a) Mention the pH range within which our body works. Explain how antacids give relief from acidity. Write the name of one such antacid.
(b) Fresh milk has a pH of 6. HOW will the pH change as it turns to curd ? Explain your answer.
(c) A milkman adds very small amount of baking soda to fresh milk_ Why does this milk take longer time to set as curd ?
(d) Mention the nature of tooth pastes. How do they prevent tooth decay?
CBSE Class X Science LA (5 Marks)
Answers
7.0-7.8 is the ph range in which human body works.
The answers are as follows:
Explanation:
(a) The pH of the stomach is 2. Antacids are the chemicals which acts like a base and they neutralize the acidity in the stomach.
Sodium hydrogencarbonate is a kind of antacid.
(b) pH of the milk decreases when it is turned into curd. This is due to increase in the acidity of the milk because of the lactic acid producing bacteria Lactobacillus.
(c) Sodium hydrogen carbonate or baking soda is basic in nature thus it will increase the pH of the milk thus acid producing bacteria in the milk will not be able to produce acid in its presence so early. Thus it will take time to bacteria to turn the milk into curd.
(d) The nature of toothpaste is basic. They neutralize the acid produced due to food in mouth hence prevent tooth decay due to these acids.
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