chem midterm

Accuracy

How close data is to accepted value

Precision

How close data points are to each other

System

Specific portion / region of matter

Volume

Amount of space particles take up

Mass

Amount of particles in a system

LoCM

Particles entering / exiting the system

Density

1. Amount of particles in a given space

2. Amount of space b/w particles

3. Relationship b/w mass and volume

Sink

Objects with more density pushes less dense particles out of the way

Float

Objects with lower density don’t have enough space between particles to push through the higher density particles

Density differences

Determine how they arrange themselves (p. Diagrams)

Solid

Tightly compact, fixed shape

Liquid

Close t/g particles, easily moveable

Gas

Wide-spread, free moving particles

Endothermic

Energy enters system

Exothermic

Energy exits the system

How do energy changes happen

Happens through collisions. When particles collide more often and with greater force, they transfer energy to each other, increasing their kinetic energy and causing faster motion or phase changes

Heat

Total energy (Ek + Eph)

Temperature

The average Ek of particles

Potential energy

Energy of position , space b/w particles (Eph)

Variables that affect heat

Mass, temperature, specific heat capacity

Specific heat capacity

energy required to increase 1g by 1 degree ( j / gCdegree)

LoCE

energy that exists has to equal the amount that enters

Are particles in constant motion

All matter is made up of particles that move continuously and randomly

variables that affect kinetic energy

1. increased motion with temp increase

2. decreased motion with mass increase

speed of particles in temp and mass terms

1. when temperature increases, particles move faster

2. lighter particles move faster than heavier ones at same temp

variables that affect gas behavior

1. pressure

2. temperature

3. volume

4. number

pressure

number of particle collisions with the system

number

number of particles exiting / entering the system

what is the relationship between each variable

positive: (T,P)(T,V)(n,V)(n,P)

negative: (V,P)(T,n)

particle level explanation for variables impacting gas behavior

if the temp of a gas increases, pressure will also increase because when gas particles are heated, they move faster and collide with the system walls more often and with greater force.

Avogrado’s Law

adding more particles to a system at a constant temp and pressure amount increases volume, so particles spread out filling the space, maintaining the same pressure

Evaporation vs. Boiling

Evaporation: surface of liquid, a few higher particles escape, can happen below boiling point

Boiling: throughout the liquid, particles inside liquid gain enough energy to form bubbles and leave system, occurs when vapor particles = atmosphere particles

explain size of atoms

atoms are smaller than visible light waves

Democritus

greek philosopher, first to suggest atoms; atomos = indivisible

Dalton

1. all elements can be broken into atoms

2. atoms are the smallest part of element to be considered

3. same element = identical atoms

4. atoms CANT be created, destroyed, divided

Thompson

discovered electron; cathode ray tube and plum pudding model

Rutherford

search for proton (never found), gold foil experiment

Chadwick

discovered the neutron; alpha particles, beryllium and wax

cathode ray tube

conclusion: subatomic particles making up the beam must be negatively charged and very small (calculated by deflections)

evidence: when a magnetic field was brought near the cathode ray tube, the beam was deflected

Gold Foil Experiment

1. Atom is mostly empty space

2. Nucleus is small and dense

3. Nucleus is positively charged

proton

+1 charge, 1amu, nucleus

neutron

0 charge, 1amu, nucleus

electron

-1 charge, 0amu, orbitals

Schrödinger model

probability equations to predict probable loco of an electron within a region

orbitals

regions of space where there is a high probability of finding an electron