Science
(a) Name two metals which react violently with cold water. List any three observations which a student notes when these metal are dropped in a beaker containing water.
(b) Write a test to identify the gas evolved (if any) during the reaction of these metals with water.
Metals & Non-Metals
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Answer
(a) The two metals which react violently with cold water are sodium (Na) and potassium (K).
Three observations when these metals are dropped in water are:
- Fizzing and hissing due to rapid evolution of hydrogen gas.
- The metal piece moves rapidly on the water surface and melts.
- The reaction produces heat, making the water alkaline due to formation of metal hydroxide.
(b) The gas evolved is hydrogen which can be tested by bringing a burning matchstick near the mouth of the test tube.The gas burns with a ‘pop’ sound, confirming the presence of hydrogen.
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