PHYSICAL SCIENCES 2/2
GRADE 11
November
PHYSICAL SCIENCES 2/2
GRADE 11
November Exam study notes was compiled by using at 2019 – 2021 DBE/ SACAI previous examination papers. The notes are compact, colourful and easy to study, making it perfect for learners with learning barriers.
Topics:
M...
PHYSICAL SCIENCES 2/2
GRADE 11
November
2023
These notes were compiled using past exam papers: SACAI JUN 2019/Nov 2021/ JUNE 2022
Multiple-choice questions
CH4 molecule This molecule is non-polar, even if it has at least one polar bond
CH3Cl This substance that has polar bonds, a polar molecule and tetrahedral shape.
Trigonal bipyramidal The molecular geometry of a molecule that has five bonding pairs around
the central atom.
Lewis diagrams of BH3
Lewis diagrams of NH3
Ion-dipole forces Sodium hydroxide (NaOH) dissolves in distilled water (H2O). The
intermolecular forces that are responsible for this observation, is Ion-dipole
forces
The Lewis diagram above represents an argon atom or a sulphide ion
A chemical bond A chemical bond can be defined as a common attraction between two atoms
that results in the simultaneous attraction between their nuclei and outer
electrons
Ideal gas Characteristic of an ideal gas identical particles that have no volume.
Real gases deviate from ideal gas behaviour at high temperature and low pressure.
At STP, 44 g carbon dioxide, CO2, will have the same number of molecules as 30 g of ethane, C2H6
When atoms move closer than bonding length, to each other the potential energy will increase.
The following quantities of substances represents one mole:
Number of protons in 1 g Hydrogen gas.
, The molecular form of a molecule with the formula AB2 is linear or angular.
The boiling point of CH4 is much lower than that of HF.
Explains this difference in boiling point the best = There are hydrogen bonds between HF-molecules.
1 mol of helium gas at STP has the following volume
2,24 x 104 cm3
R = An acid
A compound with the formula XO2 has a relative formula mass of 64
Represented by X = Sulphur
You might get similar questions in the exam, try to answer it without looking at the answers.
, Matter and materials
Question (SACAI JUN 2022)
Study the two compounds BH3 and NH3.
Comparing the polarity of the BH3- and NH3-molecules by referring to the polarity of the bonds and
the effect of the shape of each molecule on its polarity.
NH3
• pyramidal
• Has a lone pair and 3 bonding pairs.
• Polar molecule
• Asymmetrical shape
BH3
• trigonal planar
• has only 3 bonding pairs.
• Non-polar molecule Sy
• symmetrical shape
Dative covalent bond
The name of the bond that forms between the nitrogen atom in NH3 and a hydrogen ion (H+).
The table below shows the bond length and bond energy for different bonds between two carbon
atoms.
The relation between bond length, bond order and bond energy
• As the bonding order/bonding pairs increases, the bond length decreases and the bonding
energy increases.
, • As the bonding order / bonding pairs decreases, the bond length increases and the bonding
energy decreases
C is the strongest because Has the highest bonding energy and the lowest bonding length.
Question (SACAI JUN 2022)
Why ethanol dissolves in water
• Ethanol and water both have hydrogen bonds.
• Intermolecular forces are the same in relative strength.
The boiling point of a liquid
The temperature where the vapour pressure of the liquid equals the atmospheric pressure.
The reasons why the boiling point of bromine is lower than the boiling point of iodine.
• Br2 and I2 both have London/dispersion/induced dipole forces
• I2 molecular mass / molecular volume is larger than that of Br2
• I2 needs more energy to overcome intermolecular forces and therefore has a higher boiling
point.
The reasons why phosphine evaporates faster than ammonia referring to the type and strength of
intermolecular forces.
, ➢ NH3 has hydrogen bonds and PH3 has dipole-dipole bonds
➢ Hydrogen bonds are stronger than dipole-dipole bonds.
➢ Ammonia needs more energy to overcome the intermolecular forces and therefore has a higher
boiling point.
➢ Ammonia has a higher boiling point and therefore evaporates slower.
Question (SACAI JUN 2022)
The relation between the pressure and volume of oxygen gas is investigated at standard temperature.
For the experiment 0,5 mol oxygen gas is placed in a sealed container. The volume of the container is
slowly decreased at standard temperature. A set of readings of V versus p is notated and represented
on a graph. On the same graph the graph for an ideal gas is also given.
The gas law
Boyle’s law. The pressure of an enclosed gas is inversely proportional to the volume of the gas if the
temperature remains constant. The volume of a given mass of an enclosed gas is inversely
proportional to the pressure if the temperature is kept constant.
Calculate the value of V1 on the graph.
, A mixture of fuel and air, with a volume of 125 cm3, is sucked to the cylinder of a motorcycle, when
the piston reaches the end of its stroke. The initial temperature is 27 °C and the pressure is 100 kPa.
The gas is compressed to a volume of 50 cm3 and reaches a temperature of 77 °C before it explodes.
Calculate the pressure in the cylinder just before the explosion.
Question (SACAI JUN 2019)
Nitrogen is a gas that makes up the largest percentage of the air-mixture that
we breathe.
Valence electron = Valence electrons are electrons that are found in the highest/ outer most/ furthest
energy level.
How many valence electrons do a nitrogen atom have? 5
The bond between nitrogen atoms are non-polar
, • There no nett-dipole moment
• no uneven charge distribution
• EN = 0
• qual distribution of charge/ atoms attracts electrons with equal strength
• symmetric molecule
The oxygen in air can bond with hydrogen to form water.
A water molecule polar
The water molecule is angular, (thus no nett-dipole moment.)
• ENV = 3,5 -2,1 =1,4
Nitrogen gas is insoluble
Nitrogen gas has London forces thus non-polar and water is polar. Only substances with similar/same
IMF strength will dissolve.
A nitrogen atom has the ability to share a lone electron pair with a
hydrogen ion.
This type of bond is called a Dative covalent bond
A Lewis diagram of the ammonium ion that is formed during this type of bond
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