What Is Chemistry C hemistry is one of the major branches of science People who work in chemistry are called chemists Chemists study the substances that make up matter Matter is everything that takes up space in the universe Matter includes living things such as a dog or a person and nonliving things such as a book or a chair Chemists also study the changes that take place when substances are combined These changes are called chemical reactions In addition chemists create new substances They have made plastics fibers This chemist uses the tools in her laboratory to combine substances and observe when chemical reactions occur 4
Plastic is a human-made material There are many types of plastic Most are made from chemicals that come from petroleum or coal building materials medicines and many other substances that are useful in everyday life Like the substances chemists work with and study a career in chemistry can take many different forms THIN K ABO UT IT Chemists have created many of the materials that we use in our lives every day Look around you What substances or materials do you see that were made possible by the work of chemists 5
Elements and Compounds T he basic substances that chemists study are called chemical elements Chemical elements are the building blocks for all matter The smallest unit of an element is called an atom Each element is made up of only one type of atom Chemical reactions involve atoms or groups of atoms When two or more atoms combine they form a molecule Each element has certain properties When elements are combined they form a new substance with its own properties A substance formed in this way is called a compound Baking soda and vinegar are both compounds When they are combined a chemical reaction occurs 6
Table salt is a chemical compound It is made up of equal parts of the elements sodium and chlorine There are a little more than 100 known elements There are millions of compounds though A major part of a chemist’s job is to study the way elements and compounds react and then develop new ways to use them THIN K ABO UT IT Water is a compound made up of two elements called hydrogen and oxygen How is water affected by high heat How is it affected by extremely cold temperatures 7
