Grade 11 Physical Sciences Summaries. This summaries are composed using the Via Afrika textbooks' term 2 work with examples and supplementary notes.
Chapter 3: Waves, Sound and Light
Unit 1: Geometrical Optics
Unit 2: 2D & 3D Wavesfronts
Chapter 4: Matter and Materials
Unit 1: Id...
Reflection:
• Incident ray = ray going towards mirror.
• Reflected ray = ray coming from mirror.
• Normal = imaginary line perpendicular to surface
from which the light is reflected.
• Angle i = angle of incidence.
• Angle r = angle of reflection.
• Laws of reflection:
- Angle of incidence = angle of reflection.
- Incident ray, normal and reflected ray are all
in the same plane.
U1:
Sample
Geometrical
Refraction: Snell’s Law:
Optics (A)
• Refraction = the change in the direction of
light when it enters a new medium. • If ray of light enters glass with angle
• Light slows down when it enters glass and of incidence θ1.
then speeds up when it enters air again. • Angle of refraction (θ2) is smaller than
Summaries after sample
•
•
Optical Density:
• The more the light slows down, the
Refractive Index:
• Speed of light is constant when
passed through given medium.
θ1.
• θ2 will increase if θ1 increases, but
they aren’t directly proportional.
𝑠𝑖𝑛𝜃
• n = 𝑠𝑖𝑛𝜃1 .
2
• n1 sinθ1 = n2 sinθ2.
• Refraction index = ratio of velocity of
greater the amount of refraction.
light in space (c) to velocity of light in
• Optical density = degree to which the
medium (v).
medium slows the light down. 𝑐
• n=𝑣.
• Beam of light composed of parallel
transverse waves enters glass at an • When light enters medium of greater
angle of incidence of 0°: optical density at an angle:
- Doesn't deviate. - Frequency stays constant.
- Wavelength decreases. - Period stays constant.
• When a beam strikes glass at an angle: - Speed decreases.
- Beam refracts towards normal - one - Wavelength decreases.
side of beam slows down first. - Bends towards normal.
, Motion of Particles:
Gay-Lussac’s Law:
• Gay-Lussac's law = The pressure of a fixed
mass of gas with a constant volume is directly
proportional to the temperature.
• Temp. is increased – particles have more
energy – exert greater pressure on container.
𝑝 𝑝
• 1= 2.
𝑇1 𝑇2
𝑝1 𝑉1 𝑝2 𝑉2
• Combination of the laws: 𝑇1
= 𝑇2
. Behaviour of Non-
• Avogadro’s principle = equal volumes of Ideal Gases:
different gases at the same temp. and
Sample pressure will contain the same no. of particles. • Particles of real gas occupy space – low
temp. causes volume of real gas to be
U1: Ideal Gases more than ideal gas.
• Real gases can’t be compressed to
& Thermal expected volume when the pressure is
• Ideal Gas Equation: Properties (B) high – V is greater, so pV is also greater.
Summaries after sample
•
• Combines Boyle’s law and Charles’s
relationship.
• V∝𝑝.
𝑇
SI Units & the Ideal
• High pressure causes particles to become
closer - real volume of particles come into
effect.
• Ideal gas law can’t be used under very low
temps. or very high pressure.
• pV = nRT.
Gas Equations:
• Pressure = Pa.
- 1kPa = 1000Pa.
• Volume = m3 – usually given in dm3 or ℓ.
- 1ℓ = 1dm3 = 0,001m3.
• Temp. = K – usually given in °C.
- K = °C + 273.
, Relationship Between
Volume Relationships Volume, Temp. & Pressure:
in Gaseous Reactions: • More accurate value for volume of
gas used can be calculated using the
Ammonium Nitrate in Mining: general gas equation (pV = nRT) if
Functioning of Airbags:
actual values of pressure and temp. • Object hits airbag position with enough force
• 2NH4NO3(s) (in presence of heat) -> 2N2(g) +
are known. – sensor causes electrical spark.
4H2O(g) + O2(g).
• E.g. 10g of NH4NO3 used. 2 moles of solid NH4NO3 • Spark ignites small sodium azide pellet.
produces (2 + 4 + 1) moles gas. How to calculate • 2NaN3(s) -> 2Na(s) + 3N2(g).
volume of gas produced: • Nitrogen gas rapidly fills airbag – causes it to
𝑚𝑎𝑠𝑠
- nammonium nitrate = 𝑀 = 10g ÷ (14 + 4 x 1 + 14 + 3 burst out of the dashboard or steering wheel.
Sample
-
-
-
10
x 16) = 80= 0,125 mol.
2 mol NH4NO3 -> 7 mol gas.
0,125
0,125 mol NH4NO3 -> 2 x 7 = 0,438 mol gas.
Volume gas produced at STP = 22,4 x 0,438 =
U1: Quantitative
Aspects of Chemical
Change (C)
• Sodium azide is harmful – KNO3 also placed
into airbag to react with sodium:
10Na(s) + 2KNO3(s) -> 2K2O(s) + N2(g).
• Reaction is exothermic – volume of nitrogen
produced will be larger than what is
Summaries after sample
9,81dm3. calculated, at resulting higher temp.
• E.g. if airbag must inflate to a volume of
27dm3:
27
- 22,4 mol N2 gas required to get a volume
Petrol in a Car Engine: of 27dm3.
27
• 2C8H18(g) + 25O2(g) -> 16CO2(g) + 18H2O(g). - = 1,21 moles N2.
22,4
• Octane and oxygen are sucked into the cylinder – - 2mol NaN3 produces 3 mol N2:
1,21
mixture is compressed by pistons pushing into *1,21 mol N2 produced from 3 x 2mol
cylinder – reduces volume. NaN3 = 0,81mol NaN3.
• Spark produced by spark plug – causes reaction *Molar mass (M) of sodium azide is [23 +
between oxygen and fuel. 3 x 14] = 65g.mol-1.
• Large production of CO2 and water vapour causes *Mass NaN3 required = n x M = 0,81 x 65
explosion – gas explosion pushes piston down = 52,7g NaN3.
again – process restarts. *Compressed into pellet.
-
, Reflection:
• Incident ray = ray going towards mirror.
• Reflected ray = ray coming from mirror.
• Normal = imaginary line perpendicular to surface
from which the light is reflected.
• Angle i = angle of incidence.
• Angle r = angle of reflection.
• Laws of reflection:
- Angle of incidence = angle of reflection.
- Incident ray, normal and reflected ray are all
in the same plane.
U1:
Geometrical
Refraction: Snell’s Law:
Optics (A)
• Refraction = the change in the direction of
light when it enters a new medium. • If ray of light enters glass with angle
• Light slows down when it enters glass and of incidence θ1.
then speeds up when it enters air again. • Angle of refraction (θ2) is smaller than
• θ1.
•
Refractive Index: • θ2 will increase if θ1 increases, but
they aren’t directly proportional.
Optical Density: • Speed of light is constant when 𝑠𝑖𝑛𝜃
• n = 𝑠𝑖𝑛𝜃1 .
passed through given medium. 2
• The more the light slows down, the • n1 sinθ1 = n2 sinθ2.
• Refraction index = ratio of velocity of
greater the amount of refraction.
light in space (c) to velocity of light in
• Optical density = degree to which the
medium (v).
medium slows the light down. 𝑐
• n=𝑣.
• Beam of light composed of parallel
transverse waves enters glass at an • When light enters medium of greater
angle of incidence of 0°: optical density at an angle:
- Doesn't deviate. - Frequency stays constant.
- Wavelength decreases. - Period stays constant.
• When a beam strikes glass at an angle: - Speed decreases.
- Beam refracts towards normal - one - Wavelength decreases.
side of beam slows down first. - Bends towards normal.
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