Questions:
Topic / Objective: Acids and bases
Name:
Essential Question: What is the difference between an
acid and a base?
Class:
Date:
Notes:
Quickwrite: What does an acid do?
-
Acids are substances that are:
o Corrosive (react with a solid substance such as a metal and “eat” them
away).
o Usually have a sour taste
o Aqueous
o The stronger an acid the more corrosive it is
-
Bases are substances that are:
o Corrosive (react with a solid substance such as a metal and “eat” them
away).
o Usually have a bitter taste
o Tend to be “soapy/slippery”
o Also called an alkali or an alkaline solution.
o Aqueous
o The stronger an acid the more corrosive it is
Students are to watch YouTube video “Coke Cans in Acid and Base - Periodic Table of
Videos”
https://www.youtube.com/watch?v=WnPrtYUKke8
-
You can describe how acidic or basic a substance is by using the numbers on
the pH scale.
The pH scale ranges from 0 to 14.
Low pH numbers (less than pH 7) mean that substances are acidic, the lower
the number, the stronger the acid.
High pH numbers (more than pH 7) mean that substances are basic, the higher
the number, the stronger the base.
If a substance has a pH of 7, it is said to be neutral and is neither acidic nor
basic. Pure water has a pH of 7.
Students are to glue pH chart (below) into their Cornell notes
-
-
An indicator is a substance that, once added into a solution it causes a change
in colour. That colour is then compared to a pH chart to find the pH of that
solution.
The type of colour change and at what pH the colour change occurs depends
on the type of indicator
o E.g. Litmus which turns red in an acid and blue in a base, and
bromothymol blue, which turns yellow when added to an acid and a
bluish-purple when added to a base.
o Universal indicator is a mixture of many indicators and has a pH chart
showing a rainbow colour arrangement.
Students complete practical “measuring pH”
Measuring pH
Purpose: To determine whether a substance is an acid and a base
Materials:
-
Strips of blue litmus paper
Strips of red litmus paper
Dropper bottle containing bromothymol blue indicator
Dropper bottle containing universal indicator
pH chart
Variety of different substance each poured into two 100mL beakers
Procedure:
-
In one beaker insert the litmus paper, record your observations in Table 1.
In that same beaker ass a couple of drops of bromothymol blue indicator, record
your observations in Table 1.
In the other beaker add a few drops of universal indicator and using the universal
indicator pH record your observations in Table 1.
Table 1. Observations and pH of certain substances
Chemical
name
Blue Litmus
paper
Colour Acid or
base?
Red Litmus paper
Colour
Acid or
base?
Bromothymol
blue
Colour
Acid
or
base?
Universal indicator
Colour
Acid
or
base?
pH