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thermal insulator - please help

Discussion in 'Science' started by taspat, Jan 3, 2011.

  1. Hi, Im a Primary PGCE student and I'm going to be teaching year 4 the qca module keeping warm. I desperately need some advice. The first lesson I'm going to teach is on how to keep the snowman from melting (using ice) - so keeping cold and the second will be how to keep the bottle of water warm for my tea (using hot tap water) - so keeping warm.
    I'm worried that I have not fully understood the science behind it and I don't want to explain it incorrectly to the children. I understand that the thermal insulator keeps cold things cold and warm things warm and I understand that this term will need to be used in both lessons. However, what is the difference between the term insulator and thermal insulator and am I right to use thermal insulator with the children?
    I read in a science subject knowledge book (there's not much on this topic in there) that the thermal insulator prevents transfer of heat between objects. Now if i explain this to the children they will probably say that the ice is cold so how can it give out heat. I have no idea how I would respond to this, probably because I don't think I understand this myself! Could anybody please help me understand this?
    Thank you in advance

     
  2. Hi, Im a Primary PGCE student and I'm going to be teaching year 4 the qca module keeping warm. I desperately need some advice. The first lesson I'm going to teach is on how to keep the snowman from melting (using ice) - so keeping cold and the second will be how to keep the bottle of water warm for my tea (using hot tap water) - so keeping warm.
    I'm worried that I have not fully understood the science behind it and I don't want to explain it incorrectly to the children. I understand that the thermal insulator keeps cold things cold and warm things warm and I understand that this term will need to be used in both lessons. However, what is the difference between the term insulator and thermal insulator and am I right to use thermal insulator with the children?
    I read in a science subject knowledge book (there's not much on this topic in there) that the thermal insulator prevents transfer of heat between objects. Now if i explain this to the children they will probably say that the ice is cold so how can it give out heat. I have no idea how I would respond to this, probably because I don't think I understand this myself! Could anybody please help me understand this?
    Thank you in advance

     
  3. T34

    T34 Established commenter

    You do seem to be trying to introduce two ideas at once.
    The two ideas inherent in your post are
    1) No heat transfer occurs between two substances at the same temperature.
    Your snowman will not lose heat to ice. Your hot bottle will not lose heat to hot water.

    And
    2) An insulating substance (thermal insulator if you want to be precise) decreases passage of heat from a hot area to a colder area.
    My advice would be to get yourself quite clear about these two ideas and deal with only one of these ideas at a time.
     
  4. phlogiston

    phlogiston Star commenter

    Hi,
    Insulator (have to be careful not to type insulter) is a general word for something that stops energy getting through, so I can think of electrical insulators, thermal insulators and sound insulators.
    No doubt some learned people will add to the list.
    Heat transfer always happens from hot to cold.

    If you have an ice cube you are trying to prevent heat from the surroundings warming it up and melting.
    On the other hand a cup of coffee has more heat energy than the surroundings, so is losing the energy to the surroundings. An insulator will slow that process down so the coffee stays warm for longer.
    I currently wear thick socks so that my feet don't lose energy to the surroundings faster than my blood keeps them warm.
    Hope that helps.
    Best wishes for a happy new year,
    P
     
  5. blazer

    blazer Star commenter

    Insulator has two applications as does conductor. The first is in the transmission or blocking of heat and the other regarding electricity. So if you are dealin with heat then Thermal insulator would be the correct term to use. The difficulty where kids are concerened is the idea that cold = the absence of heat. Kids frequently think that 'cold' can travel in the same way heat travels. The ice cube does not melt because heat from the outside cannot get through the insulatuon to make it melt.

    If you want a starter then you could show them a picture of two snowmen, one 'bare' and the other wearig a nice warm coat. Ask them which will melt first and I bet all will say the one wearing the coat because the coat will keep it warm. (And probably half of yr 11 kids will say the same)!
     
  6. Henriettawasp

    Henriettawasp New commenter

    ... and they would be quite correct.
    Answer in simple steps (physicists - lets keep this simple [​IMG] )
    1. Heat energy moves from a warmer object to a cooler one. ( If you understand particle theory you can add that in warmer materials the particles are moving faster).
    2. Your snowman is colder than the surrounding air - so heat energy will move from the air to the snowman - eventually warming and causing it to melt.
    3. Your bottle of warm water on the other hand will be warmer than the surrounding air, so heat energy moves from the bottle to the air, your water thus loses energy as it cools.
    4. By placing a thermal insulator between the snowman/ hot water bottle you are reducing the transfer of heat energy to and from the surroundings. So the cold thing stays cold, the hot thing stays hot (for a while at least).
    Yes. The other type of insulator you encounter at KS2 will be electrical insulator- although you are not wrong if you just refer to an 'insulator'.
     
  7. blazer

    blazer Star commenter

    Another problem that I have encountered with kids understanding is in which direction heat travels, They have a big problem with the idea that heat travels from where it is cooler to where it is warmer (Endo and exothermic reactions need this understanding). Give them and ice cube to hold and they think that the 'cold' flows from the ice cube into your hand.
     
  8. Henriettawasp

    Henriettawasp New commenter

    ... what the...? No answers for over an hour then 4 in as many minutes! We science teachers must hunt in packs...
     
  9. Henriettawasp

    Henriettawasp New commenter

    Good point. How do you deal with this one, blazer?
     

  10. Have you considered using the same insulator to keep a hot thing hot and a cold thing cold?
    If
    you ask the class which snowman melts first, the one with a blanket
    around him or the one without, they will likely say the one with.
    The one without the blanket will melt first, because the blanket stops heat transferring to the snowman from the air around him.
    I realise this is counter-intuitive for many and I know from secondary colleagues that their students struggle with it as well; however I suspect that your idea of using ice to keep ice cold and hot water to keep a hot thing hot wopuld only serve to enforce the misconceptions.
    I've done this with cotton wool as an insulator, two tins/jars whatever, both with hot water. Wrap one in cotton wool and see which cools fastest.
    Then repeat with ice (or icy water) - the non-insulated one warms up more quickly.
     
  11. O.K. bit of basic Physics: Heat is a form of energy and it has difficulty in passing through an insulator. It passes easily through a conductor. Electricity is also a form of energy and it also passes throgh difficuly through an insulator but passes easily through a conductor. Now different materials behave as good conductors or good insulators with regard to these forms of energy, thus we define thermal conductors and thermal insulators with regards to heat, and electrial conductors and insulators with regard to electricity.
    When heat energy is added to a piece of mateial, its temperature rises. When it is removed the temperature of the substance falls. Now the rate at which head enters or leaves a piece of material depends on all sorts of things but as far as we are concerned we will concentrate on two things: the difference in temperature between the object and its surroundings and the insulating properties of any insulator - thermal insulator - with which it is surrounded.
    Having explained this, you can follow that if we pour some hot tea into a cup, it won't be too long before it is too cool to drink. If however we pour the same quantity of hot tea into a thermos flask it will remain hot enough to drink for hours and hours. This is because the thermos flask is an extremely good insulator and reduces the rate at which the heat energy leaves the tea to a very low rate. (It must leave the tea because the tea is at a higher temperature than its surroundings)
    I hope that helps.

    O.C.
    I hope that this helps
     
  12. Hi Taspat

    Good luck with the lessons and thanks for caring enough to sort this out (my daughter is at exactly the same stage as you so I can imagine how you are feeling ... but would like to feel that I'd want to help anyway!)

    A couple of points ... you are quite right about insulators ... and the opposite idea - "conductors". As far as most school science is concerned - and certainly for primary - this comes up in two contexts - thermal insulators and electrical insulator. A thermal insulator prevents (or better - reduces to a tiny amount) heat transfer and an electrical insulator does the same to an electrical current. So, yes, you are technically right to use the term "thermal insulator" - but once the children understand what you are talking about, you could probably drop the "thermal" bit - and not be wrong.

    Now then ... just think why the snowman would melt .... it's the heat coming in from the surroundings, which are warmer, which could melt the snowman ... so if you put clothes on it you will reduce the rate at which heat is transferred in... or in an experiment, you could use different types of insulation, different thicknesses, different intensity of lamp shining on it (of course, changing only one at a time).

    Hope this helps ... post again if not

    Good luck

    *****
     
  13. Henriettawasp

    Henriettawasp New commenter

    .. or do you leave it to the biologists to explain about sensory neurons? [​IMG]
     
  14. T34

    T34 Established commenter

    And they are not wrong, either.
    They are just using a different paradigm.
     
  15. Blimey ... there were no replies when i started typing!
    Apologies for repeating what everyone else has said
     
  16. blazer

    blazer Star commenter

    I give them something warm like a beaker of hot water to hold. They have no problem working out which way the heat flows in that. I get them to work out which object is getting cooler (the beaker) and whuich part is getting warmer (their hand). The apply the same thinking to the ice cube/hand situation.
     
  17. blazer

    blazer Star commenter

    Then I use the joke!


    Posh Spice gives David Beckham a thermos flask for his birthday. David doesn't know what it is so Posh tells him 'it keeps hot things hot and cold things cold'. David takes it with him to training next day and the Coach asks 'What's that David' "It's a thermos flask, it keeps hot things hot and cold things cold" says David. "So what have you got in there then" asks the Coach "A choc ice and a cup of coffee" Says David! (You have to be able to do the Becks accent)!
     
  18. T34

    T34 Established commenter

    Snowman?
     
  19. I don'tthink the school will have equipment like that, I think I will just have to use ice cubes and get them to pretend its a snowman and get the children to measure them every 15 minutes. Thank you for all your help.
     
  20. Hi everyone
    I taught my year 4s the keeping cold lesson and it went quite well and they all seemed to understand it so I would just like to thank everybody for their help.
    I need some further help and hoping somebody could help. In the next science lesson we will be investigating how to keep a bottle of warm water warm. I'm going to use bubble wrap, foil, newspaper, felt and cling film. Which is the material that should be the best thermal insulator, is it the bubble wrap? Should I stick to these materials or should I use some different materials?



     

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