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ExposeExciteIgniteMay2012

Mg ! Mg 2+ + 2e 2H2O +

Mg ! Mg 2+ + 2e 2H2O + 2e ! H2 + 2OH - Here's how 1. Remove the blade of the sharpener with a screwdriver. You may need a small pair of pliers to hold the screwdriver. Cut a 30 cm length of Nichrome wire and fold back to produce a double wire of 15 cm. 2. Insert the wire through the hole in the sharpener. Wind the wire tightly around the body and tie it up tightly (Figure 7.6). This is important as the sharpener has to hang in there as long as possible. Curl the other end of the double wire around the metal rod. 3. Add water to the glass flask until it is ! full. Position on the Figure 7.6 gauze above the burner and secure the flask with the retort clamp. Adjust the wire length so the sharpener is suspended about 2 to 3 cm above the water level (Figure 7.7). $ Figure 7.7 4. Heat the water to boiling point and turn down the burner heat slightly once the water starts boiling. 5. Ignite the gas torch, lift the sharpener from the beaker using the rod and strongly heat the sharpener while suspending it above the flask mouth (Figure 7.8). This is the activation energy phase. Keep heating, focusing on the bottom part of the sharpener as this is where you want the combustion to start. Heat until it starts shooting a 79

few magnesium sparks. This is the sign to lower the sharpener into the flask, check that the rod is well supported by the flask, close the gas supply and move back 3 meters. If after one minute the reaction does not start, approach and re-heat the sharpener. Heat here Figure 7.8 6. Once the glowing reaction starts there is no stopping it. There will be a quick build-up in intensity as the magnesium and hydrogen burn brightly in the steam above the water. As heat builds up the alloy will melt and drop into the water where the reaction will continue. Do not move closer, the H2 gas build-up may cause it to explode. 80 Figure 7.9