Sarah McBride and Regan Bain, of Green Island Primary School, asks :-
Can Oil and Vinegar explode?
David McMorran, a chemist at Otago University, responded.
Most explosions are a particular type of chemical reaction which has to have three properties: it must be an exothermic reaction, which means that it must produce lots of heat when it happens; it must make a gas as a product of the reaction; and it must be a very fast reaction. For example, when dynamite explodes, a chemical compound called nitroglycerine (a solid) reacts, producing nitrogen gas. In a gas, the molecules lie much further apart from each other than they do in a solid. So gases need a lot more space than solids and the amount of space they need increases as the temperature increases. When a stick of dynamite explodes, the heat produced by the reaction is so much that the temperature rapidly increases to about 5000 degrees Celsius. The result is that the nitrogen gas formed in the reaction needs 23 000 times the amount of space taken up by the original stick of dynamite. The gas making this much room for itself is what causes things to 'blow up'.
When you mix vinegar with baking soda, a chemical reaction happens which produces a gas, carbon dioxide. If you do this reaction inside a zip-lock bag then the gas produced will soon cause the bag to pop. However, this reaction doesn't meet our definitions of an explosion because the reaction does not give out much heat and it is relatively slow. Oil and petrol can explode under certain conditions. The engine in your car works by small petrol explosions forcing the pistons up and down. The explosion is caused by a spark from the spark plug and a number of different gases are produced by the explosion, including carbon dioxide. Mixing cooking oil with vinegar wont, to my knowledge, produce an explosion but can make a tasty vinaigrette.