Explain why a gas jar can be opened more easily if the metal lid is heated gently first?
152571
By heating the lid is bigger than it was, and bigger than the jar. So the lid is just seems like other bigger jar's.\nEven if you heated the metal lid and the gas together, you will get the same result, as jar's expansion is less than the lid's expansion.
1030054
You would find, if you had a sensitive enough measuring system, that the energy is dispersed through the acid as heat. \n\nWhen acid oxidises metal there is an initial activation energy required to break the metal lattice and that energy nromally comes from the heat already in the system. When the lattice is under stress sit requires far less energy to break down and the activation energy is lower. That means that more heat is retained by the system as heat.\n\nYou can see for yourself that a metal lattice under stress breaks down and oxidises more readily by simply bending an iron nail and dropping it in a few mm of salt water for a few days. The iron will rust almost exclusively where it was bent. That is because the  bend represents a point of stress in the lattice.\n\nWith less energy required to break down the metal alttice the overall reaction becomes more energetically positive and the amount of heat in the system increases.\n\nThe amount of additional heat this represents is tiny, but with an incredibly stable atmosphere and a very sensitive thermometer you would regeister the lost energy as a higher temperature than an identical beaker of acid with an uncompressed spring.
476322
==========\n\nClose a glass bottle with a Cork at normal temperature and than put it in a freezer for one hour.\n\nThe low temperature will cause the gas to contract.\n\nNow try to open it. You will find it very difficult to open it, why?\n\nBecause of reduced temperature air inside the bottle will be contracted and thus the air pressure inside the bottle will decrease. The higher atmospheric pressure will try to push the Cork inside the bottle which will make it difficult to open the bottle.
340829
Food is not properly fried with a cover.  Doing so prevents moisture from escaping, thus making it simmered or boiled rather than fried.  I do prefer to have a lid with my fry-pans because sometimes I like to brown, then reduce the heat for simmering.  Lids can be purchased separately,  although they do not always properly fit the pan.
330815
"Each hob contains one or more coils made of ferromagnetic material. When an alternating current is passed through these coils, a magnetic field of the same frequency is produced. If a magnetic-based pan is placed on the hob, the magnetic field induces a current in the pan. The internal resistance of the pan causes heat to be dissipated, following the Joule effect. Thus it is the pan itself, and not the cooktop, that heats up and cooks the food. Once the pan is removed from the cooktop, the energy transfer stops. The result is a flame-less method of cooking in which it is nearly impossible to start a fire by forgetting to turn off the stove. Parents won't have to worry about their child touching a hot burner because the cooktop surface remains cool. Changing cooking temperatures is achieved quickly because there is no wait for the hob to heat up, only the pan. Since there is no transfer of heat energy between the hob and the pan, less heat is lost into the air, resulting in a more efficient means of cooking, not to mention a more agreeable cooking environment."\n\n\nhope that help?  we just renovated our kitchen and have installed a Miele induction cooktop and it works wonderfully.  It provides much greater control over temperature...and I am still shocked at how quickly water comes to a boil.  Who knew a stove would be so exciting? haha.
544916
Heat the solvent, then it can take more solute into solution than when it's cool.  Then when you cool it, it is supersaturated.
283659
Because the bottle is not really empty, it is filled with air.  The air expands when it is heated because the molecules move faster, bump against each other, and require more space.
43501
Its a Metal, hence responds to / is a conductor of heat.\n\nIts fluid so the expansion per gradient of heat would be highest.\n\n\nAll other liquids are not a conductor of heat ( or as good as mercury)
60139
The colored piece of glass will absorb more light which will heat it up quicker.\n\nLight goes right through clear glass. Very little light/energy is absorbed.
731331
I've heard that its the boiling water that freezes first. \n\nI think because the water molecules are hot (i.e. they are moving fast) the energy (or heat) will escape (move to equilibrium with other items in the freezer) at a faster rate than the water molecules in colder cup of water. \n\nBut really I'm mostly guessing with my explanation.
1161774
because it stops corrosion to the steel which would rust and therefore increases the shelf life of the wire the same as it would mig or gas welding filler\n\ngaz
812891
An open lid will allow more sound to escape and reverberate, and is therefore usually louder.\n\nIt all depends on what you are accompanying.  You will probably notice that solo grand pianists almost always have the lid open.
787545
If the plates were right side up, then the condensation would collect on top of the agar.  \n\nThis might allow for the colonies to merge together, and then you might not end up with well formed colonies that are isolated enough from each other for picking.\n\nI made this mistake in the past.\n\nKeeping the lid ajar is probably not so critical, as the agar tops allow for gas exchanges, as they are not so tight fitting.\n\nIt was fun thinking about your question.  Pass on the good Karma!
473094
Glass is more dimensionally stable - it doesn't expand or contract when the temperature changes - and it can be polished to a very smooth surface.   The finish is a very very thin layer of metal.\n\nRead "The Perfect Machine" by Ronald Florence if you want to learn more.
30165
This really depends on what liquid versus what solid you are heating.  Some liquids are actually less heat conductive that solids.\n\nFor example,  if you have some oil and some aluminum then the aluminum is going to heat up faster than the oil would.
280487
The idea behind fractional sterilization --- in which you heat, cool, then heat again to sterilize a container --- is to catch resistant microorgranisms and spores that survive the first heating.\n\nCertain microorganisms and spores are actually activated by the first round of heating, so if you serially heat, and then cool, it gives the resistant "bugs" a chance to germinate. Once they're "out in the open," you can kill 'em off with a second or third round of heating.\n\nThis site below doesn't completely explain the difference, but it does go through a lot of the general ideas behind sterilizing instruments and other things in a hospital setting.\n\nTake a look...
922727
The reason is that heat causes molecules to move faster - the cold slows them down. Think of it like molasses when it is cold it is really thick and flows slowly - but if you heat it up it thins out and would flow more easily. When molecules are heated they are easier to manipulate. I hope this helped.