This is to ensure even and controlled heating of the reactants. Things that can go wrong include bumping, where one area becomes hotter than the others, and boil over, when the reactants are heated evenly but too strongly.
Consider that the liquid may suddenly boil at the point of contact with the area that the flame is heating, the boiling (massive change in volume of the liquid concerned to become a gas) will eject the liquid/gas at a high temperature in a dangerous manner. The movement of the test tube therefore can keep the liquid mobile (assist convection) and ensure that a larger surface area is being heated to reduce the Watts/sq cm heat transfer to the liquid.
Also consider that test tubes are made of glass (normally similar to Pyrex {trade-name}which is much superior to normal glass). Glass is a poor conductor of heat, as opposed to metals such as copper which are good conductors of heat. All materials will expand/contract to some degree with the application/removal of heat. So heating a poor conductor will in the case of a glass test tube tend to expand the surface where the flame impinges. Glass being a poor conductor means that heat in glass travels slowly and the temperature of the glass may be much cooler where the flame does not reach. The differential expansion of glass (glass being also a very brittle material) will or rather can cause cracking/ destruction of the test tube. Moving the test tube in the flame tends to heat more area of the glass and more uniformly. Test tubes normally have very thin walls. It is always better to apply heat with a small flame just to be sure. Consider a bi-metal strip of which one side expands greater than the other although it is being heated at the same rate and is actually the same temperature, these types of metals are not brittle, so the bi-metal strip just bends. If however you tried to make a bi-metal strip with cast iron and copper, it would fail because of the differential expansion of the different metals and the overriding fact that the cast iron side is very brittle and will break (fail) as the copper will force the cast iron to one side (bend) and the brittleness of the cast iron cannot take such distress.
To heat all parts of the test tube evenly.
See the Related Questions to the left for more information about test tubes.
Scientists use test tubes in order to test a larger sample. This allows them to try new things and new chemicals against the sample.
When heating a testube in a Bunsen flame the testtube should be gently moved to avoid any part of the liquid becoming gas and exploding the rest of the liquid on to you neighbour.
Because it is too hot to handle with your fingers if it has been in a hot or boiling water bath.
Wear goggles and a laboratory apron Hold the test tube with a test tube clamp not in your bare hand. If the liquid is nonflammable it may be heated in the flame of a Bunsen burner, otherwise a hot water bath over a hot plate may be more advisable. If heating in the flame of a Bunsen burner hold the test tube at an angle and move the tube in and out of the cool area of the flame. Alway point the opening of the test tube AWAY from yourself and others.
Let's say that there is a substance in the test tube that absorbs carbon dioxide okay? So when we respire, we give out carbon dioxide, which is considered quite warm in temperature. The carbon dioxide will be absorbed by the substance so only oxygen will remain inside the test tube. Since oxygen is produced by plants and is from our suroundings, you could say that oxygen is quite cool in temperature. So, the drop of ink will move towards the test tube because the drop of red ink is a type of metal and it will contract when it is cool or cold. So that is why respiration causes a drop of red ink to move towards the test tube. I hope that answers your question guys!
Test tube brush=use for cleaning test tubes
no.
it vapourise from the test tube
Combustion
This would happen because of the process of diffusion. Hydrogen molecules would move from the hydrogen test tube where they are highly concentrated to the air test tube where their concentration is low.
when was test tube first made,when and who?
test tube is classified in to various types namely hard test tube ,boiler test tube,20 ml test tube
perform a tube leak test perform a tube leak test perform a tube leak test perform a tube leak test perform a tube leak test perform a tube leak test perform a tube leak test
You should only heat liquids in the wider kind of test tube known as a boiling tube. Using an ordinary test tube often results in rapid local boiling and consequent shooting out of the liquid, which is known as 'bumping'. That said, many people prefer to move the tube around in the flame at first to prevent uneven heating of the contents, and to produce smoother boiling. There is a very small chance that concentrated heating may put stress on a weak spot in the glass and cause it to break.
Wear goggles and a laboratory apron Hold the test tube with a test tube clamp not in your bare hand. If the liquid is nonflammable it may be heated in the flame of a Bunsen burner, otherwise a hot water bath over a hot plate may be more advisable. If heating in the flame of a Bunsen burner hold the test tube at an angle and move the tube in and out of the cool area of the flame. Alway point the opening of the test tube AWAY from yourself and others.
A test tube (or sample tube) has no errors.
Let's say that there is a substance in the test tube that absorbs carbon dioxide okay? So when we respire, we give out carbon dioxide, which is considered quite warm in temperature. The carbon dioxide will be absorbed by the substance so only oxygen will remain inside the test tube. Since oxygen is produced by plants and is from our suroundings, you could say that oxygen is quite cool in temperature. So, the drop of ink will move towards the test tube because the drop of red ink is a type of metal and it will contract when it is cool or cold. So that is why respiration causes a drop of red ink to move towards the test tube. I hope that answers your question guys!
Test tube brush=use for cleaning test tubes
Test tube holder
Clamping a test tube