Types of Matter Transformation

Matter has the ability to change from one form to another. Cooking takes advantage of this property by using heat and time to convert raw food into an enjoyable and edible form. As we mix the ingredients for a meal, we place chemicals together that have the ability to react to form a pleasant tasting substance. The rate at which a substance changes form is called reactivity. Some substances react very easily with other materials. Other substances have the tendency to remain in their present state. We use this property to determine how long and at what temperature to cook our food. Some foods require very little preparation time, while others can take all day to prepare. When we cook our food, we rearrange atoms and molecules. As the saying goes, it makes our food "nutritious and delicious".

Any time we cook our food, we are carrying out chemical reactions. A chemical reaction occurs when substances exchange or rearrange atoms to form a new substance. When we place cake batter into the oven, it goes in as a liquid mixture. During the cooking process, we add energy to the mixture which causes a chemical change to occur. During a chemical change, atoms rearrange to form new substances completely different from the original. When we bake a cake, a chemical change occurs where the atoms in the mixture rearrange themselves into a fluffy solid. This fluffy solid is what we love to eat.....cake!

There are several factors that determine how readily a substance will undergo a chemical change. The arrangement of electrons in an atom is one of the greatest factors that determine whether an atom is reactive or not. If an atom has too few electrons or too many electrons it will react in order to become stable. As a general rule an atom is stable when it has 8 electrons in its outermost energy level. If an atom already has eight electrons in its outer shell it is nonreactive and will not go through chemical changes under normal conditions. If you will look at the diagram below you can see how an atom can reach a stable state by reacting with another atom.

gif of atom from Na reacting with F

Another factor that determines if a substance will react is the amount of energy a substance contains. Most reactions occur where the energy contained by substances after the reaction is lower than before the reaction. This is not always the case, but is the natural tendency without outside intervention by a living thing or the addition of thermal energy from the Earth/Universe. Think of a fire used for cooking a marshmallow. The energy contained in the wood is released through a chemical reaction where the ash, carbon dioxide and water have less energy than the wood did before the fire. There are other factors that determine reactivity, but they are less important and more in depth than we will discuss here.

When we are cooking not only do we have to take into account the chemical changes that occur to our food, but we also need to be aware of safety issues as well. Some compounds are combustible and can start a fire if left unattended. One of the most dangerous items used in the kitchen is cooking oil. If cooking oil comes in contact with the stove burner a grease fire can result. These fires are especially dangerous because they can spread very quickly. If water is placed on the fire, the grease will float on the water's surface and remain on fire. This allows the grease to spread over a larger area and the fire can burn out of control and spread to other parts of the home. So remember, don't put water on a grease fire.

As you can see, we use chemistry when we prepare a meal. We take advantage of chemical reactions, chemical changes, energy changes and phase changes when we cook our food. Without these changes our food would have little taste and we would have few choices when it comes to eating. Science is all around us, and the better we understand the processes that shape our world, the more we can use them for our benefit.

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