ACID RAIN and pH
Despite its name, acid rain doesn’t always occur in the form of rain. In
parts of the world with wet weather, there is acid rain, acid snow, and
acid fog. In parts of the world with dry weather, there is acid gas and
acid dust.
Acid rain is mainly caused by pollutants (like carbon dioxide, carbon
monoxide, hazardous air pollutants, etc) being released into the air.
Most of the pollutants are from cars - they release harmful smoke into
the air, which can cause acid rain. Coal, oil, and gasoline also cause the
pollutants.
Acid rain is very harmful to the
environment - it can make living
things (both in the water and on
land) die. Acid rain affects human
health. Breathing and lung
problems have been linked to acid
air pollution. Also, everything that
we eat, drink, and breathe has at
one time come into contact with
acid rain pollutants.
Tree branches damaged by acid rain
Today’s Lab
All “rainwater” contains some level of acidity. Acidity is measured by
pH, which stands for potential of hydrogen. pH is measured on a scale
from 0 to 14. The lower the number is on the pH scale, the more acidic;
the higher the number, the more basic. Pure water is neutral with a pH
of 7.0. When chemicals are mixed with water, the mixture can become
either acidic or basic. Normal rainwater has a pH of 5.6. When the pH
level of rainwater goes below 5.6, it is considered acid rain.
In today’s activity, you will use a sensitive pH meter and litmus paper
to measure the pH of melted snow from our area, as well as tap water,
filtered (drinking) water, and ultra pure (laboratory) water. You will
then predict and measure the pH of some commonly used household
items.
Results Tables
Table 1: Testing the pH of different samples of water
Water
Sample
pH
(litmus paper)
pH
Difference
(pH meter)
Acid or
base?
Melted
snow
Tap water
Filtered
(drinking)
water
Ultra-Pure
(lab) water
Table 2: Testing the pH of compounds that we use everyday
Sample
Predictions
pH
Orange
Juice
Soda
Rubbing
Alcohol
Acid
or base?
Observations
pH
(litmus paper)
pH
(pH meter)
Difference
Acid
or
base?