"Natural Science 4" is an interactive encyclopedia that includes scientific information in the understanding of fourth grade students, wonderfully illustrated and animated.
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* Chapter 4 Lesson 23 *
* Burning, rusting, spoiling, rotting, baking *
Wherever we are and whatever we do, the things around us are constantly changing. Whether we're talking about plants sprouting, growing and developing, wood burning in a fireplace or a carrot being nibbled by a rabbit, the things around us change shape, color, size and structure. They absorb or release energy, and even create new substances.
Most of the transformations that the bodies around us undergo fall into two broad categories: physical and chemical. In other words, physical and chemical transformations are two ways in which matter changes.
In the case of physical transformations, the appearance changes, but the substance remains the same. Tearing a paper, inflating a balloon, chopping meat, freezing water or melting snow are physical transformations.
In the case of chemical transformations, matter changes.
To better understand the two types of transformations, we will start by making a cake. First, we will separate the egg whites from the yolk, whip the egg whites into foam and mix the egg yolks with sugar well. The transformations can be easily seen. Then, we will mix all the necessary ingredients to obtain the composition of a top. Even though separating the ingredients after mixing them is practically impossible, all the transformations so far are physical. But once the top is placed in the oven for baking, a chemical transformation takes place. The composition in the oven absorbs heat. It changes its consistency, color and taste, spreading a pleasant smell. The transformations that occur are not reversible. You can't turn a cake top into the composition you had before you put it in the oven. So baking is a chemical process.
What kind of transformation do you think happens when cotton candy is made? What about caramelized sugar?
Chemical transformations occur when the particles of one or more substances rearrange to create a new substance.
For example, when you light a match stick, the wood will burn and turn to ash. Ash is another substance, totally different from wood. As with baking, burning is an irreversible chemical process. By burning, the wood changes its structure, color, consistency, smell and gases, harmful to the environment, are released. Energy is also released during this process, in the form of heat and light.
In everyday life, chemical transformations are encountered at every turn. When an iron object is left for a long time under the action of air and moisture, it is covered with a layer of a reddish-brown substance called rust. Rusting is the oxidation of iron. The more moisture in the air, the faster the rusting process. Through rusting, the shape and quality of materials containing iron are affected. To protect against rust, these materials must be painted or coated with a layer of oil.
Dry leaves, fruit, animal and vegetable remains gradually decompose under the action of air, moisture and bacteria. The process is called putrefaction. Following this process, the soil is enriched with organic substances, necessary for plants. Compost is a natural fertilizer resulting from the decomposition of plants and animals after the end of their life cycle.
Also under the influence of environmental factors, foods undergo transformations that influence their quality. This process is called spoilage, and spoiled food becomes toxic to the body when ingested.
What are the foods that spoil the most easily? How can you prevent their rapid deterioration?