Does a left on kettle still burn power and if so how much?

[raleighnut]

No it's that ground stuff you're supposed to put in one of these. View attachment 356945

I haven't got one of those,so i just pour boiling water on the stuff,leave it till the bits settle,then stir it again and add milk. You do get the occasional floater,but it's not that bad. Someone who came to visit the other day left the brew i'd made for them.,saying "Oh,it has bits floating on top" I said to them,imagine you're in the trenches the night before the Battle of the Somme and that was in front of you. You wouldn't be worried about little bits of coffee floating on top then would you?!

View: https://youtu.be/XSg2cq5xx2Y

 

[smutchin]

• high pressure today, so boiling point might actually be at 100 celcius. Apparently it's usually 99.6

Will the boiling point be affected by the pressure inside the kettle? I know the kettle isn't a pressure cooker, but it is an enclosed space, and my limited physics tells me that's one of the reasons it boils quicker than water in a saucepan with the lid off. I guess it might also be affected by how full the kettle is?

My kettle never reaches 100ºC before it switches itself off - I just tested it with my Thermapen (claimed accuracy of ±0.4ºC) and immediately after it clicked off, the temperature was 98.3ºC. I've always assumed that was to do with the thermostat, but maybe there are other factors.

90 degrees would probably be about right for coffee

For real coffee, received wisdom* is that 96ºC is the correct temperature. For instant coffee, there's probably no point heating it up more than just short of being too hot to drink, which at a guess is about 65ºC.

*according to countless online poncey hipster coffee-making guides.

 

[smutchin]

Let's just head to Accy's for a brew. It's the only way to be sure.

Having just read how he makes coffee... no, thanks.

 

[Accy cyclist]

Having just read how he makes coffee... no, thanks.

You'd like it,it just takes a bit of getting used to.

 

[smutchin]

You'd like it,it just takes a bit of getting used to.

I tried that line on my girlfriend once...

 

[glasgowcyclist]

I've always emptied the unwanted boiled water down the sink,as i think it's useful for getting rid of any grease lurking down the plughole. I'm going to try and get out the habit and keep the water in the kettle. I remember my dad who was supposed to be a stickler for saving money, had a bad habit of filling and boiling a kettle just to make one cup of tea or coffee. Then he'd just leave the remaining water(about 1 litre) to cool off. That was a waste to me,so that's why i developed the waste not want not,pour it down the sink to get rid of grease etc habit. Though i never fill the kettle to the top like he did. I always try to judge the right amount. When i say i pour the unwanted water down the sink,it only amounts to about half a cup.

Nooooo!

For a guy who's worried about 50p worth of electricity you're not very thrifty. Your idea of degreasing your plug 'ole is pointless. Better to keep a thermos flask beside the kettle and tip any unused water into that for later use. It'll take much less energy to get back to boiling and you won't be wasting water.

 

[marinyork]

Will the boiling point be affected by the pressure inside the kettle? I know the kettle isn't a pressure cooker, but it is an enclosed space, and my limited physics tells me that's one of the reasons it boils quicker than water in a saucepan with the lid off. I guess it might also be affected by how full the kettle is?

You're talking over two minutes to heat the water and this is a relatively small change vs a phase change where large(r) amounts of a fluid are kicked out each second. If we went on a ludicrous assumption of it being a totally closed system.

P_1 x V_1 / 283 K = P_2 x V_2 / 373 K. Assume V is constant (this is a ridiculous assumption as air is forced out of the spout slowly over a couple of minutes). V's cancel.

So P_2 = 373/283 * P_1. So pressure would increase by about a third.

Pressure increasing by a third would mean the boiling point of water would be about 107 degrees Celcius. Of course the assumptions are not realistic as air is forced out of the kettle slowly for a couple of minutes and then water vapour is forced out of the spout very rapidly in comparison when a phase change happens. The water vapour being forced out won't be clean there will be vortices.

 

[smutchin]

Pressure increasing by a third would mean the boiling point of water would be about 107 degrees Celcius.

Ah. I was confusing myself by thinking that higher pressure would reduce the boiling point. I can see that's nonsense, of course.

Obviously the quicker boiling time for a kettle vs an open pan is to do with conservation of energy rather than pressure, right?

 

[marinyork]

Ah. I was confusing myself by thinking that higher pressure would reduce the boiling point. I can see that's nonsense, of course.

Obviously the quicker boiling time for a kettle vs an open pan is to do with conservation of energy rather than pressure, right?

Higher pressure does mean that the boiling point will be higher, but it's not linear (where the 107 came from).

It's one of those things at school where the syllabus where on GCSE/A-level chemistry they don't explain what the smeg it means and a lot of people who even remember it are thinking triple point of water being 0.01 degrees C isn't that a bit daft, can't we stick to 0.00 C and just call that the melting point instead.

 

[swee'pea99]

The kettle is now at the other side of the kitchen,about 5 yards away from the base. i think it's safer over there!

I think to be on the safe side you really need to be thinking in terms of the end of the garden. Or perhaps you could have a neighbour look after it when you're not using it.

 

[classic33]

Nooooo!

For a guy who's worried about 50p worth of electricity you're not very thrifty. Your idea of degreasing your plug 'ole is pointless. Better to keep a thermos flask beside the kettle and tip any unused water into that for later use. It'll take much less energy to get back to boiling and you won't be wasting water.

You're reairiating the water doing that.

 

[classic33]

Higher pressure does mean that the boiling point will be higher, but it's not linear (where the 107 came from).

It's one of those things at school where the syllabus where on GCSE/A-level chemistry they don't explain what the smeg it means and a lot of people who even remember it are thinking triple point of water being 0.01 degrees C isn't that a bit daft, can't we stick to 0.00 C and just call that the melting point instead.

View attachment 356956

Why do we get ice when it's above 0.00°C though.

 

[classic33]

Is that where the ice itself is above 0.00°c?

I'll let you know the next time it gets cold enough.
Water can exist in liquid form, well below 0.00°C.

 

[lazybloke]

My Kelly kettle has no moving parts (v reliable) and holds only a finite fuel source, so no need for safety cut off mechanisms.
Fun too. Fire innit?

Edited to add random youtube video. Got to love that mini blast-furnace action!

 

[ColinJ]

Water can exist in liquid form, well below 0.00°C.

It is quite interesting to put a (plastic!) bottle of sparkling mineral water in a freezer for a while and chill it down to below freezing point, but take it out before it actually freezes solid. If you get it right, you can pour it out into a glass and have it freeze as soon as it gets there. In theory, you could get it to freeze in mid-air but I haven't managed that yet.

(I discovered that by accident. My tipple these non-alcohol days is sparkling mineral water with OJ. Sometimes I try to chill the water in a hurry and leave it in the freezer a bit too long.)