Gr 11 Physics June Chemistry Exams

Front 1

How are ionic bonds formed?

Back 1

Ionic bonds are formed when electrons are transferred between atoms to make positive and negative ions

Front 2

How are covalent bonds formed?

Back 2

Covalent bonds form when atoms share pairs of electrons.

The bonded atoms form molecules.

Intermolecular forces hold the molecules into solids or liquids

Front 3

Define Electronegativity

Back 3

-This is the number assigned to an element and indicates the extent to which the atom will attract the shared pair of electrons in a covalent bond.

Front 4

How are Dative Covalent bonds formed?

Back 4

A dative covalent bond is formed by the overlapping of a filled orbital containing a lone pair with the empty orbital of another atom or ion.

Front 5

Discuss the shapes of molecules

Back 5

- The shape of a molecule depends on the number of electron pairs surrounding the central atom.

- The shape of the molecule can be predicted by using the VSEPR

- Electron pairs spread out equally in space

- Lone pairs take up more space.

Front 6

What does the acronym VSEPR stand for and what does it do?

Back 6

Valence Shell Electron Pair Repulsion theory

- it predicts that there is repulsion between pairs of electrons.

lone pair-lone pair > Shared pair-Lone pair > Share pair-Shared pair

Front 7

Name the different shapes of molecules and give an example of each.

Back 7

- Linear (BeCl2 / CO2)

- Trigonal planar (BF3)

- tetrahedral (CH4)

- pyramidal (NH3)

- bent / angular (H2O)

Front 8

Define bond energy and what do they indicate?

Back 8

The amount of energy needed to break the bond

- Bond energies give an indication of the stability of the bond because the larger the bond energy the harder it is to break the bond.

Front 9

Define bond length

Back 9

It is the distance between the nuclei of two covalently bonded atoms.

Front 10

Give a definition for intermolecular forces.

Back 10

- Intermolecular forces are the attractive forces between molecules or between molecules and ions.

- The forces between molecules determine whether a substance will be a solid, liquid or gas.

Front 11

Give a definition for Solids

Back 11

Solids have definite shape, volume and high density.

They are compressible and melt to form liquids.

Front 12

Define the term Liquids

Back 12

Liquids have definite volume but no definite shape.

- they are less dense and only slightly compressible

- they boil to form gases.

Front 13

What are gases?

Back 13

Gases have no definite volume or shape and low density

- they are very compressible

- the state of gas depends on its pressure & temperature.

Front 14

What does the Kinetic-Molecular Theory state?

Back 14

Kinetic-molecular theory states that all matter is made up of small particles (molecules) which are continually moving (kinetic energy).

Front 15

How does the kinetic molecular theory apply to solids?

Back 15

- The particles are fixed in position with little space between them, i.e. solids are dense.

- Forces hold the particles in place but they can vibrate. This vibration increases on heating and solids expand.

- At the melting point the particles vibrate to the point of breaking and form a liquid.

Front 16

How does the kinetic molecular theory apply to Liquids?

Back 16

- there are larger spaces between particles, less density.

- on heating particles move faster and further apart, i.e. expanding the liquid.

- When the liquid boils, the particles have enough energy and form a gas.

Front 17

How does the kinetic molecular theory apply to gases?

Back 17

- the forces are not strong enough to hold the particles together, they spread out and fill the container.

- on heating, the particles move faster and hit the sides of the container i.e. pressure increases.

Front 18

How are intermolecular forces classified?

Back 18

- particles may be positive and negative ions which originate in ionic compounds.

- particles may be polar molecules (dipoles) .

Front 19

Name and discuss the different van der Waals forces(6)

Back 19

A) Dipole-Dipole: attraction between the + end of the polar molecule and the - end of another. (HCl)

B) Dipole-Induced dipole: A polar molecule will cause the electron cloud of a non-polar molecule to become displaced. There will be an attractive force between the permanent dipole and the induced dipole.

C) Induced dipole - induced dipole: These are weak forces but they increase in strength with increasing size of the molecule.The charges on the induced dipole are larger and the forces between induced diploes are stronger.

Front 20

Give another name for Induced dipole forces

Back 20

London / Dispersive forces

Front 21

Define Hydrogen bonds

Back 21

When hydrogen combines with certain elements with high electronegativities it forms dipoles with greater / stronger polarity than the dipoles in Van der Waals forces.

Front 22

Name 5 different Intramolecular bonds

Back 22

- Covalent

- Polar covalent

- dative covalent

- Ionic

- Metallic

Front 23

Name types of intermolecular forces

Back 23

- ion-dipole forces

- ion-induced dipole forces

- van der Waals forces

Front 24

Name the 3 categories of Van der Waals forces

Back 24

A) dipole-Dipole forces

B) Dipole-induced dipole forces

C) induced dipole-induced dipole forces

Front 25

When does an induced dipole occur?

Back 25

It occurs when a nearby charged particle causes the attraction or repulsion of electrons in a nearby neutral molecule to form an induced dipole.

Front 26

What is a hydrogen bond?

Back 26

Forces between molecules in which hydrogen is covalently bonded to nitrogen, oxygen or fluorine.

Hydrogen bonds are special dipole-dipole forces.

Front 27

Define the term Volatility

Back 27

Volatility is a measure of the ability of a substance to evaporate

Front 28

What is the boiling point?

Back 28

The boiling point is the temperature at which the vapour pressure of a substance equals atmospheric pressure.

Front 29

Discuss the term surface tension

Back 29

Surface tension is the energy required to increase the surface area occupied by the liquid at its surface.

Front 30

What does solubility mean?

Back 30

Solubility is the measure of the ability of the solvent to break the bonds between the molecules in the solute and thus dissolve the solute.

Front 31

What is Capillarity?

Back 31

Capillarity is the tendency for liquids to spontaneously rise or fall in narrow tubes.

Front 32

Define viscosity

Back 32

Viscosity is a measure of the resistance of a liquid to flow.

Front 33

Define density.

Back 33

Density is the mass per unit volume of a substance.

Front 34

Explain thermal expansion

Back 34

Thermal expansion is a measure of the increased in volume of a substance as its temperature is increased.

Front 35

What is thermal conductivity

Back 35

Thermal conductivity is the measure of the ability of a substance to conduct heat.

Front 36

What is a solvent?

Back 36

A solvent is a substance (often a liquid) that dissolves under substance, called the solute.

Front 37

Define melting point

Back 37

The melting point of a solid is the temperature at which the solid changes to a liquid.

Front 38

What are Crystals composed of?

Back 38

Crystals are composed of particles which are arranged in a regular geometric pattern called a lattice.

Front 39

What do you call it when a solid changes directly from solid to a gas phase?

Back 39

Sublimation

Front 40

Name and discuss 2 types of crystals

Back 40

A) Metallic crystals - The particles are metal atoms surrounded by delocalised electrons. The positive atomic kernels are bonded into the lattice by the negative 'sea' of electrons.

To melt the metal requires breaking this strong bond so metals have high melting points

B) Ionic crystals - Alternating positive and negative ions are held together by attraction between opposite charges. Ionic solids have high melting points because melting requires separating the ions.

Front 41

Name 2 covalent network structures

Back 41

Diamond

Graphite

Front 42

Name one exception where the particles in liquids are molecules so intermolecular forces play a major role in the properties of liquids

Back 42

Mercury

Front 43

Discuss the difference between cohesion and adhesion.

Back 43

Cohesion - act between the particles of the liquid

Adhesion - act between the liquid particles and the particles of the container.

Front 44

What variables are used to describe a sample of gas

Back 44

1) pressure

2) volume

3) temperature

4) number of particles / moles (depends on mass)

Front 45

What formula is used to measure the pressure of gas?

Back 45

Pressure = Force / area

Front 46

State Boyles' Law

Back 46

The volume of a given mass of gas is inversely proportional to the pressure exerted on it provided the temperature of the gas remains constant.

Front 47

What happens when a gas is heated?

Back 47

As the temperature of a gas increases the particles move faster.

If the volume of the container does not change the particles will cross the container more often and the number of collisions with the sides of the container will increase.

Front 48

Define Charles' Law

Back 48

Charles' Law states that the volume of a fixed amount of gas at constant pressure is directly proportional to the temperature of the gas.

V/T = k or V1/T1 = V2/T2

V = volume of container

T = temperature of system in Kelvin

k = constant

Front 49

Discuss Gay-Luusac's Law (Pressure-temperature relationship)

Back 49

The temperature of a given mass of gas is directly proportional to its pressure provided the volume remains constant.

P/T = k or P1/T1 = P2/T2

Front 50

Explain Gay-Luusac's Law in terms of kinetic theory.

Back 50

The volume cannot change. As the temperature increases, the kinetic energy of the particles increases.

This results in more collisions with sides of the container and pressure increases.

Front 51

Convert 25 C to Kelvin

Back 51

25 + 273 = 198K

Front 52

What is Avogadro's hypothesis?

Back 52

Equal volumes of gases at the same temperature and pressure contain the same number of particles.

Front 53

What is the ideal gas equation?

Back 53

pV = nRT

Front 54

What is an ideal gas?

Back 54

An ideal gas is the model we use to explain the gas laws.

An ideal gas obeys the gas law as at all temperatures and pressures

Front 55

Discuss the differences between Ideal gases and Real gases

Back 55

Ideal gases:

> Have infinitely small particles

> All particles are identical

> Have no intermolecular forces between particles

> Collisions between particles are perfectly elastic

Real gases:

< Have particles of measurable size

< In gas mixtures particles are not identical

< Hav significant intermolecular forces

< Collisions between particles are perfectly elastic

Front 56

What happens to Real gases at high and low temperatures.

Back 56

High temperatures: the particles are large compared to the spaces between them. As pressure increases the volume can no longer decrease and it becomes constant.

Low temperatures: intermolecular forces cause the particles to stick to each other. The volume of the gas becomes constant and the pressure is lower than expected.

Front 57

What is a mole?

Back 57

The mole is used to measure quantities of substance (unit mol)

1 mol is defined as the amount of substance that contains the same number of particles as 12 g of the commonest isotope of carbon 12C

Front 58

How is mass defined according to carbon?

Back 58

1/12 of a C-12 atom as 1 atomic mass unit (amu)

Front 59

What is the empirical formula?

Back 59

The empirical formula of a substance is the basic ratio of atoms that make up that substance.

Front 60

What is the molecular formula?

Back 60

The molecular formula is the actual formula for the molecule.

Front 61

Give the formula to change mass to moles

Back 61

n = n / M

mols = sample mass / molar mass