Lesson 4

1 What did you do last time? 2 nucleus H2 hydrogen protons O2 electrons PRINT the word next
to the image on the next slide.
ChemPlus - L4 o2 hyd pro h2 ele nuc
4 pH and Naked Protons If you strip the electron from a hydrogen atom,
what is left in the center?

A “naked” proton!

The proton is no longer
together with its electron.

These protons are called
hydrogen ions.

What charge would a loose proton have?

because protons
are positively charged: H+.
hydrogen* has
ONE proton,
ONE electron
and NO neutrons!
* To be precise, there ARE forms
of hydrogen that DO have neutrons.
These are called isotopes.
H+ I’m a
hydrogen ion.
I want my
electron back!
5 The higher the concentration
of hydrogen ions,
the more acidic the solution.
You probably know that battery acid
is a strong acid and is poisonous!

It is so strong, it can burn a hole through a table top, solid steel,
or your clothes and skin.
Acidity is measured in terms of pH.
Let's explore pH.
6 Vinegar is acidic. Many sour candies
are very acidic.
Citrus fruits such as oranges,
lemons and grapefruits are acidic.
Do you realize that you like to drink
and even eat some MILD and not so mild acids?
Acidic foods are SOUR to your taste buds.
Taste buds are good at judging acidity.
The more sour a food is, the more acidic it is.
7 Try ranking these food items it terms of acidity.
Which do you think is the most SOUR or acidic?
What order would you put them in? Write it down.
Now test your predictions!
8 Find these items
in the kit.
pH and Naked Protons!
pH Standard Chart
(at the center
of the book)
along with the
pH Table of Results.
small cups
You may need help with the hot tea. sour candy
permanent marker Find the items around
your home.
pH strips
9 Label one cup
H2O for water.
Begin by testing the pH of water. Put a pH
indicator strip
into the water.
1 2 3 Pour in
the water.
Wait for the color changes to stop. Match the colors on the strip
to the colors on the pH Standard Chart.
The number above the best color match is the pH.
The stick shown here has a pH of 6.
4 pH 6
10 The pH of distilled water is neutral -- a pH of 7.
A pH of less than 7 means your water is acidic.
Greater than 7 means the water is basic or alkaline.
5 Alkaline water - a fad without data. What was the pH for tap water?
Record the pH for water on the pH Table of Results.
11 Now measure the pH of other liquids. Label each cup
and add the liquid
or powder, as shown.
DO NOT MIX the Liquids together!
Check the pH of the sour candy by soaking
the candy in water.
Add water and stir.
12 Use a fresh indicator stick
to test the pH
of each liquid.
Leave the strip in until
the color changes stop.
9 8 7 While each strip is still moist,
match the colors on the strip
to the colors on the standard chart.
Record your results
in your pH Table of Results.
pH 2
13 Now think about your results.
A pH of 7 is neutral.
A pH that is less than 7 is acidic.

The lower the pH, the more acidic the liquid.

Which solutions were the most acidic?
Which solution(s) had a pH greater than 7?
It was basic or alkaline, not acidic.

A pH of 6 is ten times more acidic than a pH of 7.
A pH of 5 is ten times more acidic than a pH of 6
and 100 times more acidic than 7.
A pH of 1 is a lot more acidic (1,000,000 times) than a pH of 7.

Discard all your solutions. Rinse and save the experiment cups.
Acidic Basic Neutral
14 A Colorful Magic Trick with Acids and Bases 15 So what do these acids have to do with hydrogen,
the first element in the periodic table?
hydrogen ion All of the acids that you worked with
(tea, orange juice, lemon juice and sour candy)
have hydrogen ions.
These hydrogen ions cause the acidity of the solutions.
The more ions there are, the more acidic the solution is.
Remember, the symbol for the hydrogen ion is H+.

These stripped down protons seek electrons!
They “love” their missing electrons.
They are called electrophilic.
H+ H+ H+ H+ H+
16 Many living organisms depend
on a narrow range of pH to survive.
Freshwater fish prefer slightly acidic
to neutral pH (6-7 pH) and
can tolerate wider variations in pH
than can saltwater fish.
You can turn a pink hydrangea
to blue by making
the soil acidic.
Some plants, such as camellias,
azaleas and rhododendrons,
prefer an acidic soil
with a pH of less than 7.
Most saltwater fish
require a pH of about 8.1.
Much lower or higher
and they will die!
17 Climate Change
is impacting the pH of Earth's oceans!
REMEMBER: pH is a logarithmic scale! Ocean acidification due to climate change,
affects phytoplankton and zooplankton.
They cannot survive small changes in pH.
These tiny plants and animals form the base
of the marine food web.
Without them, the food chain
in the ocean collapses.

Ocean acidification has caused
MASS EXTINCTION events in the past.
It is causing another one now.
18 The element with
one proton is called
Acids have a
pH below what
Does a hydrogen
ion have a charge
What are the characteristics of hydrogen at room temperature 1 2 3 4 5 When was
hydrogen formed
a colorless, orderless, highly flammable gas and a diatomic molecule, H2 hydrogen seven YES. H+
a positive charge
shortly after the big bang