Matter Chapter 2

Chemistry  The study of matter and how it changes  Matter = has mass and takes up space  Simplest form of matter = Atoms  Different types of atoms = elements. (they cannot be broken down)

Compounds  Atoms of more than one element bound together.  Ex: H 2 O, C 6 H 12 O 6, NaCl, HCl  Molecule = smallest unit that exhibits all the properties of that substance  Ex: H 2 O, C 6 H 12 O 6

Chemical Formulas  Chem symbols and numbers tell us how many of each element is in a compound  Example: The chem formula for table sugar is C 12 H 22 O 11. Each molecule contains 12 carbon atoms, 22 hydrogen atoms, and 11 oxygen atoms.

Types of Matter  Pure Substance = matter with fixed composition and definite properties  Mixture = Combination of more than one pure substance.  Ex: Grape Juice is a mixture of pure substances such as water, sugar, vitamins, etc…

Types of Pure Substances  Elements – listed on the Periodic Table  Compounds – Combination of elements

Types of Mixtures  Heterogeneous – subs are NOT uniformly mixed  Example: mixture of flour and water  Homogeneous – subs are evenly mixed (looks the same throughout)  AKA Solution  Example: mixture of salt and water – the salt dissolves in the water

Liquid Mixtures  Miscible – liquids are able to dissolve into each other  Homogeneous mixture of liquids  Gasoline = homo. mixture of 100 compounds  Immiscible – liquids are NOT able to dissolve into one another  Heterogeneous mixture of liquids  Oil and water will not mix

Buoyancy  The force with which a more dense fluid pushes a less dense subs up.  Ice is less dense than water.

Archimedes’ Principle 4the buoyant force on an object equals the weight of the fluid displaced by the object

Bernoulli’s Principle 4As the velocity of a fluid increases, the pressure exerted by the fluid decreases 4Explains why planes can fly

Mixtures with Gases  Many gases form mixtures with other gases or liquids  Ex: Air – homo. mixture of gases  Ex: Soda – homo. mixture of gas and liquid  Ex: Foam – mixture of gas and liquid

Kinetic Theory  All matter is made up of atoms or molecules.  The atoms/molecules are always in motion.  More massive atoms/molecules move slower.

States of Matter  Solid  Liquid  Gas  Plasma – most common state in the universe  Very fast moving charged particles  Makes up stars

Solids  Definite volume and shape – “Rigid”  Atoms are held together with strong forces  Particles vibrate in fixed position

Liquids  Definite volume, indefinite shape  Atoms slide past one another  Viscosity = property that describes the resistance of a fluid to flow

Gases  Indefinite shape and volume  Atoms not very attracted to each other  Free motion  Exert pressure

Energy  Ability to cause changes in the states of matter (phase changes)  Evaporation  Liquid  Gas  Energy is absorbed (by a liquid causing atoms to move faster until they break away from the liquid surface to form a gas.)

More Phase Changes  Condensation  Gas  Liquid  Releases energy (energy is given from the gas to the surroundings)  Sublimation  Solid  Gas  Energy is absorbed  Ex: CO 2 (s)  CO 2 (g) Dry Ice

 Insert picture from p. 382 chemistry book

Phase Change Diagrams  Show the changes of state for any subs.  Show the temperatures where the phase change occurs  Is more energy used to convert ice to water or water to steam?

 Insert phase diagram on p. 49

Heat of Fusion  Amount of heat required to melt a solid at its melting point  Different for every subs.

Heat of Vaporization  Amount of heat needed to change a liquid into a gas at its boiling point  Also different for every subs.

State Changes  No change in the composition or mass of the atoms.  Law of Conservation of Energy  Energy cannot be created or destroyed  Law of Conservation of Mass  Mass cannot be created or destroyed

Properties of Gases  Thermal Expansion = gas molecules become farther apart as temp increases  Pressure = Force exerted per unit area of a surface  Unit: atmospheres (atm)  Pressure around us comes from air molecules

Boyle’s Law  Relates pressure (P) and volume (V)  As P increases, V decreases  P 1 V 1 = P 2 V 2  Inverse relationship

Charles’s Law  Relates V and temperature (T)  As T increases, V increases  V 1 = V 2 T 1 T 2  Direct relationship

Combined Gas Law  Includes P, V, and T  P 1 V 1 = P 2 V 2 T 1 T 2

Chemical Properties  Methods that a subs can use to transform into a new subs with different properties  Reactivity = ability of one subs to combine with another subs  Ex: flammability, corrosiveness, rusting, explosiveness,

Physical Properties  Characteristic of a subs that can be observed without changing the subs  Ex: Melting point (s  l) Boiling point (l  g)

Density  Physical property  The amount of mass in a certain volume  D = m/V  Units = g/mL or g/cm 3

Chemical Changes  Change that occurs to form a new subs. (product has a different composition.)  Ex: Digesting food, steel rusting, food burning, gasoline combusting, milk souring

Signs a Chemical Change Occurred  Odor  Color change  Gas produced (bubbles)  Solid produced  Temperature change (hot or cold)

Physical Changes  Change that does NOT alter the composition of the subs.  Melting chocolate, freezing water, tearing paper, chopping food, dissolving sugar  Dissolving = water molecules surround the other molecules and spread them out evenly.