Combustion
1. If you hold a long copper wire in a candle flame, copper wire gets red hot in the non - luminous part whereas it just gets blackened in the luminous part. Why? 2. Goldsmiths often use a mettalic blow to direct non luminous part of flame on gold to give shape to gold ornaments. Why? 3. You observe circular greyish black ring formed on the glass slide in which there is no deposition in the middle of the ring. Why? 4. Water should not be used to extinguish fire caused by electric short circuit. Justify your statement. 5. Two paper cups, one filled with water and other empty, are heated over a bunsen burner. Empty cup catches fire immediately whereas the other does not. Why?