Physics: Understanding the Properties of Matter and Energy
PHYSICS UNDERSTANDING THE PROPERTIES or MATTER AND ENERGY motion A bird flying through the air and an arrow shot out of a bow both have kinetic energy Potential energy is energy that is stored up but not yet used A rubber band that has been stretched out has potential energy As soon as it is let go that energy becomes kinetic because it is in motion The water behind a dam also has potential energy which becomes kinetic energy when water released from a dam rushes out In this book you will learn about the fun damentals of matter and energy and how physicists have discovered the basic building blocks of the universe and their properties You will also learn about the prominent scientists who have made these discoveries tested theo ries and given us a wider view of the known universe all by looking at its most basic parts 10
CHAPTER 1 WHAT IS MATTER n electron a grain of sand an ele phant and a giant quasar at the edge of the visible universe all have one thing in common they are composed of matter Matter is the material substance that makes up the physical universe A beam of light the motion of a falling stone Large elephants and the tiny dust specs that they kick up are all made of the same substance matter Johan Swanepoel Shutterstock com 11
PHYSICS UNDERSTANDING THE PROPERTIES or MATTER AND ENERGY and the explosion of a stick of dynamite all have one thing in common they are expres sions of energy Energy and matter together form the basis for all observable phenomena THE STATES OF MATTER Most of the matter that people ordinarily observe can be classified into one of three states or phases solid liquid or gas Solid solid gas ice water vapor liquid water cyclopaedia Britannica no Water exists in the three basic states of matter as ice water and vapor Encyclopaedia Britannica Inc 12
WHAT IS MATTER matter generally possesses and retains a def inite size and shape no matter where it is situated A pencil for example does not change in size or shape if it is moved from a desktop and placed upright in a glass A liquid unlike a solid assumes the shape of its container even though like a solid it has a definite size or volume A pint of water changes its shape when it is poured from a glass into a bowl but its volume remains the same A gas expands to fill the complete volume of its container At a given temperature and pressure a sub stance will be in the solid liquid or gaseous state But if the temperature or the pressure changes its state may also change At con stant atmospheric pressure the state of water for example changes with changes in tem perature Ice is water in a solid state If it is removed from a freezer and placed in a warm pan the ice warms up and changes to a liquid water If the pan is then placed over a hot fire the water heats up and changes to the gaseous state steam Most substances can exist in any of the three states provided that they do not decom pose chemically as sugar for example often does when it is heated in air Oxygen must be cooled to very low temperatures before it becomes a liquid or a solid Quartz must be 13
