TMSI Math & Science Study Notes: January 2020

The following is a list of common apparatus and equipment found in most Chemistry school laboratories (there are 44 items):

Safety goggles

Safety is the most important thing to observe in a science laboratory. You need to follow safety rules once you step into a laboratory.

Safety googles should be worn at all times. Wearing safety googles prevents irritation of the eyes and prevents blindness in case of an incident such as the splashing of acids.

Test tube, test tube rack, test tube holder, test tube brush

Test tubes are glassware that are used to hold, transfer or mix chemical substances. They are held in test tube racks. If the test tube needs to be heated, a test tube holder is used to handle them rather than using bare hands. Test tube brush are used to clean test tubes with stubborn deposits.

Boiling tube

Boiling tubes are similar to test tubes except they are slightly larger.

Precaution when heating test tubes and boiling tubes

Wear safety googles to protect the eyes from any irritation or harm due to splashing of hot or corrosive liquids.
Use a test tube holder to hold a test tube or boiling tube during heating.
Point the mouth of the test tube or boiling away from yourself and any other person. This can help to prevent spillage of chemical on someone else.

Funnel, filter paper

Funnels are commonly used with filter paper to separate insoluble solid particles from a solution or liquid when carrying out filtration. The solid particles may be precipitates formed from a precipitation reaction or from the use of excess solids in acid reactions.

Funnels are also used to transfer liquids into another container with small opening without spilling the liquids.

They are also used to demonstrate sublimation by providing a cooler surface for the deposition of vapour such as iodine.

Filter papers are also used in paper chromatography experiment for separating complex mixtures of solids such as dyes and amino acids.

Spatula

Spatulas are used for transferring small amount of solid substances.

Stirring rod

A stirring rod is used to stir solutions to mix up substances well to ensure all reactants are completely reacted (reaction goes to completion) or to speed up the rate of chemical reaction by increasing the chances of reactants being exposed to one another.

Other uses of stirring rods:

Assists in pouring liquids by reducing spillages
Transfers a single drop of solution
Tests if a solution is saturated. If the stirring rod is dipped into a hot concentrated solution and crystals are seen to form on it, the solution is saturated.
Scrape crystals off an evaporating dish from a crystallisation process

Beam balance (double beam balance, triple bean balance)

The triple beam balance is a scale that gives an accurate reading of mass using three beams, each marked with different gram increments. The smallest beam is the most precise, measuring increments from 1 to 10 grams. The middle beam measures in increments of 10 grams and the largest beam measures in increments of 100 grams. To use it, start with the largest beam and work your way down to the smallest beam. Each beam has a weight that can move back and forth. When the weights are being adjusted, the pointer at the end of the beams moves up and down. When the pointer reaches the zero mark, the mass of the substance is ready to be recorded. Accuracy = 1g.

Electronic balance

An electronic balance is used to accurately measure the mass of a substance. It is a sensitive instrument that is calibrated for use in a particular position.

Steps for using an electronic balance
1. Put an empty container such as a petri dish, weigh boat or a small beaker on the balance.
2. Press the "TARE" or "zero" button on the balance.
3. Remove the container from the balance and place the chemical you require into container. .
4. Place the container again on the balance and record the mass reading that is displayed.

Typical accuracy = 0.001g. As the electronic balance is more accurate and sensitive than the beam balance, you will more commonly use this equipment

Precaution

Do not place the substance to be measured directly onto the balance plate. Use a container such as a petri dish, weigh boat or a small beaker. The balance is sensitive, and any residue left on the balance will affect the next reading. If the substance is corrosive, the balance plate will also be affected and will not be able to measure accurately.
Do not add chemicals to the container while it is still on the balance. If you spill any substances onto the balance, the measurement of mass will no longer be accurate. Remove the container and then add the chemical into it.
Ensure that the balance is set to zero before taking the final mass measurement.

Wash bottle

Wash bottle contains distilled or deionised water. They are used to wash solution residues off solid precipitates to obtain a clean sample.

Beaker

Beakers are used to hold, mix or heat solid or liquid samples. Even though there are volume markings on them, they are not used for measuring accurate volumes of liquids.

Measuring cylinder/Graduated cylinder

Measuring cylinders are used to measure liquid volumes and they come in a variety of sizes. The 0cm³ marking starts at the bottom. Accuracy = 1cm³ or 1ml.

Measuring cylinders are also used to collect the water displaced from a water displacement can (also known as Eureka can) procedure to find the volume of an irregular solid.

Burette

A burette has an opening at the top and a narrower opening at the lower end. One type of burette has a rubber tubing used in tandem with a rubber clip.

Burettes are used to measure an accurate volume of liquid. One common size is the 50.00 cm³ burette. and the 0.00cm³ marking starts at the top. Accuracy = 0.1cm³, but recording of volume is rounded up to the nearest 0.05cm³.

Steps for using a burette
1. Ensure that the rubber tubing at the lower end is clipped.
2. Pour liquid or solution from the top using a funnel if necessary to prevent spillage. Stop when the liquid or solution is above the 0cm³ marking. Remove the funnel.
3. Open the rubber clip at the bottom to release small amount of liquids at a time until the meniscus reaches the 0cm³ marking. This will also help to remove air in the rubber tubing.
4. Using a clamp, secure the burette on a retort stand.
5. Record the initial volume, Vi.
6. Place a container such as a conical flask below the rubber tubing.
7. Open the clip to release the liquid into the container.
8. When a specific volume of liquid has been released, close the clip.
9. Record the final volume, Vf.
10. Calculate the volume of liquid released by subtracting the initial volume from the final volume, Vf - Vi.

Precaution

When reading the volume, ensure the eyes are at the same level as the meniscus to prevent parallax error.
Read the correct position of the meniscus. If the meniscus curves downwards, the volume is read as the bottom of the meniscus. If the meniscus curves upwards, the volume is as the top of the meniscus.
It is important to release excess liquid or solution from the rubber tubing to remove any trapped air in the tubing.

Pipette, pipette filler

Pipettes are used to measure an accurate exact volume of liquid which is to be transferred to another container. There is a line indicating exactly where you need to fill the liquid up to.

Pipettes come in a variety of sizes. A common size is the 25.0cm³ pipette. The .0 decimal place must be stated when you are asked for the the size of the pipette. Therefore, accuracy = 0.1cm³ .

Pipettes are used with a pipette filler to suck up a liquid, much like the bulb in a dropper (explained below). The pipette filler is a 3-way bulb.

Steps for using a pipette
1. Pour the liquid to be measured into a beaker.
2. Insert the pipette filler into the top of the pipette.
3. Squeeze the air valve (A) and the bulb simultaneously to force as much air out as possible.
4. Dip the other lower end of the pipette into the liquid to be measured.
5. Squeeze the suction valve (S) to draw liquid into the pipette until the meniscus is at the right position at the line marking.
6. Remove the pipette from the liquid.
7. If you need to remove excess liquid from the pipette, bring the pipette to sink area and squeeze the empty valve (E) to remove the excess liquid. Precaution: do not squeeze the liquid back into the sample to avoid contamination.
8. Place the opening tip of the pipette on the side of a beaker or flask (this prevents spillage). Squeeze the empty valve (E) until all liquid is forced out of the pipette.

Precaution

When using the suction valve (S), do not allow any liquid to enter the pipette filler.
When reading the volume, ensure the eyes are at the same level as the meniscus to prevent parallax error.
Read the correct position of the meniscus. If the meniscus curves downwards, the volume is read as the bottom of the meniscus. If the meniscus curves upwards, the volume is as the top of the meniscus.

Dropper/Teat pipette

A dropper is a small narrow glass tube with a narrow tip at the open end and a rubber bulb on the other. It is used to suck up a small amount of liquid that can be squeezed out drop by drop using the bulb.

Steps for using a dropper
1. Prepare liquid sample in a beaker.
2. Squeeze the rubber bulb. The more air you squeeze out of it, the more liquid you can suck up.
3. Dip the narrow tip into the liquid and release the squeeze on the bulb.
4. Remove the dropper from the liquid.
5. To push liquid out from the dropper. squeeze the bulb gently.

Precaution

When sucking up the liquid, do not allow any liquid to enter the bulb. If you are unsure of the amount of pressure to apply, try to squeeze less air in the beginning, note the amount of liquid being suck up and squeeze more the next time if it is not sufficient.

A dropper is commonly used to add a few drops of pH indicator in a titration experiment to indicate the end-point or to add a few drops of aqueous sodium hydroxide or aqueous ammonia for testing cations.

Conical flask (Erlenmeyer flask)

A conical flask is a glassware with a small narrow neck that gradually expands towards the bottom. It is used to hold liquids but not used for volume measurements.

What it is used for

Its small opening which makes it more suitable to collect condensed liquids in a distillation experiment because a smaller exposed surface area results in a smaller rate evaporation. This is especially important for volatile liquids.
Its small neck and large bottom also makes it easy to swirl and mix liquids while reducing the risk of splashing, such as during a titration experiment.
It is also commonly used for mixing substances that react to produce a gas.

Round-bottomed flask/Boiling flask/Florence flask/Distillation flask

A round-bottomed flask has a round bottom and a long narrow neck which makes it easy to swirl and mix liquids. The round bottom helps to spread out heat evenly while the narrow neck helps to prevent splashing.

Volumetric flask

Volumetric flasks measure a precise specific volume of liquid. There is a line on the neck of each flask indicating exactly where you should fill the liquid up to.

It is commonly used to prepare standard solutions. A standard solution is one with specific concentration.

Precaution

When reading the volume, ensure the eyes are at the same level as the meniscus to prevent parallax error.
Read the correct position of the meniscus. If the meniscus curves downwards, the volume is read as the bottom of the meniscus. If the meniscus curves upwards, the volume is as the top of the meniscus.

Evaporating dish

An evaporating dish is a heat-resistant ceramic container that is used for evaporating non-volatile solutions to obtain dry crystals.

Watch glass

An watch glass is a convex-shaped glassware for holding a small amount of solid. It is also used as a cover for an evaporating dish or a beaker.

Crucible and lid, crucible tongs

A crucible is a ceramic cup-shaped container that can withstand high temperature and is used to heat substances. The lid can contain any smoke particles.

It is not safe to touch a heated crucible by hand as you will risk burning your skin. A safe way is to use a crucible tongs to handle the crucible.

Bunsen burner

Bunsen burners are used for heating non-volatile liquids and solids. Many chemistry experiments or analyses involve heating such as carrying out crystallisation, distillation, combustion and thermal decomposition.

Parts of a Bunsen burner

Part	Purpose
Gas valve	To open or close, and control the amount of gas supply
Gas hose	To transfer gas from the gas valve to the Bunsen burner
Base	1. Made of an heat-insulating material to insulate the hot Bunsen burner from the table 2. Provides an insulated part for moving the burner around 3. Provide a relatively large base area for stability
Collar	Can be rotated to control the size of air-hole
Air-hole	Enables air to enter the barrel
Gas Jet	Enables gas to escape and mix with air
Barrel	Raise the flame to a suitable height for heating

Precaution

Put on safety goggles
Ensure there are no flammable chemicals near the Bunsen burner.
If you need to move the Bunsen burner, move it using the rubber/insulated base. Do not touch the metal barrel which can be still hot.

Steps for using a Bunsen burner
1. Ensure that the gas hose is connected from the gas tap to the Bunsen burner and the air-hole is closed completely.
2. Turn on the gas supply by turning the gas tap.
3. Ignite the gas at the top of the barrel using a striker. The gas will be luminous at first.
4. If the flame is too big, adjust the gas tap to reduce the amount of gas flowing.
5. Open the air-hole until the flame becomes non-luminous.

When you are not actively using the Bunsen burner,
1. Close the air-hole
The luminous flame that is formed is more visible and less hot. This reduces the chance of accidents happening due to not being able to see the flame.
2. Turn off the Bunsen burner completely by closing the gas tap completely.

There are 2 types of flames: luminous and non-luminous flame.

Luminous flame	Non-luminous flame
Orange-yellow	Blue
Formed when oxygen supply is insufficient (when air-hole is closed)	Formed when oxygen supply is abundant (when air-hole is opened)
Moderately hot	Very hot (high temperature)
Flickering and unsteady	Steady
Produces soot	Burns cleanly

Components of luminous flame:

The flame is orange due to carbon (soot) particles produced from incomplete combustion burning in the air.

Components of non-luminous flame:

Notice that the cooler the colour, the hotter the part is.

Tripod stand

A tripod stand is a three-legged platform for supporting flasks and beakers during heating with a Bunsen burner, usually with a wire gauze.

Wire gauze

Wire gauze provides a surface for a beaker or flask to rest when being heated by a Bunsen burner. It also helps to distribute heat evenly.

Clay triangle

A clay triangle is used to hold a crucible on a tripod stand or ring stand while it is being heated by a Bunsen burner. Alternatively, place the crucible on a wire gauze prior to heating if a clay triangle is unavailable.

Retort stand and clamps

A variety of clamps can be attached to retort stands to hold different apparatus.

A test tube clamp is used to hold test tubes, distillation flasks/boiling flasks, and distillation columns while a burette clamp can hold a burette.

Hot plate

Hot plates are used as sources of heat when Bunsen burner flame is not desirable, such as heating a volatile liquid. Some hot plates come with a stirrer that enables to swirl the containers at the same time while they are being heated. This is very convenient for carrying out rates of reaction experiments.

Water bath

A water bath is an equipment that maintains water at a constant temperature in a container.

Condenser/Liebig condenser

A condenser collects and condenses vapour into liquid efficiently by providing a cool elongated inner surface through the flow of a cooling liquid.

Delivery tube

Delivery tubes transfer from one container to another. They can be made of glass, plastic or rubber. They are commonly used, for example, in experiments that produce carbon dioxide gas, in which the delivery tube transfers the gas into test tube that contains lime water (aqueous calcium hydroxide) to observe that a white precipitate (calcium carbonate) is formed.

U-tube

A U-tube is usually used with a drying agent to remove moisture (water) from a gas mixture.

Water trough

A water trough is used for containing water for gas collection.

Gas jar

A gas jar is used for storing or transferring gases.

Beehive shelf

A beehive shelf is made of ceramic and is used to support a gas jar while a water-insoluble gas is being collected from an experiment.

Thistle funnel

A thistle funnel consists of a long narrow tube with a funnel-like section at the top. It is used to add small amounts of liquid to an exact location.

Rubber stopper

Rubber stoppers are used to close the openings of test tubes and flasks to prevent the evaporation of liquids or escape of gases, such as the limewater test for carbon dioxide gas.

Gas syringe

A gas syringe is used to collect and measure the volume of gas.

Liquid-in-glass thermometer

Thermometers are frequently used in reactions that involve heat exchange. For example, neutralisation is an exothermic reaction and you may be used to record the temperature rise of such an experiment. You may also be using thermometers to determine the melting or boiling points of substances. Thermometers are also used to monitor the progress of distillation to see which is the current substance being distilled.

There are different types of thermometers. Liquid-in-glass thermometers use the thermal expansion property of liquids as a measure of temperature. Examples of liquid-in-glass thermometers mercury-in-glass thermometer and alcohol-in-glass thermometers. In your chemistry laboratories, the mercury-in-glass thermometer is more common as it is able to measure as high as the boiling point of water (100 °C). Alcohol-in-glass thermometers are typically used to measure indoor house temperatures and body temperature.

They measure temperatures in degree Celsius, °C. Accuracy = 0.1 °C.

Separating funnel

A separating funnel has a huge section in the middle that tapers towards the bottom. It has a tap at the bottom so that after the liquids have settled into different layers, the tap can be opened to allow the liquid with the higher density to be separated. The narrow end enables the liquid to be separated drop by drop near the boundary between two layers.

It is used to separate immisicible liquid mixtures with different densities such as oil and water.

Distillation column/Fractionating column

A distillation column is a usually a glass column that provides a large surface area for continuous condensation (reflux) and re-boiling to occur so as to separate one liquid component from another. It is used for separating a liquid from a simple solid-liquid mixture or from a complex mixtures of several miscible liquids such as liquefied air and crude oil. The greater the surface area, the more efficient the separation will be. The surface area can be increased by adding glass beads, glass plates or sieves.

Displacement can/Eureka can

The displacement is a large container with a spout that is usually used to find the volume of impermeable irregular solids. Water is filled up to the spout and the solid to be measured is lowered gently into the can to prevent splashing. Water is then displaced by the solid. The solid used must have a higher density than water so that it can submerge below the water surface for accurate measurement of volume. A measuring cylinder is usually used to collected the water displaced.

Magnet

A magnet is used in chemistry to separate magnetic substances from non-magnetic ones. Magnetic substances are made of iron, steel, nickel or cobalt.

Voltmeter, ammeter

Voltmeters and ammeters are used very frequently in Physics experiments. Voltmeters are used to measure potential differences (p.d) or voltage while ammeters are used to measure electric current. They are mentioned here because there is also a topic in the Chemistry that involves electricity known as electrochemistry.

Digital Multimeter

A multimeter is able to measure both current and potential difference. It can be used in place of a voltmeter and ammeter. Being digital, it it also able to record more decimal places and is therefore higher in accuracy.

Stopwatch

There are both analogue/mechanical and digital stopwatches. Analogue/mechanical stopwatches have an accuracy of 0.1-0.2s. Digital stopwatches are more accurate and have a accuracy = 0.01s, hence they are used in most school laboratories.

Human reaction time
As the stopwatches are operated manually, an error called human reaction time error always occur. There is delay between you observing something and pressing the start or stop button on the stopwatch. This is about 0.2s (or 200ms). For example, in measuring the duration of a chemical reaction, a person may not always start or stop the stopwatch at exactly the same point every time. The person can sometimes be starting or stopping the stopwatch earlier, later or at the exact point of time. The results in random errors and can be reduced by repeating the experiment several times. Another way is to use sensors to start and stop the timer automatically without the intervention of humans.

pH indicator, pH meter

The pH measures the relative concentration of hydrogen ions, H⁺, in a solution. A pH indicator is a dye or a mixture of dyes that change colour when the pH changes. In most laboratories, there are Universal indicator solution and Universal indicator paper to measure a range of pH values from 0 to 14 (the pH scale) and they are able to produce a range of rainbow colours for individual pH values.

There are also pH indicators that show only 2-3 colour changes such as the blue and red limus paper, methyl orange and phenolphthalein.

The blue and red litmus paper are useful to test whether a substance is acidic or alkaline but is unable to show how acidic or alkaline a substance. They are also used to test for acidic gases such as chlorine, hydrogen chloride and nitrogen dioxide and alkaline gas such as ammonia.

Methyl orange and phenolphthalein are commonly used to indicate the end-point of an acid-base titration experiment.

You will learn more about pH indicators and pH meters when studying acids and bases.

Common reagents

Some chemicals are usually prepared in advance to help you speed up your analysis in the laboratory. Some of these include:

dilute hydrochloric acid [HCl(aq)]
dilute sulfuric acid [H₂SO₄(aq)]
dilute nitric acid [HNO₃(aq)]
dilute phosphoric(V) acid [H₃PO₄(aq)]
dilute sodium hydroxide [NaOH(aq)]
dilute potassium hydroxide [KOH(aq)]
aqueous ammonia [NH₃(aq)]
silver nitrate solution [AgNO₃(aq)]
barium nitrate solution [Ba(NO₃)₂(aq)]
lead(II) nitrate solution [Pb(NO₃)₂(aq)]
iodine solution/aqueous iodine [I₂(aq)]
aqueous potassium manganate(VII) [also known as potassium permanganate, KMnO₄(aq)]
aqueous potassium dichromate(VI) [K₂Cr₂O₇(aq)]
aqueous potassium iodide [KI(aq)]

Photographs of apparatus and their laboratory diagrams:

Guidelines for lab diagrams:

The lines should be clear-cut, therefore using a pencil and ruler to draw straight lines are recommended.
There should be minimum or no shading. For those that required shading such as a stopper, using diagonal lines instead of artistic shading.

Apparatus	Photograph	Lab diagram	Purpose
Safety goggles		-	To protect he eyes from irritation and chemical spashing
Test tube			To mix or heat small amount of solids and liquids
Test tube rack		-	To hold test tubes in place
Test tube holder		-	To hold a test tube for heating
Test tube brush		-	To wash the insides of test tubes.
Boiling tube	Slightly bigger than a test tube	Slightly bigger than a test tube	To mix or heat small amount of solids and liquids
Funnel			To hold a piece of filter paper for filtration or avoid spilling and splashing when transferring liquids between containers
Filter paper			To collect insoluble solid residue from filtration and to separate complex solid mixtures such as dyes and amino acids during paper chromatography
Spatula			To transfer small amounts of solids in the form of powder or granules
Stirring rod			To stir mixtures, transfer a drop of solutions, test for solutions saturation and scrape crystals off during crystallisation
Double beam balance	-	-	Measure mass
Triple beam balance		-	Measure mass
Electronic balance			Measure mass accurately Accuracy = 0.01g
Wash bottle			Contain distilled water for washing residues or containers
Beaker			To hold solids or liquids. It is not usually used for accurate measurement.
Measuring cylinder			Measure liquid volume to an accuracy of 1ml or 1cm³
Burette			Measures liquid volume accurately to an accuracy of the nearest 0.05cm^{3. M}ures liquid
Pipette			Measure a fixed volume of liquid accurately, eg 25.0cm3, 50.0cm3
Pipette filler		-	Used with a pipette to suck up and release liquid
Dropper/ Teat pipette			To transfer liquid by drops
Conical flask/ Erlenmeyer flask			To contain liquid mixtures. The narrow neck and wide base are suitable for swirling. The narrow neck helps to reduce splashing and evaporation.
Round-bottomed flask			To contain liquid for heating. The round bottom helps to distribute heat evenly
Volumetric flask			To make standard and diluted solutions
Evaporating dish			For heating to evaporate water from mixtures
Watch glass			To hold small amounts of solids or cover a beaker or evaporating dish
Crucible and lid			To heat heat-stable solid. The lid can be used to contain smoke particles.
Crucible tongs		-	To move a heated crucible around
Bunsen burner			Provides a strong heat source for heating substances
Tripod stand			Provide a support for beakers, tubes and flasks to rest while being heated with a Bunsen burner
Wire gauze			Provide a surface for beakers, tubes and flasks to rest while being heated with a Bunsen burner and to distribute heat evenly
Clay triangle			Hold a crucible on a tripod stand or ring stand while it is being heated by a Bunsen burner.
Retort stand			A variety of clamps can be attached to retort stands to hold different apparatus.
Burette clamp		See retort stand above. All clamps can be generalised as the diagram above	Attach a burette to a retort stand
Universal clamp		See retort stand above.	Attach test tubes and flasks to a retort stand
Hot plate			Used as sources of heat when Bunsen burner flame is not desirable, such as heating a volatile liquid.
Water bath		See water trough below and label the diagram as a water bath.	Maintain water at a constant temperature
Condenser			Collect and condense vapour into liquid efficiently by providing a cool elongated inner surface through the flow of a cooling liquid.
Delivery tube			Transfer gas between 2 containers
U-tube			Transfer gas between 2 containers. Usually used with a drying agent so that moist air that enters will exit the tube as dry gas.
Water trough			Contain water for collecting gases or acting as a water bath
Gas jar			Collect and store gases
Beehive shelf			Support a gas jar while collecting a gas from a reaction mixture
Thistle funnel			Transfer small amounts of liquid to an existing mixture
Rubber stopper			Prevent gas from entering or escaping a tube or flask. Transfer gas between containers by allowing the use of a delivery tube.
Gas syringe			To collect and measure the volume of gas
Mercury-in-glass thermometer			Measure temperature
Alcohol-in-glass thermometer		Same as mercury-in-glass thermometer	Same as mercury-in-glass thermometer
Separating funnel			Separate immiscible liquid mixtures
Fractionating column			Provide a large surface area for continuous condensing and re-boiling during distillation for efficient separation of miscible liquid mixture
Displacement can			Contain water and use the displacement of water method to measure the volume of an impermeable irregular solid
Magnet			For magnetic separation of mixtures
Voltmeter			Measure the potential difference between 2 points in an electric circuit
Ammeter			Measure current
Digital Multimeter		-	Measure both current and potential difference
Analogue stopwatch		-	Measure time to an accuracy of 0.1-0.2s
Digital stopwatch			Measure time to an accuracy of 0.01s

Some experiment setups:

Physical Quantities
A physical quantity is a property of a substance or material that can be observed and measured. It consists of a numerical value that indicates its magnitude and a unit.

There are 7 base physical quantities. All other quantities can be derived from the base quantities and are called derived quantities. Each base quantity has a base SI unit. SI refers to the International System of Units, from French Système international d'unités.

Base quantity, Symbol	Base SI unit, Symbol
Mass, m	kilogram, kg	Used frequently in Chemistry
Length, l	metre, m	Used more frequently in Physics
Time, t	second, s	Used frequently in Chemistry
Thermodynamic temperature, T or θ	kelvin, K	Used frequently in Chemistry
Electric current, I	ampere, A	Used more frequently in Physics
Amount of substance, n	mole, mol	Used frequently in Chemistry
Luminous intensity, l_v	candela, cd

Derived quantity, Symbol	Derived SI unit, Symbol
Volume, V	cubic metre, m³
Velocity, v	metre per second, m/s or ms^-1
Acceleration, a	metre per squared second or metre per second per second, ms² or ms^-2
Density, p	kilogram per cubic metre, kg/m³ or kgm^-3

Measuring mass

Apparatus	Accuracy	Remarks
Beam balance	1g	Slow to use
Electronic balance	0.01g	Fast to use

Mass is the amount of substance in a body.
Mass is one of the 7 base physical quantities.
The SI unit for mass is kilogram, kg. This is the only SI unit with a prefix (kilo-).
Other units are gram (g), milligram (mg), and tonne (ton).
1 kg = 1000 g (10³ g)
1 ton = 1000 kg (10³ kg) = 1000000 g (10⁶ g)
An electronic balance is more accurate and faster to use.

Measuring volume

Volume is the amount of space taken by a body.
Volume is not one of the 7 base physical quantities. It is a derived quantity from 3 measures of length.
The SI unit for volume is the cubic metre, m³.
Other units are cubic centimetre (cm³), cubic decimetre (dm³).
Litre (l) and millilitre (ml) are used for liquid volumes as well.
1 m³ = 100 cm x 100 cm x 100 cm = 1000000 cm³
1 dm³ = 1000 cm³
1 l = 1000 ml = 1000 cm³
1 l = 1 dm³ = 1000 cm³
1 cm³ = 1ml
In chemistry, you will most frequently be involved in measuring the volume of liquids and gases.

Liquid volume
The accuracy below refers to the smallest interval etched on the tube.

Apparatus	Size	Accuracy	Record up to
Measuring cylinder	various size, some as small as 10cm³	1cm³	1cm³ e.g. 2cm³
Burette	usually 50.00cm³	0.1cm³	0.05cm³ (you have to estimate this) e.g. 24.15cm³, 22.10cm³
Pipette	usually 25.0cm³	0.1cm³	25.0cm³

Comparing the accuracy of beakers, measuring cylinders, burettes and pipettes
Least accurate <----- -----> Most accurate
beaker < measuring cylinder < burette < pipette

Differences between a measuring cylinder and a burette

Measuring Cylinder	Burette
0cm³ starts from the bottom	0cm³ starts from the top
Accuracy = 1cm³	Accuracy = 0.1cm³
Record up to 1cm³	Record up to the nearest 0.05cm³
No tapering lower end	Has a tapering lower end, sometimes with rubber tubing and clip
Pour liquid in and record the volume	Fill up burette, release a specific volume of liquid before and record the derived volume

Meniscus
A meniscus is the curved upper surface of a liquid in a tube caused by surface tension. You will see meniscus most prominently in narrow tubes such as measuring cylinders, burettes and pipettes.

A meniscus can curve downwards or upwards, depending on the type of liquid

When the meniscus curves downwards, read the bottom of the meniscus. For example, water.
When the meniscus curves upwards, read the top of the meniscus. For example, mercury.

Note: Mercury is the only metal that exists as a liquid at room temperature and pressure.

Gas volume
Gas volumes are best measured using a gas syringe. Accuracy can range from 0.01 cm³ to 1 cm³.

Steps in using a gas syringe
1. Push the plunger into the gas syringe until all air is expelled.
2. Connect the gas syringe to one end of a delivery tube.
3. Attach the other end of the delivery tube to the reaction container that will produce a gas. Ensure there is a rubber stopper to prevent the gas from escaping and to ensure the delivery tube is fixed securely at the opening.

Measuring time

	Accuracy
Analogue/Mechanical stopwatch	0.1s or 0.2s
Digital stopwatch	0.01s

Time is one of the 7 base physical quantities.
The SI unit for time is seconds, s.
Other units include minute (min), hour (h), millisecond (ms), and nanosecond ns).
The digital stopwatch is more accurate than the analogue stopwatch.
There are errors due to human reaction time.

Human Reaction Time
Due to human reaction time, there will be some randoms involved in the measurement of time. To reduce the error, you can repeat an experiment a few times and calculate the average time taken.

Measuring temperature

Temperature is one of the 7 base physical quantities.
The SI unit for temperature is kelvin, K.
The unit, kelvin (K), is related to the thermodynamic absolute temperature scale. 0 K is known as absolute zero and is the lowest theoretical temperature that any substance can become. At this temperature, it is said that all particles in the substance will stop vibrating.
Other units used are degree Celsius (C) and degree Fahrenheit (F).
Converting between the kelvin and Celsius scales: K = °C + 273 K
1 K = 1 °C
The melting point of ice is 0 °C (0 + 273 =273 K).
The boiling point of pure water at normal atmospheric pressure is 100 °C (100 + 273 = 373 K).
Room temperature is 25 °C (25 + 273 = 298 K)
Converting between the Celsius and Fahrenheit scales: °F = 9/5 x °C
Since 9/5 is close to 2.0, °F is about twice the value of °C.
1 K = 1.8 °F
A data logger can also be used with a temperature sensor to measure temperatures at regular time intervals for observing trends over a period of time.

Temperature	°C	K
Melting point of ice	0	273
Room temperature	25	298
Boiling point of pure water at normal atmospheric pressure	100	373

Measuring current and potential difference (voltage)

Current is one of the 7 base physical quantities.
An ammeter is used for measuring the amount of electric current.
The SI unit for current is the ampere, A.
Potential difference or voltage is not a base quantity as it can be derived from other base quantities.
A voltmeter is used for measuring the potential difference between two points in an electric circuit.
The SI unit for potential difference is the volt, V.
Both meters can be connected between an anode and a cathode in a simple electric cell to measure the amount of electric current or voltage produced.

Deriving density

Density is the mass per unit volume of a substance.
It is not a base quantity but a quantity can be derived from the base quantity of mass and the derived quantity of volume which in turn is derived from the base quantity of length.

Therefore, the unit for density is derived from the units of mass and volume.
In SI units, kg/m³ or kgm^-3
Another common unit is g/cm³ or gcm^-3.
You will also need to know how to convert between kg/m³ and g/cm³
1 g/cm³ = 1000 kg/m³. See the working below.
Hence, to convert from g/cm³ and kg/m³, multiply by 1000
Example: The density of water is about 1 g/cm³ = 1 x 1000 = 1000 kg/m³
And, to convert from kg/m³ to g/cm³, divide by 1000
Example: The density of gold is 19320 kg/m³ =19320 / 1000 = 19.320 g/cm³

Collecting and Drying Gases

Many times, gases are mixed with water vapour. To obtain a pure and dry sample of gas, you will need to remove the moisture using drying agents. You will learn more about the collection and drying of gases in the topic on physical separation methods.

How gases are collected and dried depend on their properties, their pH, solubilities in water, and their densities (using relative molecular mass) compared to air. Air is predominantly made up of nitrogen gas, so the average relative molecular mass is about 28-29). You will see more details in the topic on physical separation methods. Here, the focus is on the apparatus used.

Gas	pH	Solubility in water	Relative molecular mass	Density
hydrogen gas, H₂	neutral	insoluble	2	lighter than air
oxygen gas, O₂	neutral	slightly soluble	32	slightly heavier than air, downward delivery is not effective
carbon dioxide, CO₂	acidic	slightly soluble	44	heavier than air
chlorine, Cl₂	acidic	soluble	71	heavier than air
hydrogen chloride, HCl	acidic	very soluble	36.5	heavier than air
sulfur dioxide, SO₂	acidic	very soluble	64	heavier than air
ammonia, NH₃	alkaline	extremely soluble	15	lighter than air

3 Drying agents	Remarks
concentrated sulfuric acid [conc. H₂SO₄(l)]	Cannot be used to dry alkaline gases, such as NH₃
calcium oxide [quicklime, CaO(s)]	Cannot be used to dry acidic gases such as HCl
fused calcium chloride [CaCl₂(s)]	Can be used for most gases except NH₃ as they will react to form an additional compound

Note: (l) means liquid state and (s) means solid state. Fused means the calcium chloride has been heated to remove moisture from it.

Apparatus for different drying agent and gas
(Source: minichemistry.com)

Concentrated sulfuric acid
Notice that the two delivery tubes used are positioned differently. The incoming gas has to be bubbled into the acid. The other delivery tube is not dipped into the acid. Otherwise, if the tube comes into contact with the acid, it will be wet and will not be able to deliver dry gas.

Calcium oxide
Below shows the use of a vertical column with delivery tubes and rubber stoppers and allowing the ammonia gas to move upwards. This is known as upward delivery.

Fused calcium chloride
Below shows a U-tube used with delivery tubes and rubber stoppers.

Apparatus for collecting gases

Upward delivery
For gases less dense than air, the upward delivery (downward displacement of air) is used. This is for hydrogen (H₂) and ammonia (NH₃). The apparatus involved are delivery tube and gas jar.

Downward delivery
For gases denser than air, the downward delivery (upward displacement of air) is used. This is for carbon dioxide (CO₂), chlorine (Cl₂), hydrogen chloride (HCl) and sulfur dioxide (SO₂). This method is not effective for oxygen (O₂) which is only slightly denser than air. The apparatus involved are delivery tube and gas jar.

Water displacement
For gases that are insoluble or only slightly soluble in water, the water displacement can be used. This is for oxygen (O₂), hydrogen (H₂) and carbon dioxide (CO₂). The apparatus may involve a gas jar, beehive shelf, delivery tube and a water trough.

Gas syringe method/system
The gas syringe method or system is the most versatile. It can be used to collect any gas. It also can measure the volume of gas formed. A delivery tube can be attached to the tip of the gas syringe to transfer gas into it.

Safety rules in the laboratory

Do not eat and drink in the laboratory.
Do not inhale or taste any chemicals.
Follow the instructions of your teacher or lab technician.
Wear safety gear such as safety goggles at all times.
Dispose leftover and waste chemicals properly.
In case of chemical spillage on your skin, wash with plenty of tap water and inform the teacher immediately.
Do not bring any chemicals out from the laboratory.
Know where the safety equipment (such as fume chamber) are and when to use them.
Do not work alone in the lab.
Keep flammable substances away from the Bunsen burner.
Keep long hair tied up neatly.
Do not wear sandals and other open-toed footwear. Always wear shoes that cover the entire foot.

Hazard Symbols
In the laboratory, you may observe the following hazard symbols on chemical bottles or certain equipment. Due to new regulations in Europe, new hazard symbols from the Globally Harmonized System of Classification and Labelling (GHS) have replaced the old orange "chip" symbols since 2017 in Europe. Other countries are gradually following suit.

The radiation and biohazard symbols are not part of the GHS system but are from other international standard.

Hazard	Old Hazard Symbol	New Hazard Symbol	Description	Examples
Explosive			Very reactive substances that produce gas at dangerously high temperature and pressure	TNT (trinitrotoluene), pyrotechnic mixtures
Flammable			Substances that burn easily	Ethanol, propane, butane, hydrogen
Oxidising			Substances that provide oxygen and cause other substances to combust/burn	Oxygen, hydrogen peroxide, potassium nitrate, nitric acid, potassium permanganate
Toxic			Substances that are poisonous or fatal if inhaled, ingested or absorbed through the skin	Methanol, ammonia, formaldehyde, nicotine, carbon monoxide
Harmful Irritating			Substances that can irritate the skin, eyes and respiratory tract. They can cause reddening, swelling and pain.	Naphtha, butane, ethanol, chlorine
Corrosive			Substances that corrode metals, burn the skin and cause eye damage	Sulfuric acid, nitric acid, sodium hydroxide, ammonia
Dangerous for the environment			Substances that are toxic to aquatic systems	Sulfuric acid, turpentine, lead, mercury, crude oil
Health hazard	-		Substances that pose a health hazard to humans, causing skin irritation or corrosion, serious eye damage, respiratory damage, cell mutation, cancer and organ poisoning	Carcinogens such as benzene, arsenic and asbestos.
Gases under pressure	-		Gases that are stored under high pressured in gaseous state, liquid state and dissolved state	Compressed oxygen, helium and nitrogen; liquefied carbon dioxide; dissolved acetylene
Others: Radioactive		-	Substances that decay naturally and give off particles that can penetrate matter	X-ray machine, radioisotopes such as uranium-235, iodine-231, caesium-134, caesium-137
Others: Biohazardous		-	Substances are infectious and are biological in nature	Blood samples, body fluids, body tissues, microbiological wastes, animal waste

These are the equivalent ISO 7010 symbols for the above list. ISO stands for International Standards Organization.

Explosive	Flammable	Oxidising	Toxic

Pressurised Cylinder	Corrosive	Radioactive	Biohazardous

The Scientific Method

Scientific Attitudes

Hypothesis

A hypothesis has to be tested.

Independent variable

Dependent variable

Constant variable

Conjecture

Theory

Law

Resources to read more about
A good webpage to read about hypothesis, conjecture, theory, law and principle

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TMSI Math & Science Study Notes

Monday, January 27, 2020

Experimental Chemistry