Key Terms for Chapter 4 ViscosityBoiling point Absolute zeroCompressibility KelvinAmorphous solid SublimationCrystalline solid CondensationBrownian movement Bose-Einstein condensateDiffusion EvaporationFreezing point Melting pointCondensation point 1

Chapter 4 PROPERTIES OF MATTER 2

Properties of Matter  Physical Properties  A characteristic of the object/material (color, shape….)  Physical Changes  A change in a material that does not alter its identity  Chemical Properties  Describes how matter will react in the presence of other matter  Chemical Changes  Alters the identity of the material (iron rusting, burning wood) 3

Physical Properties  Property that can be observed and measured without a change in the kind of matter being observed  Examples  Color  Density  Shape  Texture  Hardness  State or Phase  Conductivity 4

Physical Changes  Does not alter the identity of the material  It is a change in a physical property  It remains the same kind of matter  Generally easy to reverse  Atoms do not rearrange  Ex.: cutting a piece of paper, freezing water… 5

Chemical Properties  Describes how matter will react in the presence of other substances  Ex. The tendency of iron to rust 6

Chemical Change  Alters the identity of the material and forms a new kind of matter  Generally called a chemical reaction  Both physical and chemical properties change  Atoms are rearranged: new chemical formula  Generally not a reversible reaction  Energy is often produced or absorbed  Ex.: burning, rusting 7

Physical or Chemical change?  Water evaporates into steam  A piece of cork is cut in half  A bicycle chain rusts  A piece of apple rots on the ground 8

Models  Ideas that represent what might be happening  No model is perfect  Models can change  Good models  Organize ideas  Describe observations  Help us describe what we cannot see  Predict what will happen  Different types of models  Solar system models  DNA 9

Matter  Aristotle (and other Greek philosophers) believed that matter was continuous  It could be divided infinitely without changing it  This concept was generally accepted from about 500 B.C. for 1500 A.D 10

Particle Model of Matter  Matter could only be subdivided to a certain point – eventually you would not be able to divide it any more  Ex. Water droplet  Measure those particles in angstroms and nanometers  These particles are called atoms  Two or more atoms joined together forms a molecule 11

Particle Model  You can watch the diffusion of food coloring in water whether you stir it or let it sit  If you let it sit long enough, the solution will spread throughout the water without stirring. How?  Brownian Movement: describes the constant motion of particles in a liquid or gas  1 st introduced by a botanist Robert Brown  Diffusion: mixing by this particle motion 12

Phases of Matter  4 phases of matter  Solid  Liquid  Gas  Plasma 13

Solid  Definite shape  Definite volume  Usually dense: particles are packed closely together  Low compressibility  Particles vibrating in fixed position  Low kinetic energy: strong attractive force 14

Solid  Occur in 2 basic forms:  Crystalline: atoms are in a fixed, repeating structure in solid  Amorphous: atom arrangement is random  Ex. glass 15

Liquid  Definite volume  No definite shape  Low compressibility  Random particle movement: Brownian Motion  Particles fairly close  Fairly equal kinetic energy to attractive force  Viscosity: the ease with which a liquid will flow  Low viscosity: liquid flows very easily (water)  High viscosity: liquid does not flow easily (pancake syrup) 16

Gas  Indefinite shape  Indefinite volume  High compressibility  Particles are far apart  More kinetic energy than attractive force  Brownian motion  Gas pressure: from the collisions of the gas particles with the sides of the container (ex. Balloon)  Heat gas = more kinetic energy 17

Comparing Phases SolidLiquidGas VolumeDefinite Indefinite ShapeDefiniteIndefinite CompressibilityLow High 18

Bose-Einstein Condensate  Hypothetical phase of matter that exists at absolute zero  Particles of the object behave as a single atom  Still being studied in labs to determine it’s uses 19

Phase Changes of Matter  Temperature increases = energy increases  Temperature decreases = energy decreases  Adding and removing energy will result in a phase change  The type of matter stays the same 20

Phase Changes  Phase changes that add energy  Melting  Vaporization  Boiling  Evaporation  Sublimation 21

Melting  Change from a solid to a liquid  The temperature at which melting occurs is called the melting point Water: 0 o C or 32 o F 22

Vaporization  Change from liquid to gas  Boiling  Occurs very quickly  Depends on the air pressure above  Boiling point: temperature at which substance boils  Evaporation  Occurs very slowly 23

Sublimation  Change from solid to gas (without becoming a liquid)  Solid particles gain enough energy to escape into the atmosphere Ex. Dry ice, moth balls, snow 24

Phase Changes  Phase changes that remove energy  Freezing  Condensing  Deposition 25

Freezing  Change from liquid to solid  Liquid particles lose enough kinetic energy that the attractive forces hold the particles in place  Temperature at which this occurs is freezing point Water: 0 o C or 32 o F 26

Condensing  Change from gas to liquid  Temperature at which this occurs is dew point (condensation point) Ex. Dew 27

Deposition  Change from gas to solid (without becoming liquid) Ex. Frost, Ice on wings of plane 28

Measuring Energy  Temperature:  Measure of average Kinetic energy  Different than heat (total Kinetic energy)  Celsius: 0 C  Fahrenheit: 0 F  Kelvin: K  Absolute zero: the temperature at which all molecular motion would cease 29

Conversions  C to K – add 273  K to C – subtract 273  C to F – (C x 1.8) + 32  F to C – (F – 32)/1.8  MEMORIZE THESE CONVERSIONS 30

Conversions  Convert -182 o C to K = 91 K  Convert 298 K to o C 298 – 273 = 25 o C  Convert 68 o F to o C = 36/1.8 = 20 o C  Convert 312 K to o F 312 – 273 = 39 o C (39 x 1.8) +32 = o F 31