Chemical Changes in Matter
Compare a tarnished silver spoon with a clean, polished spoon. The tarnished spoon is dull and has a dark coating. On the other hand, the polished spoon is shiny and bright.
When silver reacts with sulfur in the air, a new kind of matter is formed that has different properties from the original silver. The ability to react with sulfur to form new matter is a chemical property of silver.
You have learned that a chemical property describes how matter reacts with other kinds of matter. Some other chemical properties of matter are the ability to burn, rust, and explode.
A piece of wood cannot rust, but it can burn. The ability to burn is a chemical property of wood, paper, and some other kinds of matter. Compare the paper before and after it has burned. You probably notice a difference. Burning has changed the chemical properties of the paper.
The burned part of the paper is no longer paper. It is a different kind of matter. A chemical change has taken place. A chemical change transforms matter into one or more new kinds of new matter after a chemical reaction. It is a change where the type of matter changes. A chemical change is different from a physical change, they are very opposite. In a chemical change, the original matter and the new matter have a different properties, it is not the same properties.
Rusting is a chemical change. Iron rusts when it come in contact with air and water. The new matter that forms is softer than iron and is orange-colored.
Reminder: Chemical changes produces new substances. These substances have different properties than the original ones. Oftentimes you can see, hear or even smell the formation of new substances once a chemical change occurs. It is a permanent change, we cannot reverse it back.
Signs of a chemical change:
- change in color - like bleach whitens a piece of cloth.
- tarnishing - it is the corrosion of a metal which causes a change in color. Like example, A metal has been covered in layers of rust. And it is turned into color reddish.
- appearance of bubbles - when a chemical change occurs and bubbles form. Like example, mixing baking soda and vinegar.
- percipitate - it is a solid formed from the chemical reaction of some solutions. Like example, "soap scúm" it has formed from solutions of soap and water. When a sink is not cleaned properly, it may develop a sticky white layer, called "soap scúm."
- release of light and heat - like example a burning candle, it produces a hot flame. The heat and the light comes from the combination of atoms in the candle and the wick with oxygen from the air. If a chemical reaction releases energy, then reversing that chemical reaction will absorb energy.
Chemical changes occur everywhere. Useful chemical changes take place during the burning of fuel and cooking.
Useful of Chemical Changes
Chemical changes are an important part of life because they take place in the human body. One cannot stay alive without these changes. For example, when you eat, a series of chemical changes begins. Inside your body, the food is changed chemically into new matter that your body can use for energy and growth. The cooking of food also causes chemical changes.
Plants use a series of chemical changes. They use energy from sunlight to make food. Cars and buses move because of chemical changes. When gasoline is bumed in the engine, chemical changes release energy. Exploding fireworks with colorful display also happen because of chemical changes.
For more info:
What is Physical Change?
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