Chemistry terms (Term 3)

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Physical change

the ability to change between states of matter

these state changes (or phase changes) involve removing or adding heat in order to change

which also involves absorbing or releasing energy

Chemical change

when energy breaks apart the chemical bonds in a molecule,

involves ionic; covalent; and metallic bonds,

the product is atoms rearranged in a new way and not created nor destroyed

States of matter + labels

Solid (s)

Liquid (l)

Gas (g)

Aqueous (aq)

Single displacement reaction

A + BC —> B + AC

involves reactivity series

Double displacement reaction

AB + CD —> CB + AD

(C and A are positive)

(B and D are negative)

Acid-base reactions

Acid + Base —> Salt + H2O + CO2

(aq) + (aq) —> (aq) + (l) + (g)/ (aq) + (l)

VSEPR

(Valence Shell Electron Pair Repulsion)

Electron pairs will arrange themselves in ways to be as far away from each other as possible.

It explains why molecules are shaped the way they are

Lone pairs

2 unbonded electrons.

Involved in determining the shape

makes the paired and unpaired electrons repel each other

(same with bonded electrons)

Polarity

The movement of electrons in an electronegative reaction between molecules

Dispersion forces

when random, temporary dipoles are created as a result of electrons moving sporadically.

Larger molecule = more electrons = more polarisable = stronger.

Longer chains = stronger dispersion.

Branching = weaker dispersion

Dipole-dipole forces

Only occur in permanent, proper, polar bonds.

Stronger than dispersion forces but relatively weak.

Stronger dipole-dipole forces = higher melting/boiling point

Hydrogen bonding

hard form of dipole-dipole forces.

ONLY OCCUR when bonding to oxygen, nitrogen, or fluorine

Kinetic theory of gas

when kinetic theory explains the property of gases

--> small particles of gaseous atoms/molecules only occupy a small amount of space when contained,

intermolecular forces between gas particles are extremely weak = easily broken by molecule kinetic energy

= independent movements in rapid, random straight-line motions

colliding with other particles and the wall

Kinetic energy formula

KE = 1/2mv²

Pressure formula

Pressure = force/area

Units of pressure (in order)

1. kPa

2. Pa

3. atm

4. mmHg

Ideal gas law

Ideal gas = follows the rules perfectly in which it would have no volume if the temperature is low enough;

collisions are never truly elastic;

there are no intermolecular reactions, and energy is not lost in interaction.

Ideal gas equation

PV = nRT

P variable

pressure (in kPa)

V variable

Volume

n variable

moles

R variable

R = 8.31 JK-1

T variable

temperature = K (kelvin)

HAS TO BE CONVERTED TO KELVIN

Gas constant

The units of R depend on the units of temperature and pressure used

Viscosity

the description of how thick or thin a fluid is.

The thicker it is, the higher its viscosity.

The thinner it is, the lower its viscosity