If there is water on the outer wall of the test tube during heating, can it be heated without wiping

No! Our teacher emphasized many times that heating directly without wiping dry will cause the test tube to burst! To wipe dry, preheat.

What are the wrong things that can cause a test tube to burst?

There are nine types of errors.

1) The iron clamp holding the test tube is too tight, leaving no room for the test tube to be heated and expanded, so that the test tube will explode due to heated expansion.

2) There is water on the outer wall of the test tube that has not been wiped dry. When heated, the outer wall of the test tube is dried in some places first, and some places are dried later, which causes the test tube to burst due to uneven heating.

3) When heating the solid drug in the test tube, the mouth of the test tube is not slightly inclined downward, because there is water generation in the reaction process or the original solid drug contains wet water, the water flows from the mouth of the test tube to the bottom of the test tube and causes the test tube to burst.

4) When heating the liquid in the test tube, the liquid in the test tube exceeds one-third of the volume of the test tube, and the liquid escapes from the test tube and spills on the outer wall of the test tube during the heating process, causing the test tube to burst.

5) When heating the test tube, the whole test tube is not evenly heated first, but directly heats the test tube where the drug is placed in the test tube, which causes the test tube to burst.

6) When heating the test tube, the flame core of the alcohol lamp comes into contact with the test tube, causing the test tube to burst.

7) Placing a hot test tube on a table or test tube rack causes the test tube to burst.

8) During the experiment, there is a cold liquid splashed on the heated test tube or the hot test tube has not cooled, if it is washed with cold water, it is likely to burst.

9) When the gas is collected, the gas is collected by the drainage method, and when the gas is collected, the air duct is not taken out of the water tank, so that the alcohol lamp is removed first, so that the cold water enters the test tube along the air duct, which will cause the test tube to burst.

No, just heat it directly.

The test tube is to be preheated anyway, so let's bake it dry, but what's so hard about wiping it.

If there is water on the outer wall of the test tube, the test tube is prone to bursting when heated.

When heating the liquid in the test tube, do not put the mouth of the test tube at the person, because the liquid in the test tube may be sprayed out during the heating process and burn the person.

After taking off the alcohol lamp cap for a period of time, I went to light the fire again, and found that the alcohol lamp was not ignited because the alcohol on the wick had already volatilized, and only water remained. After the experiment, the instrument after the experiment is stained with drugs, which may affect the results of other experiments; The instrument must be cleaned because it is not clean, which will affect the results of the experiment.

Precautions for using test tubes.

1.The outer wall of the test tube should be wiped dry before heating, preheated first and then heated, and should not be quenched after heating. Instruments that can be heated directly in the laboratory are:

test tubes, incendiary spoons, evaporation dishes and crucibles, etc.; The asbestos nets that need to be padded are: beakers, flasks, Erlenmeyer flasks, etc.; Instruments that cannot be heated are: funnels, measuring cylinders, gas collection cylinders, etc.

2.When heating, the tube clamp or iron clamp should be clamped in the middle and upper part of the tube.

3.When heating solids, the mouth of the test tube should be slightly tilted downward.

4.When heating the liquid, the liquid should not exceed 1 3 of the volume of the test tube, and the nozzle should be at an angle of 45 degrees to the tabletop, and the nozzle of the test tube should not be facing yourself or others.

Because if the liquid in the test tube boils and splashes outside, it may get to people, and some liquids are harmful to the human body, so it should not be directed at people.

For safety reasons, no matter what the heated liquid of the test tube is, the boiling liquid and hot gas after reaching the boiling point are very likely to rush out of the test tube, and if it is directed at a person, the boiling liquid or hot gas will burn people.

When heated, the liquid may evaporate and the front side is likely to be inhaled. There are some chemical reagents that can cause violent reactions when heated, either positively or to people**.

Thermal expansion and contraction, cold water washing, local cold fast, temperature difference is too large, resulting in the deformation of the test tube, and the test tube will burst in an instant.

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.

Precautions: Keep the outer wall of the test tube free of water droplets when heating to prevent bursting due to uneven heating. After heating, the tube cannot be washed before it has cooled to room temperature.

When using a test tube clamp to clamp the test tube, the test tube clamp is sleeved from the bottom of the test tube to the top and clamped in the middle and upper part of the test tube.

Answer: When the test tube is heated, the outer wall must be dry and waterless

Because: when there are water droplets on the outer wall of the test tube, if it is heated, the result will be that the test tube will burst. The reason is that the test tube is heated unevenly.

There is water on the outside of the test tube, which can easily cause the test tube to be heated unevenly and cause the test tube to burst

So the answer is: no; Prevents the tube from bursting when heated

Notes:

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

2. Use a test tube clamp for heating, and the mouth of the test tube should not be facing people. Tilt about 45° when heating the liquid.

3. The heating should be even, so as not to boil or the test tube burst.

4. It cannot be quenched after heating to prevent rupture.

5. Preheat when heating to prevent the test tube from bursting due to sudden heating.

6. Keep the outer wall of the test tube free of water droplets when heating to prevent uneven heating and bursting.

7. After heating, the test tube cannot be washed before it has cooled to room temperature.

8. External flame is applied for heating.

The main purpose of the test tube.

1) Hold liquid or solid reagents.

2) Heat a small amount of solid or liquid.

3) Prepare a small amount of gas reactor.

4) Collect a small amount of gas.

5) Dissolve a small amount of gas, liquid or solid solute.

6) Centrifugation is used as a container.

7) Used as a reaction vessel for a small amount of reagent, at room temperature or when heated.

1. The capacity cannot exceed 1 3 of the test tube;

2. It should be fixed with a firm bracket to prevent dumping;

3. Heat slowly to make the test tube evenly heated;

4. When using the test tube clamp for heating, the mouth of the test tube should not be facing the person to prevent the liquid from splashing and hurting the person;

5. The heated test tube should not be cooled down suddenly to prevent the test tube from rupturing;

6. Wipe the pipe wall clean before heating, and it is strictly forbidden to have water;

7. The outer flame of the alcohol lamp should be used when heating.

Here are a few things to keep in mind:

1. The mouth of the test tube should not be tilted towards people.

2. The heating should be uniform.

3. The liquid or solid in the test tube should be less, and the solid should be flattened evenly.

4. Do not let the liquid burst to splash out, and take the test tube away in an emergency.

When heating the liquid in a test tube, pay attention to the following points:

When heating the liquid medicine in the test tube, the test tube should be clamped with a test tube clamp, or the test tube should be fixed on the iron frame with an iron clamp.

Do not exceed one-third of the volume of the liquid drug in the test tube to prevent the liquid drug from escaping from the test tube during the heating process or when the liquid is boiling.

Before heating, wipe the water on the outer wall of the test tube to avoid the test tube being heated unevenly and bursting during heating. Put the test tube clamp from the bottom of the test tube, and clamp it about 1 3 places (or middle and upper part) from the test tube mouth, preferably 2 cm away from the test tube mouth. When heating, pinch the long handle by hand, and your fingers cannot touch the short handle.

When heating, the test tube should be tilted, and the tilt angle should be 45° angle to the tabletop.

When heating, the test tube should be heated evenly, and then the middle and lower parts of the liquid in the test tube should be carefully heated, and the test tube should be moved up and down from time to time. When the test tube is fixed on the iron frame, the alcohol lamp is held in hand and the alcohol lamp is moved up and down from time to time in the middle and lower parts of the test tube containing the liquid.

The heating part of the test tube should be placed on the outer flame part of the lamp flame, and the bottom of the test tube should not be in contact with the wick, otherwise the test tube may break.

In order to avoid the liquid in the test tube from boiling and spraying out and hurting others, do not make the mouth of the test tube face yourself or others when heating.

After the test tube is heated, the test tube should be placed in the hole of the test tube rack. Do not place a very hot tube on the tabletop, and do not rinse immediately with cold water to avoid the tube breaking.

1. The liquid in the test tube does not exceed one-third of the volume of the test tube.

2. The test tube is clamped at one-third of the distance from the test tube mouth.

3. When heating, the test tube should be tilted at an angle of 45 degrees!

Fourth, the bottom of the test tube is located at the outer flame of the alcohol lamp and preheated.

5. The mouth of the test tube shall not be aimed at oneself or others.

What are the precautions for heating the liquid in the test tube?

The most important thing is to heat evenly.

Here are a few things to keep in mind:

1. The test tube mouth is inclined and missing, and do not face people.

2. The heating should be uniform.

3. The liquid or solid in the test tube should be less, and the solid should be flattened evenly.

4. Do not let the liquid burst and cause splashing, and take the test tube when it is urgent.

The precautions for heating the inner liquid of the test tube are: the amount of liquid in the test tube should not exceed one-third of the volume of the test tube, the mouth of the test tube should not be towards a place where there are people, and the test tube should be sleeved from the bottom to the top when clamping, and the sleeve should be set at a third of the distance from the mouth of the test tube The test tube is at an angle of 45 degrees to the table top When it starts to heat, it should be preheated, and then the middle and lower parts of the liquid should be heated evenly by moving the test tube without moving the test tube to heat the outer flame of an alcohol lamp If the mouth of the test tube is facing a place where there are people, the liquid will hurt people due to splashing outward

So the answer is: where there are people