Chapter 2 notes  Konichek

 I. Chemistry-The study of matter and the changes it undergoes  A.Pure substance or mixture-Matter with a fixed composition and definite properties  1. elements, and compounds  2. separated using chemical processes

 I. Chemistry-The study of matter and the changes it undergoes  A. matter- has mass and occupies space  1. element- a substance which cannot be broken down any farther by ordinary chemical changes-115 elements- could be more  1. element- a substance which cannot be broken down any farther by ordinary chemical changes-115 elements- could be more  a. Atom- This is the smallest piece of an element  1) 115 or so different types of atoms  2. element designation  a. one or two letters which are the same world wide 

 B. compound- two or more elements which are chemically combined  1. Have different physical properties than the elements which make them up  a. rust- iron(III) oxide, water  2. Molecule- The smallest unit of a substance that exhibits all the properties characteristics of that substance( Book definition)  a. teacher definition- Two or more elements which are covalently bonded  b. Molecules act as a unit.

 C. Chemical formula-Tells the number of elements and atoms in the compound, and the ratio which they combine.  1. subscript- Tells the number of atoms in the compound  2. coefficients- tells the number of molecules  H 2 + O 2 -  2H 2 O produces 2 molecules of water

–D.Formula mass- this is the sum of the atomic mass of the elements in the compound  E.To find the atomic mass have to look on the periodic table….Oxygen round it off to 16.  1.O 2= 16 x2= 32  2.H 2 O= 2(1)+ 16= 18  3.Be(C 2 H 5 O 2 )

 B. Mixture- Two or more substance which are put together which are not chemically combined  1. separated using physical means  2. Types of mixtures  a. heterogeneous-The parts are easily identified  b. Homogeneous- The parts are not easily identified, looks the same throughout  c. Liquid mixtures  1. miscible- The parts of the mixture don’t separate, and it looks the same throughout  2. immiscible- Two or more liquids which do not mix with each other.   d. mixing gases with liquids- gases can be dissolved in liquids under pressure.

 III. MATTER AND ENERGY( 2.2)  A. Kinetic theory- An explanation of the behavior of matter  1. All matter is made of atoms and molecules which act as tiny particles  2. the particles are in constant motion which depends upon the average Ke (temperature)of the substance  a. The particles are constantly colliding without losing energy( perfect elastic collisions)  3. At the same temperature more massive particles move slower and the less massive move faster  B. KMT - helps understanding the differences in the 3 common states of matter

 C, STATES OF MATTER- Depends on the distance and the angles between molecules or atoms  1. gases- High energy content  a. no definite shape or volume  b. Take the shape of the container

 2. Helium filled balloons lose air faster than air filled balloon- because the small He atom can go through the membrane of the balloon easier.  3. pressure- the gases colliding with the sides of the container, as more atoms go inside the balloon the more collisions occur... eventually the balloon will burst

 2. Liquids- Have a definite volume, but no definite shape  a. The atoms are able to move about each other freely  1. fluids- all liquids and gases  b. Viscosity-A fluids ability to flow  1. Depends upon an attraction between particles in the liquid

 3. Solids- Have definite shape and volume  a. The atoms are in a definite arrangement, this provides the shape  b. relatively low energy content.  c. Strong attraction between atoms or molecules 

 D ENERGIES ROLE  1. MELTING- THE PROCESS OF CHANGING A SOLID TO A LIQUID  a. The particles are changing their positions and gaining energy, so they will not want to remain in their set positions.  2. Evaporating- The particles have gained enough energy to escape from the liquid form to the gaseous form

 3. CONDENSATION- The process of changing from a gas to a liquid- losing heat.  4. Sublimation- When a substance goes from a solid directly into a gas  a, dry ice, iodine  5. During a change in state composition remains constant and no mass is lost  E. Conservation of mass- Mass cannot be created or destroyed.  1. Must end up with the same amount of matter which is started with

 F. conservation of energy- Energy cannot be created or destroyed- First Law of Thermaldynamics  a. The total amount of energy during a chemical reaction remains constant  1. Burning of gasoline in a car engine

 IV. PROPERTIES OF MATTER  A. Chemical and physical properties  1. Chemical property- the way a substance reacts with other substances to form new substances with different physical properties.  1. H 2 + O > H 2 O  2. Reactivity- The ability of a substance to combine chemically with other substances.  a. depends upon their position on the periodic table.

 2. physical property-a characteristic of a substance which can be observed or measured without changing the composition of the substance.  a, color, size, shape, state, density. melting point, boiling point.  b. density- mass per unit volume- characteristic property  1. D= mass/ volume d=m/v  2, buoyancy- The force with which more dense fluid pushes a less dense substance upward.

 V. CHEMICAL AND PHYSICAL CHANGES  A. Chemical changes- A change that occurs when a substance changes composition by forming one or more new substances.  1. Have different physical properties  2. electrolysis of water.  3. burning of gasoline- Changes the composition  B. physical changes- the composition doesn’t change.

Physical change- a change in state

Chemical change- rusting of a nail

 1. The atoms which make up don’t change or are rearranged  2. A change in size, shape, or state.  3. Dissolving is a physical change- sugar in water

SUMMERIZING  1.Definition Physical ChangeThe matter is the same. 2.The original matter can be recovered.The particles of the substance are rearranged.  3.Chemical ChangeThe matter is different. The old matter is no longer present.  4.The original matter cannot be recovered.  5.The particles of the substance are broken apart, and the atoms are rearranged into new particles, forming a new substance.