Chemistry - Physical Properties of Matter

properties (or characteristics) describe:

1. what can be observed by examining the substance

2. the way it behaves when brought into contact with other substances or exposed to sources of energy

extensive

those that depend on the amount of substance you have (eg. volume, weight, and mass)

intensive

those that do no depend on the side of the sample (eg. melting point)

Physical properties

characteristics that can be observed without the production of new substances

ex.: colour, odor, taste, density, melting and boiling points, electrical conductivity

physical properties of metals ex

malleable - capable of being changed, molded, shaped

ductile - stretched, hammered without breaking (wires)

luster - gloss, sheen

conductivity - ability to carry a current

physical change

involves the change of one or more physical properties=, but there is not change in the substances’s chemical composition or properties.

No new substances produced

eg.: Ice, water and steam have the same composition (88% O2, 11.2% H2)

ex.: changing physical appearance (crushing, blending), phase changes (solid, liquid, gas (boiling water, meting etc)), colour change, grinding a substance

chemical properties

characteristics that describe how the substance interacts (or fails to) with other substances to produce new substances

ex. iron rusting, failure of nitrogen gas to react chemically, flammability, toxicity, heat of combustion, chemical stability

chemical changes

any change that result int the production of one or more substances that differ in chemical properties and composition from the original substances

ex. souring of milk, burning of paper

changes in energy

includes absorption or energy and release of energy

every change, whether physical or chemical, involves an energy change

change in energy for physical changes tends to be less noticeable than those accompanying chemical changes

absorption of energy

a reaction that absorbs or used energy is said to be endothermic

(think endo → taking in the heat inwards)

physical - melting of ice, evaporation of water

chemical - formation of hydrogen gas and oxygen gas from water

release of energy

a reaction that releases energy is said to be exothermic

(think exo → heat being released → exo, outside)

physical - freezing of water, crystallization of a solid

chemical - burning wood

density

the mass of one unit volume of a substance

All substances have a specific, unique density

physical property of matter

density = mass/volume

grams per litre

can help us determine whether something will sink or float

compressibility

the ability of particles to move closer together

diffusion

movement of one substance through another

4 states of matter

solid

liquid

gas

plasma

solid

has a definite shape and volume

shape doesn’t depend on container

particles are tightly packed together, often in an ordered arrangement

will expand slightly when heated

usually incompressible

varying density ex. iron 7.87g/cm3, gold 19.3g/cm3, calcium 1.54g/cm3

liquid

particles of a liquid are in close contact, but arrangement is not rigid or orderly

flow freely, liquids take the shape of the container (some liquids pour easier than others)

volume remains constant, even if shape changes

almost/usually incompressible

will expand slightly when heated

can diffuse easily from areas of high concentrations to low concentrations

varying densities ex. mercury 13.53g/mL, water 1g/mL

gases

flows freely, will take the shape of the container

will expand to fit any volume

particles in a gas are much farther apart than solids and liquids

easily compressed

can diffuse easily from areas of high concentrations to low concentrations (ex. orange particles are easily diffused throughout the class room)

varying densities ex. hydrogen 0.089g/cm3, oxygen 1.43g/cm3, chlorine 3.21g/cm3

Plasma

a gaseous of mixture of positive ions and electrons

formed at higher temperatures greater than 100 million celsius when electrons are stripped from neutral atoms

very unstable

most common form of matter in the universe, comprising 99% of the visible universe, but are the least common on earth

DO NOT occur naturally on Earth except in the form of lightning bolts

ex. aurora borealis, lightening, florescent lights, and stars

neon sign - glass tubes filled with gas, electricity is turned on and charges the gas, creating plasma insides the tube and the colour depends on type of gas

kinetic

motion, comes from the greek word kinetos, ‘to move”

kinetic energy

"the energy an object has because of its motion

the main assumptions of the Kinetic Theory

i. the particles in a gas are considered to be small, hard spheres with an insignificant volume. (All particles are made of matter)

ii. the motion of the particles in gas is rapid, constant, and random. (Particles are in constant motion. The amount of motion depends greatly on the kinetic energy of a substance)

iii. all collisions between particles in a gas are perfectly elastic. (No change in kinetic energy takes place and particles bounce off each other without losing kinetic energy, only changing direction)

what is an ideal gas

a hypothetical gas composed of molecules that don’t attract nor repel each other

one that follows the gas laws at all conditions of pressure and temperature. Such a gas would have to conform precisely to the assumptions of kinetic theory

explain how “average kinetic energy” of a collection of particles is related to temperature

the particles in any collection of atoms or molecules at a given temperature have a wide range of kinetic energies

the average kinetic energy is used when discussing the kinetic energy of a collection of particles in a substance.

at any given temperature the particles of all substances have the same average kinetic energy

as the average kinetic energy increases, the temperature of a substance will rise

why is Kelvin temperature used when discussing the kinetic energy of a sample? What is the relationship between Kelvin and degrees Celsius?

the kelvin temperature is directly proportional to the average kinetic energy of the particles of a substance.

ex. helium at 200K has twice the average kinetic energy of helium at 100K

kelvin temperature

directly proportional to the average kinetic energy of the particles in a substance

K = C + 273.15

explain how the kinetic theory applies to liquids

liquids have kinetic energy, which means that they are always in motion

explain how the kinetic theory applies to solids

solids are made of matter, and their particles are in constant motion (they vibrate), which means that they also have kinetic energy

kinetic energy

energy due to motion of an object

potential energy

stored portion of energy

average kinetic energy

used when talking about the kinetic energy of a substance

temperature

a measure of the average kinetic energy of the particles of a substance

absolute zero

-273C or 0 Kelvin

there is a temperature at which all particles of a substance will stop moving

crystal structure

most solid substances are crystalline (clear, transparent, or sparkling like crystal, or made of crystals, or having the regular structure of a crystal)

in a crystal, particles are arranged into an orderly, repeating 3 dimensional pattern called a lattice

shape of a crystal reflects the pattern of the particles within the solid

there are 7 crystal systems that can be distinguished by the angle at which the faces of the crystal intersect

the 7 crystal systems that can be distinguished by the angle at which the faces of the crystal intersect

isometric

hexagonal

tetragonal

trigonal

orthorhombic

monoclinic

triclinic

unit cell

the smallest group of particles within a crystal that retains the geometric shape of the crystal is known as the unit cell

the unit cell in a cubic crystal system may be simple cubic, face-centered cubic, or body-centered cubic

allotropes

2 or more molecular forms of the same element

ex. carbon

diamond - each carbon atom i bound to 4 others in tetrahedrons making it extremely rigid

graphite - sheets of linked hexagons, like chicken wire. stacked sheets have weak bonds holding them together making them slide easily and therefor soft and greasy

fullerenes - 60 carbon soccer ball shape, no known use yet. “buckmisterfullerene” 1996 Nobel Prize in Chemistry

allotropes of an element have different properties bc of their arrangement of the atom. Only a few elements have allotropes: carbon, phosphorous, sulfur, oxygen, boron, and antimony

amorphous solids

lacks an ordered arrangement of atoms (ex. glass)

atoms are randomly arranged

ex. rubber, plastic, peanut butter, and asphalt