There are several reasons why chemicals are placed in food. Firstly, it is to improve the product to the eye, and this is achieved via the use of colourings which encourage people to purchase food that may otherwise not look tempting to eat. Another reason is to preserve the food. Much of the food we eat would not actually last that long if it were not for chemicals they contain, so again this is an advantage to the companies that sell food as their products have a longer shelf life.