Des's answer to Jane's Secondary 4 Chemistry Singapore question.

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Des
Des's answer
9 answers (Tutor Details)
1st
oil prevents air and thus oxygen from reaching your paper clip, causing oxiddisation and rusting.

for experiments, you need to have 1 control test i.e. the test tube with air and oxygen, and another test tube without air and oxygen with all other conditions kept the same. for this case it will be the water.