Is it correct that the mouth of the test tube should be slightly inclined upwards when heating the s

It depends. 1. When heating the solid, the mouth of the test tube is downward.

When heated, the temperature of the air in the test tube will rise, and the temperature of the water vapor in the air will also rise, and when it hits the wall of the test tube with a lower temperature, it will liquefy into water droplets and attach to the wall when it is cold.

This water is formed by the exothermic liquefaction of water vapor at high temperature hitting the low temperature pipe wall, which becomes condensate.

If the nozzle is upward, the condensate will flow back to the bottom of the tube, and since the bottom of the tube is the hottest (closest to the flame), the condensate will burst when it hits the cooler condensate.

In summary, the mouth of the heated solid test tube should be downward.

2. When heating the liquid, the mouth of the test tube is upward.

There's nothing to say about this, if you go down, the liquid will all be poured out.

If a liquid substance is being heated, the mouth of the test tube must be upwards or the liquid will flow out, and if a solid substance is heated, it must be slightly inclined downwards.

It should be said that when heating a solid substance, the mouth of the test tube should be slightly inclined downward; [Prevent condensate from flowing backwards to the bottom of the test tube when heating the solid matter, causing the test tube to burst.] 】

When heating a liquid substance, the mouth of the test tube must be tilted upwards and at an angle of 45° to the tabletop.

Not necessarily, depending on the state of reactants and products, it is necessary to slope downwards to form liquid water.

Yes, that's generally the case.

To heat a liquid substance, the mouth of the test tube should be tilted upwards - the purpose is twofold, one is to make the liquid in the test tube more heated. Second, it can prevent the liquid coming out of the nozzle from flowing to the alcohol lamp during boiling.

The heating area is increased, and the test tube is evenly heated.

1. When heating the test tube, the test tube touchesAlcohol lampsWick: (tube rupture).

2. When heating solid drugs, the test tube mouth is tilted upward: ( Condensate at the test tube mouth.

Reflux vessel tube rupture).

3. Immediately rinse the heated test tube with cold water: (the test tube is broken).

There will be no exaggeration as bursting the test tube, the heating solid is volcanic and bent to prevent the condensate from flowing backwards, the general test tube mouth is slightly downward, if it is up, the water is not much due to the natural evaporation of the test tube due to high temperature, if the water flows more to the bottom of the test tube, the bottom may be broken due to instantaneous cooling. Cracking and bursting are not the same thing, be careful with the proper wording.

Direct heating. It is suitable for experiments where there is no precise requirement for temperature and rapid temperature ramp-up, including asbestos netting.

Heating and heating without asbestos netting.

It is suitable for those who can not use open flame heating to have higher environmental requirements and can not have impurities involved, high-quality heating, vacuum induction heating is a case, usually indirect heating methods are, lack of electromagnetic induction heating, thermal radiation heating, these backheating methods do not need to contact with objects, also known as indirect heating.

Prevents the generated condensate from backflowing. Analysis: Analysis based on the formation of water during the heating process of the solid in the test tube, and the backflow caused the test tube to burst.

Answer: When heating the solids, if the mouth of the test tube is not slightly inclined downward, the condensate will flow backwards to the bottom of the test tube, causing the bottom of the test tube to rupture. Therefore, when heating the solids in the test tube, the nozzle should be tilted downward.

Precautions for heating solids in test tubes.

1. Before heating, the outer wall of the test tube needs to be wiped dry to prevent the test tube from bursting during heating.

2. The method of preheating is to move the test tube back and forth on the flame; For the tube that has been immobilized, the alcohol lamp can be moved.

3. Whether it is heating or preheating, the external flame of the alcohol lamp should be used; Do not allow the tube to come into contact with the wick during the entire heating process to avoid the tube bursting.

Prevents the tube from bursting due to the backflow of liquid.

Test tubes, commonly used instruments in chemical laboratories, are used as reaction vessels for a small number of reagents, and are used at room temperature or when heated (they should be preheated before heating, otherwise the test tubes are easy to burst). There are many types of test tubes, such as ordinary test tubes, supported test tubes, and centrifugal test tubes. The specifications of ordinary test tubes are expressed in outer diameter (mm) and length (mm), such as 200, etc.

A flat-mouth test tube is a flat-mouth glass tube with a round bottom and a melted nozzle. Flat mouth, easy to disinfect and kill bacteria at the nozzle.

A roll-top test tube is a round-bottomed glass tube with a crimped (or round) mouth. The roll (or round mouth) is used to increase the mechanical strength, and at the same time to facilitate the clamping and not easy to fall off.

It is a flat-mouthed, round-bottomed test tube with a thin and short diameter (diameter 6mm, length 30mm).

The tube is a flat-mouth test tube with a side branch tube, and its side branch tube is mainly used to connect with the suction pipe, and the nozzle is inserted into the filter funnel with a rubber plug with a hole to replace the micro-filter bottle and serve as the receiving bottle for micro-filtration. Graduated test tube: It is a round-mouthed test tube.

The capacity scale marking is engraved on the tube body, and the measurement number can be read directly, which is easy to use.

When filling the solution, it should not exceed 1 2 of the volume of the test tube, and when heating, it should not exceed 1 3 of the volume of the test tube.

When using a dropper to add liquid to the test tube, it should be suspended and not extended into the mouth of the test tube.

When heating the solid drug in the test tube, the mouth of the test tube should be slightly inclined downward, in order to prevent the condensate from flowing back to the bottom of the hot test tube and bursting the test tube a. When heating the solid, the mouth of the test tube is slightly inclined downward, in order to prevent the condensate from flowing back to the bottom of the hot test tube and bursting the test tube, so the option is correct b. When heating the solid, the mouth of the test tube is slightly inclined downward, in order to prevent the condensate from flowing back to the bottom of the hot test tube and bursting the test tube, rather than convenient for heating, so the option is wrong c. When heating the solid, the mouth of the test tube is slightly inclined downward, It is to prevent the condensate from flowing back to the bottom of the hot test tube and bursting the test tube, rather than conducive to gas discharge, so the option is wrong D. When heating the solid, the mouth of the test tube is slightly inclined downward, which is to prevent the condensate from flowing back to the bottom of the hot test tube and bursting the test tube, rather than preventing the air from flowing backwards, so the option is wrong So choose: a

Prevent condensate from backing up into the hot tube and bursting the tube.

Because there may be water generation or solid drug moisture when the solid is heated, the water vapor condenses into a liquid state at the mouth of the test tube, if it is facing up, the liquid water will flow into the bottom of the test tube, so that the test tube is heated unevenly and bursts, so the mouth of the test tube should be downwards to prevent the water from backflowing and bursting the test tube

Prevents liquid water from backing up to the bottom of the tube and causing tube rupture.

Yes, when heating solid substances, the mouth of the test tube should be downward, in order to protect the safety of the test tube and you, because if you are diagonally upward, the heated substance will be generated by water, or evaporate to the mouth of the test tube and condense into droplets, which will flow back to the bottom of the test tube and cause uneven heating, and the test tube will burst and hurt people, so the correct operation is to obliquely downward! Hope to adopt!