Chemistry Form One Notes – Heat Sources and Flames
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Heat sources
Different Heat Sources which can be Used in a Chemistry Laboratory
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A candle can only be used where a chemical reaction does not require much heat. Its
disadvantage is that it produces lot of soot. The ater burers, though not commonly used, are
The eectic heater uses electricity, The gus bumer uss a iqueted gas. The disadvantage of an
electric burer is that it cannot be wed in rural areas whee there sno electricity
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Candle
A kerosene burner
A kerosene burner (stove), also called ito fa china in Swahili, if well adjusted can produce a
flame ht enough to heat many substances inthe laboratory. tis flld with kerosene, a fel ha
affordable
It can conveniently be used by schools inthe most emote areas were there is no electricity, If
too much beating is required, wite gauze should be placed on top ofthe bumer. This will enable
reduce soot and increase the eating temperatures to about 1000°C or more
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However, the heat produces is not hot enough to init some reactions
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‘The Functioning of a Bunsen Burner
OF ll the burmers we have discussed so far, a Bunsen burner isthe mostly used. Therefore, we
are pong to discuss about the functioning ofthe Bunsen burner in more detail, As the name
suggests, this bumer waa invented by German scientist called Robert Bunsen, soit was ramed
after his name as a Bunsen burner. The burner uses coal ess, which burs with a hot and non-
luminous flame when the air holes are open. Ths is a kind of flame we normally use inthe
laboratory
Functions of different parts of the Bunsen burner
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Base: Supports the mer. I makes the burer stable, de its heavy weight, when placed on
bench
Gas inet: Lets the gas in from the gas supply
Jet Directs the gas tothe barrel
Collar: Regulates the amount of ar entering the burner. It has ar holes that ean be turned open
cor closed depending on the kind of flame, and hence amount of heating required.
[Air holes: These small hols on the collar allow iro enter i the burner.
Barrels This isa part ofthe burner where air (from outside), and gas (fom gas supply) mix up
and bum
How to light a Bunsen burner
Aer knowing the differen pars ofthe Bunsen burner, tis important that you also learn how to
light it. This is because careless use ofthe bumer may lead to acident or wastage ofthe gas. The
following sa comect sequence of steps on how to light the Bunsen burner
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5. Tum the collar to adjust the ar holes until you get the type of lame you want, You may
have the holes completly open,
To put off the flame of the burner aftr you Finish heating a substance, tum the gas tap off in
cde to ut off the gas supply to the bumer. Disconnect the burner from the gas mins by
removing the rubber tube connecting the two. Then close the air oles. Pay attention not to touch
the hot collar with your fingers or else wait until itis cool enough. Take the Bunsen burner and
keep it atthe appropiate place
Types of flame
Flames are formed by buming gases or vapours. During buming, heat and light are given out
For any solid or iquid to bum with a lame, it must ist turn into inflammable vapours (gaseous
state).
Luminous and Non-luminous Flames from Different Types of Flames
Produce luminous and non-uminous flames from diffrem types of flames
‘A fame canbe luminous or nor-luminous, Flames ofa candle and any clare usually smoky and
Juminous. Flames of such kind are normaly of litle laboratory use. This is because they ate not
tot enough and would deposit sot on laboratory apparatus. Cal gas also burns witha smoky
and luminous flame, With a Bunsen burr, one can produce two types of flames namely, the
Juminous and non-tuminous Names.
Luminous flame
This is type of flame produced when the air holes of « Bunsen burner are closed, When the air
hols are closed very litle air enters the barrel ofthe burner. In this ase, the lame willbe large
unsteady and bright
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Non-luminous flame
When air holes are flly opened, sufficient air enters the Bunsen bumer bare and mixes well
withthe coal gas. Hence, the buning ofthe gas is much quicker and complete. The flame is
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Major differences between luminous and non-luminous flames
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Investigation of different parts of a flame
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The unburnt ga canbe shown to have risen up the tube By puting a ight athe top ofthe tube
‘The fame wil form, This indicates the escape of unburt gas through the tbe
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Toindcae the presence ofunbur gas in a Bunsen burner flame
Uses of flames
Flames are wed for diferent purposes, Some wes ofthe fame incde the following:
flame, which produces rich heat, is used. However, for reactions that require litle hea,
luminous fame, which is not very hot, canbe used
Preliminary tests normally used to identify an element. When some elements ae strongly heated,
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they produce characteristic flame colours that distinguish them from one another. A non:
luminous flame is often used
+ Production of light. Flames produce light that can be used to light a dark room.
Therefore, an experiment that involves heating can even be conducted in the dark. The same
flame is used to give heat as well as light, Here, a luminous flame is used. Examples of heat
sources, which produce flames that may be used for lighting, are hurricane lamp, tin lamp, spirit
lamp and candle
+ Cooking: Since it gives a hot flame and produces no soot, a non-luminous flame ean be
used for cooking food. Gas cookers, gas stoves and kerosene stoves usually produce such flames.
+ Welding: A. non-luminous flame is suitable for welding because it is very hot. In most
welding operations an oxyacetylene gas, a mixture of oxygen and ethyne, is sed. When burned,
the gas produces aflame hot enough to cut or melt the metal
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