MEDIUM
Lower Secondary Stage 7
IMPORTANT
Earn 100

In areas of hard water, limescale is deposited inside kettles when the water is boiled. Vinegar or lemon juice can be used to remove the limescale. What does this tell us about the limescale? 
 

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Important Questions on Acids and Alkalis

MEDIUM
Lower Secondary Stage 7
IMPORTANT
Cambridge Lower Secondary Science Stage 7 : Workbook>Chapter 7 - Acids and Alkalis>Exercise 2>Q 4
John has just been stung by a bee. He wants to put some vinegar (mild acid) on it to ease the pain but his Mum says no, that will make it worse. She says he should use baking powder (mild alkali). 
Explain why Mum is correct. 
MEDIUM
Lower Secondary Stage 7
IMPORTANT
Cambridge Lower Secondary Science Stage 7 : Workbook>Chapter 7 - Acids and Alkalis>Exercise 2>Q 5
If alkali A has a pH value of 13 and alkali B has a pH value of 9, explain which is most likely to be used in indigestion tablets as a remedy for excess stomach acid.
EASY
Lower Secondary Stage 7
IMPORTANT
Cambridge Lower Secondary Science Stage 7 : Workbook>Chapter 7 - Acids and Alkalis>Test-style questions>Q 6

Indigestion is caused when stomach acid irritates the lining of the food pipe. 

Which remedy would you use to cure it? 

EASY
Lower Secondary Stage 7
IMPORTANT
Cambridge Lower Secondary Science Stage 7 : Workbook>Chapter 7 - Acids and Alkalis>Test-style questions>Q 6
Indigestion is caused when stomach acid irritates the lining of the food pipe. Use your knowledge of acids and alkalis to explain why antacids are taken as remedy.