insulation shield for alcohol burning experiment (1 Viewer)

[indeed]

I've got an experiment (graded) about enthalpy of combustion measured through burning different alcohols (methanol, ethanol etc.) in spirit burners. One thing that was emphasised was using a heat insulating shield covering three sides of the experiment (to prevent heat loss).

I know that this comes at the cost of oxygen lost but I think it'll be better to do it for 'shows' sake, does anyone have any tips on what materials to use to make the shield? (I was thinking polystyrene but it's flammable, so was thinking of aluminium foil wrapped around polystyrene)

 

[nsw..wollongong]

r u talking abt heating under reflux?

 

[carrotsss]

r u talking abt heating under reflux?

No, when you’re measuring heat of combustion from a spirit burner you need to trap the heat or else the results will be way off

I think we used some combination of polystyrene and aluminium but I don’t really remember

 

[indeed]

Oh ok, yh that's what i was thinking but want to avoid a fire as well

 

[nsw..wollongong]

No, when you’re measuring heat of combustion from a spirit burner you need to trap the heat or else the results will be way off

I think we used some combination of polystyrene and aluminium but I don’t really remember

ohhh my bad

 

[Eagle Mum]

Google ‘large ceramic incense burner with lid’. Ceramic is a reasonably good insulator - that’s why we use it for hot beverages.

 

[Eagle Mum]

Actually, most basic ceramic teapots would probably provide adequate insulation.
Try K-Mart, Big W, Target, IKEA or a kitchen warehouse.

 

[Eagle Mum]

Might be worth pouring boiling water into a food thermos container and into a ceramic container (teapot or soup mug) and see which has held the temperature of the water better after five minutes.

 

[indeed]

Oh ok thank you for advice

I think ceramics might be a bit difficult to use, and expensive, as I would need a really large ceramic box, thanks anyways

 

[wizzkids]

Calculating the Molar Enthalpy of Combustion of a variety of fuels is a classic first-hand investigation in Chemistry.
It usually goes for about five minutes or until a reasonable mass of the fuel has been combusted, so that students can accurately calculate the moles of fuel that has been combusted.
I'm sorry to say it will be very difficult to install an insulating shield around your experiment that improves the accuracy of the experiment.
Firstly let's identify the ways that heat could be lost from the system.
They are by

• conduction,
• convection and
• radiation.

Think about practical ways that you can keep the heat in the calorimeter and limit the heat losses by conduction, convection and by radiation.
This investigation involves heat transfer by convection from a hot burning gas to a metal calorimeter containing a thermometer.
Anything that stops wind gusts from blowing the flame is potentially useful and you should do it.
Here are some other examples of heat losses:
(1) Heat conduction into the clamp that is holding your calorimeter.
(2) Heat convection by hot gases rising past the vessel and into the room.
(3) Heat radiation from the vessel to the room.
Of these, (2) represents the overwhelming bulk of the heat losses from the system, and there is not much you can do to limit that heat loss in a simple experiment.
(3) will be improved by an insulating shield, but it would need to be made of a shiny material that reflects 100% of the incident radiation. However, there is a fundamental problem with reflection - you can't send 100% of reflected waves back towards the calorimeter. It reflects at all possible directions, and only a small percentage will be reflected back at the calorimeter, so it is of doubtful value.

 

[indeed]

Calculating the Molar Enthalpy of Combustion of a variety of fuels is a classic first-hand investigation in Chemistry.
It usually goes for about five minutes or until a reasonable mass of the fuel has been combusted, so that students can accurately calculate the moles of fuel that has been combusted.
I'm sorry to say it will be very difficult to install an insulating shield around your experiment that improves the accuracy of the experiment.
Firstly let's identify the ways that heat could be lost from the system.
They are by

• conduction,
• convection and
• radiation.

Think about practical ways that you can keep the heat in the calorimeter and limit the heat losses by conduction, convection and by radiation.
This investigation involves heat transfer by convection from a hot burning gas to a metal calorimeter containing a thermometer.
Anything that stops wind gusts from blowing the flame is potentially useful and you should do it.
Here are some other examples of heat losses:
(1) Heat conduction into the clamp that is holding your calorimeter.
(2) Heat convection by hot gases rising past the vessel and into the room.
(3) Heat radiation from the vessel to the room.
Of these, (2) represents the overwhelming bulk of the heat losses from the system, and there is not much you can do to limit that heat loss in a simple experiment.
(3) will be improved by an insulating shield, but it would need to be made of a shiny material that reflects 100% of the incident radiation. However, there is a fundamental problem with reflection - you can't send 100% of reflected waves back towards the calorimeter. It reflects at all possible directions, and only a small percentage will be reflected back at the calorimeter, so it is of doubtful value.

Yeah that's true, I might just attempt to make an insulator to reflect heat radiation, though it will probably barely change the actual enthalpy of combustion, I'll do it for marks' sake. Thank you for accuracy tips though!