What happens when food materials containing fats and oils are left for a long time? List two observable changes and suggest three ways by which this phenomenon can be prevented.

What do you mean by rancidity? Mention any two ways by which rancidity can be prevented.

(a) Define corrosion, what is the nature given to corrosion of iron ? (b) Name the colour of coating formed on silver and copper when exposed to air. (c ) List two damages caused by corrosion and suggest, how these can be prevented.

Which of the following cannot be used to prevent food containing fats and oils from becoming rancid?

What is tooth enamel chemically ? State the conditions when it starts corroding. What happens when food particles left in the mouth after eating degrade ? Why do doctors suggest use of tooth power/tooth paste to prevent tooth decay ?

Consider the word W = COMMISSIONER Find (i) Number of 5 letters word containing two vowels and three consonants. Number of ways in which all the letters of the word W can be arranged if alike letters are together but seperated from the other alike letters (iii) Number of ways in which letters of the word W can be arranged without changing order of alike letters.