Teaching/Learning issues

 
Topics covered in Term 1
-Introduction to Science (Tested)
-Laboratory rules (Tested)
-Scientific apparatus and their uses (Tested)
-Plotting graphs
Introduction to Science
Science around us-Industries,food,biology,equipments,defence,environment etc.

Attitudes and attributes of a scientist - Curiosity, perseverance, positive approach to failure,open-mindness,co-operation with others,tolerance,healthy scepticism,integrity,refusal to believe superstition,impartiality etc.



Safety Rules
-Used in laboratory so that no one gets injured during experiments

General rules
-Do not enter the laboratory without the teacher’s permission.
-Open all doors and windows unless otherwise instructed by your teacher
-Do not carry out any test or experiment without the teacher’s permission.
- Read the instructions first and understand them before starting any experiment.
-If in doubt, always ask your teacher.
-Handle all apparatus and chemicals carefully and correctly.
-Always check the label on the container before using the substance it contains.
-Do not pour any unused chemicals back into its container to avoid contamination.
-Do not taste any chemicals unless otherwise instructed by the teacher.
-Do not eat, drink or play in the laboratory.
-Do not tamper with the electrical mains and other fittings in the laboratory Work tidily. Wash up all used apparatus and dispose of the waste correctly
-Return the apparatus to their proper storage places after cleaning.
-Do not remove any apparatus or chemicals from the laboratory.
-Wash your hands after all laboratory work.

Safety rules when heating or mixing chemicals
-Wear goggles when mixing or heating chemicals
-Place flammable substances away from a naked flames.
-Point the mouth of a test tube or boiling tube which is being heated away from yourself or your friends
When accidents occurs
-Report all accidents, injuries, breakage and spillage to your teacher immediately.
-Should a chemical get into your mouth, spit it out into a basin and rinse your mouth with plenty of water.
-If any chemical comes into contact with other parts of your body or clothing, wash thoroughly with water and report to your teacher.


Hazard symbols
Containers of dangerous chemicals are labelled with special symbols to warn others about the hazardous nature of the chemicals.

Flammable substances Example:petrol, kerosene, alcohol
Keep flammable substances away from fire or heat

Explosive substances Example:mixture of hydrogen and oxygen
Explosive substances usually explode when heated or lit. Use them according to the instructions given.

Corrosive substances Examples:Alkali, Strong acid
Avoid direct contact with the corrosive substances which can cause burns. Wash off any spilled acid or alkali on your skin or clothes with plenty of water

Poison or toxic substances Example:mercury, cyanide, chlorine gas
Do not eat, drink or taste these poisonous substances. Use them according to the instructions given.

Irritating or stimulative substances Example:chloroform, alcohol, bromine vapour
Avoid inhaling the vapour of stimulative substances. Use them in a fume chamber

Radioactive substances Example: radioactive carbon, uranium, plutonium
Strictly adhere to all safety precautions when handling radioactive substances

Laboratory Equipment
-Many types of equipments, at least over 50
-Each equipment has a specific use, special and its own way

Examples of laboratory equipments and its uses
Test tube/Boiling tube- For containing or heating small amount of substances
Beaker/Conical Flask- For containing chemicals or collecting liquids
Flat-bottomed flask- For containing chemicals when preparing gases if the process requires no heating
Round-bottomed flask- For preparation of gases if the process requires heating
Measuring cylinder- For measuring a volume of liquid
Burette-For measuring a volume of liquid
Pipette- For measuring very accurately a specific volume of liquid, such as 10 cm3, 25 cm3 and 50 cm3
Thistle funnel- For transferring liquids into a flask
Filter funnel- For separating an insoluble solid from a liquid with the help of a piece of filter paper
Displacement can- For displaced liquid to flow out through its spout
Gas Jar-For collecting gases
Bell Jar- For separating an experimental set-up from the outside environment
Evaporating Dish- For evaporating a liquid from a solution
Crucible- For heating solids directly over a flame
Water trough- For containing water when collecting gases
Tripod Stand- For supporting apparatus during heating
Retort Stand- For supporting apparatus during experiments
Distilling Flask- For containing the liquid mixture which would distill the component liquid when heated
Liebig Condenser- To allow the distilled vapour to condense in order to collect the liquid

Bunsen burner
-Commonly found and used in the lab
-Used to heat up a certain substance to a certain temperature
-User-friendly and lightweight
Parts of the Bunsen burner and its uses
1) Barrel: to raise the flame to a suitable height for burning
2) Collar: to regulate the amount of air entering the burner through the air-holes
3) Gas tap: to control the flow of gas to the Bunsen burner
4) Air-holes: to allow air to enter the burner
5) Base: to support burner so that it will not topple
6) Jet: to enable the gas to rush out of the gas supply and to draw in air

Steps to light a Bunsen burner
1) Close the air-holes
2) Put the lighter above the barrel
3) Turn on the gas tap
4) Strike the lighter to ignite the gas
5) Open the air-hole until a non-luminous flame is obtained (Step not needed if a luminous flame is intended for usage)

Types of flames from the Bunsen Burner
Luminous Flame
-Occurs when the air-holes are closed therefore insufficient air is allowed to mix with the gas so gas does not burn completely
-Carbon particles are produced
-Orange in colour
-Appear flickering and unsteady
-Not very hot


Non-luminous flame
-Occurs when the air-holes are opened, allowing sufficient air into the burner therefore gas is burn completely
-Blue in colour
-Burns steadily
-Hotter than Luminous flame
-Hottest part of the flame is just above the tip of the dark blue zone

Strike Back!(Worst case condition)
-Occurs when there is too much air
-There is a large supply of air because the air-holes are fully opened
-Instead of burning at the mouth of the barrel, the gas burns at the jet
-When a Strike Back occurs, turned off gas immediately (Not turning off the gas would result in HUGE danger!)
-Very hot

Topics covered in term 2
1) SI Units and prefixes
2) Conversion of units
3) Reading of apparatus
4) Density
5) Mass vs Weight
6) Kinetic Particle Theory
7) Graphing techniques
8)Elements,Compounds and Mixtures (Not tested for term 2)
9)Separation techniques (Not tested for term 2)
10)Solutions and suspensions (Not tested for term 2)

 SI Units and prefixes
-Most scientific expressions has to be in SI unit

Base Quantity Name of SI unit Symbol for SI unit
Length=meter=m
Mass=kilogram=kg
Time=second=s
Electric current=ampere=A
Temperature=kelvin=K
Light intensity=candela=cd
Amount of substance=mole=mol


Prefix Symbol Factor
nano‐ n=10‐9 (1/1000000000)
micro‐ μ=10‐6 (1/1000000)
milli‐ m=10‐3 (1/1000)
centi‐ c=10‐2 (1/100)
deci‐ d=10‐1 (1/10)
kilo‐ k=103 (1000)
mega‐ M=106 (1000000)
giga‐ G=109 (1000000000)

Conversion of units
-Used to convert any unit to the SI unit for scientific expression
-Important to show clear workings when doing conversion of units

Reading of apparatus
Common apparatus
-Meter rule: to nearest: 0.1 cm
-Vernier caliper: to nearest: 0.01 cm
-Micrometer screw gauge: to nearest: 0.001 cm
-Measuring cylinder:nearest: 1ml
-Syringe:0.1ml
-Beaker:10ml
Important!-Remember to read the meniscus at eye level when taking the volume of any liquid
            -Be careful of parallax error and zero error when reading the vernier caliper/micrometer screw gauge
                -Round off to 3 significant figures if the ans has recurring decimals

Density
Density=mass/volume
-If an object has a higher density than the liquid/solution it is in, it will sink and vice versa
-Take note of the units when dividing the mass by volume
-Round off to 3 significant figures if the ans has recurring decimals
-Always remember that water has a density of 1g/cm3

Mass vs Weight
Mass
-The amount of matter in a body

-A physical property of the object that does not change
-SI Unit: kilogram (kg)

-Measured using electronic balance or beam balance
Weight
-The amount of gravitational pull on a body
-Will vary according to the gravitational pull
-SI Unit: Newton (N)
-Measured using a spring balance
Note:Most questions will require you to leave your answers in Mass;not weight


Kinetic Particle Theory
-States that all matter is made up of tiny particles that are in constant random motion
 Solid
-Definite volume
-Definite shape
-High density of all
-least expansion upon heating
-Cannot be compressed
-Particles are closely packed and arranged orderly
-Attraction between particles are very strong
-Very low kinetic energy
Liquid
-Definite volume
-Indefinite shape
-Lower density than most solids;Higher density than most gases
-More expansion than most solids upon heating;Less expansion than most gases upon heating
-Cannot be compressed
-Particles are closely packed(less closely packed than solids) and arranged disorderly
-Attraction between particles are quite strong
-Kinetic energy is low
Gas
-Indefinite volume
-Definite shape
-Lowest density of all
-Most expansion upon heating
-Can be compressed
-Particles are loosely packed and arranged extremely disorderly
-Attraction between particles are extremely weak
-Kinetic energy is very high

Graphing techniques

-Title of graph (e.g. graph of temperature/°C against time/s) – always dependent
variable against independent variable
- Axis with units – dependent variable is always on vertical axis, independent variable
is always on horizontal axis
- Points marked with neat crosses
-Points must take up at least 2/3 the graph paper
- Draw a straight line or smooth curve/the line of best fit
- Do not "join the dots"
- No jagged or thick lines

-To solve for unknown value, draw 2 neat dotted lines on the graph, then read off the graph

 Topics covered in Term 3
1)Elements,Compounds and Mixtures
2)Separation techniques
3)Solutions and Suspensions
4)Cells (Not tested)
5)Photosynthesis (Not tested)
6)Respiration (Not tested)
7)Diffusion and Osmosis (Not tested)

Elements, Compunds and Mixtures
-Element is a a substance which cannot be broken down into two or more simpler substances by chemical methods
-ALL elements are classified in the periodic table and have a unique chemical symbol and atomic number
-Elements in the same group in the periodic table have similar chemical properties
-Across the period of the periodic table, the properties of elements change from metallic to non‐metallic
Metals
-Appear shiny
-Good conductors of electricity
and heat
-Generally high except for mercury
-Malleable and ductile
-Generally high
-Sonorous
Non-metals
-Dull
-Poor conductors of electricity and heat(except graphite)
-Generally low
-Brittle
-Generally low
-Non‐sonorous

Compounds
-contains 2 or more elements chemically joined together
-All compounds have their own unique chemical formula
-Formed by chemical reaction which usually involves heat and light
-Can only be broken down by chemical methods eg. electrolysis
-Different elements in a compound are joined together in a fixed proportion by mass
-Does not have properties of constituent elements
-Melting point and boiling point is fixed


Mixtures
-Consist of 2 or more substances (elements and/or compounds) that are mixed, but not chemically combined
-Can exist in all 3 states of matter
-Does not require chemical reaction to be formed
-Can be broken down by physical methods eg. Filtration,Distillation etc.
-Elements in a compound are joined together in an unfixed proportion
-Have properties of constituent elements
-Melting point and boiling point is over a range of temperature

Solutions and suspensions
-A solution is a mixture formed when one or more solutes dissolve in a solvent
 -The solute is the substance that dissolves
 -The solvent is the substance which the solute dissolves in, and is usually the main part of the solution
-A suspension is a mixture in which solid or liquid particles are suspended in a liquid or a gas

Solutions
-Nothing happens when passed through a piece of filter paper
-Nothing happens when it is left to settle
-Is homogenous
-Most light can pass through it

Suspensions
-Solid particles are trapped on filter paper when passed through a piece of filter paper
-Solid particles settle on the bottom of the beaker when it is left to settle
-Is not homogenous
-Little light can pass through it


Solubility
The solubility of a substance in a solvent is the maximum quantity of that substance which can dissolve in a given quantity of the solvent at a given temperature (usually given in g/100ml – e.g. Copper(II) sulfate has a solubility of 32 g/100 ml (at 20°C))


Solubility is dependent on
• Nature of solvent (e.g. iodine can dissolve well in ethanol but not in water)
• Nature of solute (e.g. iodine cannot dissolve well in water but sodium chloride can)
• Temperature of solvent (e.g. more solute can dissolve at higher temperatures)
• Pressure of surroundings (e.g. less solute can dissolve at higher pressures)


Solubility is not related to the RATE of dissolving – which is how fast a solute dissolves in a
solvent
• The rate of dissolving is dependent on
• The rate of stirring (the more vigorous the stirring, the faster it dissolves)
• The surface area of the solute (the larger surface area, the faster it dissolves – this is why fine sugar dissolves faster than sugar cubes)
• Temperature (the higher the temperature, the faster it dissolves)

Separation techniques

Types of separation techniques
• Filtration
• Evaporation to dryness
• Crystallisation
• Distillation
• Fractional distillation
• Reverse osmosis
• Magnetic separation
• Separating funnel
• Chromatography

Filtration
Use:To separate insoluble solids from the liquid in a solid-liquid mixture
Materials needed:-Beaker
                           -Filter funnel
                           -Filter paper
                            -Container containing the mixture

Steps to carry out experiment:
1)Place the filter funnel over the conical flask.
2)Fold the filter paper into the shape of a cone and place it inside the filter funnel.
3)Moisten the filter paper with distilled water
4)Pour the mixture into the filter funnel slowly.
5)Residue and filtrate are obtained

Evaporation to dryness
Use:To separate dissolved solids from a solution that does not decompose when heated
Materials needed:-Evaporating dish
                           -Wire gauze
                           -Tripod stand
                           -Bunsen Burner
Steps to carry out experiment:

1.Pour the solution into an evaporating dish.
2.Heat the solution to dryness to evaporate away the solvent, leaving behind the solute.
3.Make the Bunsen flame smaller when almost all the solvent has been evaporated away to reduce spitting.

Crystallization
Use:To separate dissolved solids from a solution whether it decomposes when heated or not.
Materials needed:(Same as Evaporation to dryness(refer to  top) but with filter paper)
Steps to carry out experiment:
1. Heat the solution to evaporate some of the water to obtain a hot and saturated solution.
2. Allow the solution to cool. As less solute is dissolved at lower temperature, crystals are formed on cooling.
3. Filter the crystals. Wash the crystals with a little cold deionised water and dry them by squeezing them between sheets of filter paper.

Distillation
Use:To separate a pure liquid from a solid-liquid or liquid-liquid mixture
Materials needed:-Tripod Stand
                           -Bunsen Burner
                           -Boiling Chips
                           -Distilling Flask
                           -Thermometer
                           -Liebig Condenser
-Receiver(Beaker)
Processes involved in Distillation
-Boiling
-Condensation
Types of Distillation
-Simple Distillation
-Fractional Distillation
Fractional Distillation
-Used to separate two or more miscible liquids
-Has a fractionating column that separates liquids in order of boiling points
-Uses the same concept of Distillation

Reversed Osmosis
Use:For Desalination
Materials needed:-Beaker
                           -Semi-permeable membrane
                           -Pressure
Steps to carry out Reversed Osmosis(desalination)
1)High pressure (about 26 times more than atmospheric pressure) is applied on sea water, causing the direction of flow reverses. It means water starts flowing from the sea water side to the fresh water side of the membrane.

Magnet separation
Use: To separate magnetic objects
Materials need:-Magnet
-To carry out experiment, put the (electro)magnet over  the mixture which you wish to obtain magnetic objects from

Separating Funnel
Use:To separate two immiscible liquids-liquids
Materials needed:-Beaker
                           -Funnel
                           -Filter paper
-To carry out experiment, put mixture inside funnel with filter paper surrounding it

Chromatography
Use:to separate the different components in a liquid or gaseous mixture.
Materials needed:-chromatography paper
                          -Boiling tube
                          -A clip, pin etc to make the chromatography paper suspend in mid-air
Steps to carry out experiment:
1.Apply a small but concentrated spot of the solution on a piece ofchromatography paper.
2.Suspend the chromatography paper in a beaker or boiling tubeof solvent with the spot above the level of the solvent.
3.As the solvent travels up the paper, the mixture is separated into its respective components.A chromatogram of the separated components is obtained.