Learning Objectives
- Define chemical change.
- Give examples of chemical changes.
Do you like to cook?
Do you like to cook?
Cooking is a valuable skill that everyone should have. Whether it is fixing a simple grilled cheese sandwich or preparing an elaborate meal, cooking demonstrates some basic ideas in chemistry. When you bake bread, you mix some flour, sugar, yeast, and water together. After baking, this mixture has been changed to form bread, another substance that has different characteristics and qualities from the original materials. The process of baking has produced chemical changes in the ingredients that result in bread being made.
Chemical Change
Most of the elements we know about do not exist freely in nature. Sodium cannot be found by itself (unless we prepare it in the laboratory) because it interacts easily with other materials. On the other hand, the element helium does not interact with other elements to any extent. We can isolate helium from natural gas during the process of drilling for oil.
A chemical change produces a different materials than the ones we started with. One aspect of the science of chemistry is the study of the changes that matter undergoes. If all we had were the elements and they did nothing, life would be very boring (in fact, life would not exist since the elements are what make up our bodies and sustain us). But the processes of change that take place when different chemicals are combined produce all the materials that we use daily.
One type of chemical change (already mentioned) is when two elements combine to form a compound. Another type involves the breakdown of a compound to produce the elements that make it up. If we pass an electric current through bauxite (aluminum oxide, the raw material for aluminum metal), we get metallic aluminum as a product.
Figure 2.16
Electrolytic production of aluminum.
However, the vast majority of chemical changes involve one compound being transformed into another compound. There are literally millions of possibilities when we take this approach to chemical change. New compounds can be made to produce better fabrics that are easier to clean and maintain; they can help preserve food so it doesn’t spoil as quickly; and, we can make new medicines to treat diseases – all made possible by studying chemical change.
Summary
- A chemical change produces a different materials than the ones we started with.
Practice
Questions
Use the link below to answer the following questions:
http://chemistry.about.com/od/lecturenotesl3/a/chemphyschanges.htm
- Where do chemical changes take place?
- What does a chemical change produce?
- What are physical changes concerned with?
Review
Questions
- What is a chemical change?
- List three types of chemical changes.
Glossary
- chemical change: A change that produces matter with a different composition.
