CBSE Class 7 th Chapter: Physical and Chemical Change HOTs Questions 1. Why gas is released after opening Soda Water bottle? Ans: Soda water bottle contain CO 2 gas that released after opening the soda water bottle. 2. Why it is advised that spoon should not be placed in pickle Jar? Ans: Spoon is made up of metal that react with acid present in pickle and form another salt and spoil the pickle .Hence it is advised that spoon should not be placed in pickle Jar 3. Why does apple Slice got brown color if kept in air for long time? Ans: Apple Slice got brown color if kept in air for long time because it react with oxygen and form layer of oxide which spoil the apple .This is called rancidity. 4. How is Scratch resistant material is made? Ans: Scratch resistant material is made by mixing two or more metal called Alloy like steel. CBSE Class 7 th Chapter: Electric Current a
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