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SCIPAD - BIG IDEAS - BOOK 2
BASIS OF CHEMICAL REACTIONS
Useful Neutralisation
If you have ever had indigestion then you will know how useful neutralisation reactions can be.
Indigestion is caused by acid rising up into your oesophagus. Your stomach is protected from
the acid because it produces a protective mucus to prevent the acid from getting to the cells
of your stomach wall. However, the oesophagus does not produce any protective mucus so the
acid burns the lining of your oesophagus and can lead to the formation of ulcers. The pain from
indigestion can be treated quickly by using an indigestion (antacid) tablet. ‘Antacid’ comes from
the term ‘anti-acid’ and is another word for alkali. In other words you take a tablet containing
an alkali to neutralise the excess acid in your stomach and oesophagus. However, you definitely
do not want your stomach to become completely neutral because it would stop the process of
digestion. The tablets contain enough alkali to neutralise just the excess acid.
1. What causes indigestion? 

2. Outline why the stomach is not affected by the acids it contains. 

3. Describe the origin of the term ‘antacid’. 

4. Is an antacid tablet acidic or basic? 
5. Explain why it is important that antacid tablets contain only enough base to neutralise the
excess acid. 


The pancreas releases a fluid at the junction of the stomach and small intestine. This fluid prevents
stomach acid from burning the small intestine.
6. Outline where on the pH scale you might expect to find this substance. 
7. What is the name of the chemical reaction that occurs between stomach acid and this
pancreatic fluid. 

Oesophagus
Stomach
Small intestine
Fluid from the
pancreas enters
the small intestine
Pancreas
Acid rising up the
oesophagus causes
indigestion or “heartburn”
Location of the oesophagus,
stomach and pancreas
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