Chapter 1

 Chemistry is the study of matter and the transformations it can undergo  Matter is anything that occupies space  Chemistry is a central science because it touches all the other sciences  Basic research leads to greater understanding of how natural world operates  Applied research focuses on developing these applications for practical uses

 Science is organized body of knowledge about nature  Scientific hypothesis is a new idea to explain what we observe if, and only if, it can be tested  Not a hypothesis if not testable  Which statement is a scientific hypothesis? The moon is made of Swiss cheese Human consciousness arises from an essence that is undetectable.  A theory is a single comprehensive idea that is repeatable and explains a wide range of observations.  Not fixed  Can be changed as new information is gathered

 Examples: length, time, mass, weight, volume, energy, temperature, heat and density  Any measurement of physical quantity must have a number and a UNIT

 Mass is quantitative measure of how much matter a material object contains (in grams)  Mass is measure of object’s inertia which is the resistance of an object to a change in motion  Weight is gravitational force exerted on an object. Weight depends on location  Volume is the amount of space an object occupies(in liters or milliliters)

 Energy is capacity to do work (measured in joules or in U.S. calories)  Potential energy is stored energy  Kinetic energy is energy of motion Faster a body moves, the more kinetic energy  Chemical substances posses chemical potential energy which is energy stored within atoms and molecules

 Atoms and molecules are in constant motion  They possess kinetic energy  Average kinetic energy is directly related to how hot something is  When something gets warmer, the kinetic energy increases (particles move faster)  Quantity that tells us how warm or cold an object is relative to a standard called temperature

 Most substances expand when temperature is raised and contract when lowered  Increasing temperature makes particles move faster and are farther apart so the material expands  Lowering temperature makes particles move slower and get closer together so material contracts (gets smaller)  A thermometer uses this property of matter measuring the expanding and contracting of a liquid (usually alcohol)

 Scale based on 100 degrees between freezing point and boiling point of water  0 is freezing point  100 is boiling point

 Calibrated based on the motion of atoms and molecules  Zero degrees is the temperature where there is no atomic or molecular motion  Called absolute zero  -273°C = 0 K  Kelvin degrees are the same distance apart as Celsius degrees

 Temperature is measure of average amount of energy in substance not the total amount of energy  Total energy in swimming pool is boiling water is much more than a cup of boiling water even though both are at same temperature  Average molecular motion is the same in both water samples  More molecules = more total energy

 Heat is energy that flows from higher- temperature object to a lower-temperature object  The greater the temperature difference between two bodies, the greater the rate of heat flow  Heat is a form of energy so unit is joule

 Matter has physical forms called phases  Solid has definite shape and volume  Not compressible  Liquid has definite volume but takes the shape of its container  Not compressible  Gas has no definite volume or shape  Easily compressible  Diffuses to fill the space available  Particles in rapid motion moving in straight lines until hitting an object and changing direction

 Melting-solid changing to liquid.  Particles are moving fast enough that attractive forces are no longer able to hold particles together  Freezing-liquid to solid  As heat is withdrawn from liquid, particles slow down enough that attractive forces can take hold  Evaporation-liquid becomes gas.  As heat is added, particles have more kinetic energy and move faster. Eventually have enough energy to jump out of the liquid into the air (become a gas).

 Boiling-Liquid becomes gas.  Rate of evaporation increases as temperature increases.  When temperature is hot enough, evaporation occurs beneath surface of liquid.  Bubbles form and rise to surface  Condensation-opposite of boiling

 Density is amount of mass divided by the volume of sample  Units in grams per milliliter or grams per cm 3  Densities of gases are more affected by pressure and temperature than solids and liquids