Chapter 3: MatterProperties and Change

Solid: Particles are tightly packed and do not move.

Liquid: Particles are not rigidly held in place and are able to flow freely .

Gas: Particles are completely free to move. Plasma: Plasma is ionized gas.

States of matter

A physical property of matter is a characteristic that can be observed or measured without changing the sample’s composition.

Extensive Properties: Depend on the amount of the substance being studied.

Intensive Properties: Do not depend on the amount of the substance being studied.

Physical Properties of Matter

The ability of a substance to combine or change into one or more other substances is called a chemical property.

Chemical Properties of Matter

Physical changes: A change that alters a substance without changing its composition.

Example: Melting ice Chemical change: A process that changes

one substance in to another substance. Also called a chemical reaction.

Changes in Matter

The law of conservation of mass states that matter cannot be created or destroyed.

In other words the mass of the reactants in a chemical reaction must be equal to the mass of the products.

Conservation of Mass

A mixture is a combination of two or more pure substances.

A heterogeneous mixture is a mixture that does not blend smoothly throughout.

A homogeneous mixture is a mixture that does blend smoothly.

Homogeneous mixtures are also referred to as solutions.

Mixtures of Matter

Filtration: Used to separate solids from liquids in heterogeneous mixtures

Distillation: Used to separate two liquids based on their boiling points.

Crystallization: Used to separate a pure solid from a liquid in a homogeneous mixture

Chromatography: Used to separate two liquids based on their ability to “stick” to the surface of a specific material.

Separating Mixtures

An element is a pure substance that cannot be separated into simpler substances by physical or chemical means.

Example: Anything on the periodic table A compound is made up of two or more

different elements that are chemically combined.

Elements and Compounds

The periodic table

The most important thing about compounds is that the elements that make them always combine in the same proportions.

This is called The law of definite proportions.

Percent mass:

More about compounds

The same two elements can combine in different proportions to create different compounds.

Example: H2O and H2O2

Law of multiple proportions

The atom is the smallest individual unit of a given element.

All matter is composed of atoms. Atoms are composed of three subatomic

particles: Electrons Protons Neutrons

The atom

The electron

The nucleus of an atom is comprised of protons and neutrons.

Protons are subatomic particles that have a charge of +1 and a mass of 1 amu.

Neutrons are subatomic particles that do not have a charge and a mass of 1 amu.

Rutherford Experiment:

The Nucleus

An atoms atomic number is the number of protons that it has.

Neutral forms of atoms have the same number of electrons as protons.

Mass number: An atoms mass number is the sum of the

atoms protons and neutrons. Atoms with the same number of protons but

different number of neutrons are called isotopes.

How atoms differ

Before we talk more about electrons we need to talk about light.

Visible light is a type of electro magnetic radiation.

EM radiation is both a particle and a wave.

Electrons

Matter can only gain or lose energy in small, specific amounts called quanta.

A quantum is the minimum amount of energy that can be gained or lost by an atom.

Energy and atoms

When atoms gain enough energy they emit electrons at certain wave lengths and energy levels (quanta).

The equation to calculate the energy of a photon emitted is:

E = hv Where h is planks constant and v is

wavelength.

The Photoelectric effect

The atomic emission spectrum of an element is the set of wavelengths of the electromagnetic waves emitted by atoms.

Atomic emission spectrum

The lowest allowable energy state of an atom is called its ground state

Danish physicist Niels Bohr proposed that electrons in atoms can only have certain allowable energy states.

As electrons gain energy they are promoted to higher energy states.

Energy states of hydrogen

Principle energy levels:◦ Principle energy levels are the major energy

levels that electrons can occupy.◦ n = 1◦ n = 2◦ n = 3

◦ With in these principle levels there are sublevels◦ energy level one consists of one sublevel, energy

level 2 consists of 2 sublevels, energy level 3 consists of 3 sublevels and so on…

Quantum numbers and energy levels

Quantum theory and the atom

n = 1◦ s

n = 2◦ s◦ p

n = 3◦ s◦ p◦ d

n = 4◦ s◦ p◦ d◦ f

Principle energy levels

Low energy states are more stable that high every states.

Because of this atoms like to have their electrons in their ground states.

The aufbau principle states that each electron will occupy the lowest energy level available.

The pauli exclusion principle states that the maximum number of electrons that can occupy a single atomic orbital is two.

Hund’s rule states that single electrons with the same “Spin” must occupy each equal energy orbital before additional electrons can be added.

Ground State electron configurations

Start by figuring out how many electrons and atom has.

Set up an electron configuration table.

Place electrons in orbitals one at a time before going to back to fill an orbital.

Electron configuration

Write the ground-state electron configuration for the following elements.

Boron (B)

Strontium (Sr)

Antimony (Sb)

Rhenium (Re)