4 A crystal is a certain type of solid object It is a form of matter Scientists describe mat ter or everything that can be seen according to the way it is made All matter is made up of tiny parts called atoms and molecules If all those parts are arranged in a regular repeating pattern then the object is a crys tal The outsides of crystals have a regular pattern of flat surfaces that meet in sharp corners WHAT ARE CRYSTALS Different substances form different crystal shapes But all crystals of the same substance have the same shape
5 Most solid matter that is not alive is made up of crystals Common substances such as sugar and salt are made of crystals So are metals such as gold silver copper and iron Diamonds emeralds and other gems precious stones are also crystals Some objects are not made of crystals however Glass is one such example Its molecules are not arranged in any particular pattern Atoms are tiny particles that are the basic building blocks of all matter Atoms can be combined with other atoms to form molecules but they cannot be divided into smaller parts by ordinary means VOCABULARY Crystals include lovely precious stones also called gems such as diamonds and emeralds
6 Matter exists in several different forms called states The three most familiar states are solid liquid and gas Mat ter in a solid state has a set size and shape Those do not change easily In the liquid state matter has a set size or amount However its shape depends on its container For example milk changes shape when a person pours it from a carton into a glass But the amount of milk stays the same A gas does not have a set size or a set shape It can expand to fill a larger container or can be squeezed into a much smaller container The states of matter include solid liquid and gas Matter can change from one state to another such as by freezing or melting
7 Most crystals form when a liquid changes to a solid Water freezing is a familiar example of this process As water freezes its mol ecules line up and join to form ice crystals Snowflakes are collections of ice crys tals Crystals also form when a liquid with mat ter dissolved melted in it dries up For example when salt water dries up salt crystals form Many crystals behave like butter They are hard at low temperatures but turn soft at higher temperatures Why do you think that is THINK ABOUT IT A snowflake is made up of a collection of ice crystals Each snowflake is different but most have six points or six sides
