Chemistry: Unit 2 Matter and Change

matter

anything that has mass and takes up space

chemical

everything made of matter

if it does not contain matter…

it is not a chemical (heat, energy, thoughts, gravity, force)

most important chemical compound

water

4 fundamental forces

1. gravity

2. electrostatic force

3. strong nuclear force

4. weak nuclear force

what can models show?

atoms, ions, molecules, and chemical bonds up close

ball and stick models

show atoms joined together

space filling models

show the overall molecular shape but not bonds

any sample of matter is either

a pure substance or a mixture

pure substance

every piece of matter is the same

mixture

more than one substance or state of matter mixed together, homogeneous or heterogeneous, can be any combonatioin of solids, liquids, or gases.

pure substances are either

elements or compounds

element

every particle is the same type of atom, cannot be separated, on periodic table

compound

every particle is the same combination of elements, expressed by a chemical formula, separation requires a chemical reaction

water

H2O

table salt

NaCl

methane

CH4

amonia

NH3

homogeneous

(solution) looks the same throughout

heterogeneous

different matter can be seen (chunks, bubbles, layers)

mixtures can be separated by

taking advantage of the unique physical properties of the substances in the mixture

distillation

a physical process that separates the parts of a liquid mixture by heating it to create vapor and then cooling that vapor back into a liquid

filtration

a physical method used to separate solid particles from a liquid or gas by passing the mixture through a filter

magnetism

used to separate substances that have different magnetic properties, magnetic can be pulled away

chromatography

can separate solutions, a solvent carries the ink over paper or a silica plate. the ink causes them to travel different distances over the solid phase

liquid particles

• close together, not compressible

• higher KE and able to break free of some IMFs between them

• are able to move past each other and flow

• definite volume, indefine shape

gas particles

• very spread out

• rapid, random motions- high KE

• highly compressible

• no definite volume

• no definite shape ( would fill container and take shape)

what’s between gas particles?

nothing

solid particles

• closely packed together

• vibrate in place, low KE

• cannot switch places

• not compressible

• definite volume and shape

solid to gas

sublimation

solid to liquid

melting

liquid to gas

vaporization, evaporation, boiling

liquid to solid

freezing

gas to solid

deposition

gas to liquid

condensation

as temp goes uo

kinetic energy goes up

slope on heat and cool curve

temperature is changing

plateau on heat and cool curve

temperature is not changing but undergoing a change of state, energy is now being used to overcome imfs

first plateau

freezing/melting

second plateau

condensing, boiling, etc.

third slope

gas or vapor is warming

physical properties

characteristics that can be measured or observed without changing the identity of the substance

ex. density, mass, shape, color

chemical properties

characteristics having to do with how the atoms and molecules can be combined with or rearranged into other substances": change in the identity of a substance

ex. reactivity, flammability

physical change

a change that alters the substances physical properties but does not change the molecular structure

chemical change

a change that alters the substance arrangement of atoms changing the chemical properties and identity

physical changes do not result in new substances

chemical changes do

physical properties ex

malleable, ductile, sublimes, luster, viscosity, solubility

chemical properties ex

flammable, combustible, corrosive, oxidizer, reducing agent

physical change ex

change of state, dissolving

chemical change ex

cooking, metabolizing, decaying, spoiling, souring, growth of living organisms, oxidizing, rusting, tarnishing, combusting, neutralizing

when a material changes phase, substance is the same,

speed of atoms is different

basic signs of chemical change

change in color, temperature, smell, precipitate, gas

precipitate

two solutions making a solid

4 properties of gas

1. pressure

2. number of particles

3. volume

4. temperature

pressure

the force of gas particles hitting a surface

pressure & number of particles

• directly related

• as n increases, p increases

• as n decreases, p decreases

pressure & volume

• inversely related

• as v increases, p decreases

• as v decreases, p increases

temperature

is proportional to the average KE of the particles

determined by mass and speed of particles

pressure & temperature

• directly related

• as t increases, p increases

• as t decreases, p decreases

atmospheric pressure

the pressure exerted by air due to successive layers of air in the atmosphere

atmospheric pressure decreases when

altitude increases

STP

standard temp and pressure, 1,000 atm and 0.00 C

pressure in a flexible container

pressure inside is higher, pressure outside is lower, container will expand to reduce pressure inside until equal

pressure in rigid containers

expansion isn’t possible, internal pressure becomes greater so it explodes

Kinetic Molecular Theory

an explanation of gas behavior based on the motion of molecules of an ideal gas (one that perfectly fits kmt conditions)

gases behave more ideal when

at higher temp and lower pressure

what has behaves closest to an ideal one

helium

1st assumption of KMT

gases are made up of a very large number of particles

2nd assumption of KMT

gases are in constant, rapid, random motion at constant speed

3rd assumption of KMT

the temp of a gas is proportional to the average KE of particles

4th assumption of KMT

gas particles are not reacting or experiencing any attractive or repelling forces with one another

5th assumption of KMT

gas particle collisions are perfectly elastic, no KE is lost or transformed to other energy

6th assumption of KMT

gas particle size is very small compared to the distance between them therefore the volume of the particle itself can be ignored with respect to the volume do the sample gas

real gas

a gas that is not beginning ideally or according to kmt, all gases.

real gas can occur

with any gas especially at low temp high pressure

real gases will experience

attraction and repelling towards one another

larger gas particles

effusion

gas escapes from a tiny hole in the container

diffusion

gas moves across the space

larger gas particles

take longer to get to your nose

how does particle mass affect effusion and diffusion rates?

as particle size/mass increases particles move slower, it takes longer to move, so effusion and diffusion rates are slower