodium Hydroxide

The NaOH molecule
dissociates in water into
a negative hydroxide ion
(OH —)and a positive
sodium ion (Na+ )

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Multiple Choice

An important characteristic of bases is that

• they dissociate to produce the negative OH- ion in solution

• they can dissociate to produce different negative ions in solution

• they dissociate to produce the positive NH4+ ion in solution

• they can dissociate to produce different positive ions in solution

There are a couple of different scientific definitions of acids

and bases.

One of the first definitions was
developed by Svante Arrhenius, a
Swedish chemist.

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Arrhenius Acid: Substance whose water
solution contains the hydrogen ion as the
only positive ion.

Svante Arrhenius

** The H+ ion (which is just a
proton) often combines with a
water molecule to create H3O+.
This is called a hydronium ion.

H+ ion + water molecule hydronium ion

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Multiple Choice

According to the Arrhernius definition, an acid in solution

• must produce a positive ion

• must produce ONLY the H+ ion

• must produce a negative and a positive ion

Arrhenius Base:A substance that produces

hydroxide ions(OH- ) when dissolved in

water

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Multiple Choice

According to the Arrhernius definition, an acid in solution

• must produce a negative H ion

• must produce the positive NH4 ion

• must produce the negative hydroxide ion

Multiple Choice

Electrolytes are substances that dissociate into ions in solution. That must mean that

• acids are electrolytes, but bases are not

• bases are electrolytes, but acids are not

• both acids and bases are electrolytes

• neither acids nor bases are electrolytes

Some important words

We use the word acidic to
describe solutions
containing acids:

“Lemons are acidic.”

“This is an acidic solution”

We use the word “basic”OR the
word “alkaline” to describe
solutions containing bases.

“A solution containing NaOH is
basic.”

“Bleach is an alkaline
substance.”

Acidic Basic / Alkaline

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Multiple Choice

Baking soda is a common base. Another way to describe baking soda is

• Baking soda is soapy

• Baking soda is acidic

• Baking soda is alkaline

• Baking soda burns holes in clothing

Open Ended

Write two things you learned about acids, and two things you learned about bases.