Can someone get bunsen burners

Basic license for laboratory technology

Handling chemicals

There are a few things to keep in mind:

  • The aim is to use as little of the chemicals as possible!
What we want to observe, we can usually see even in small amounts. That's why we always try small amounts first. If there is a suspicion that the amount of chemicals is influencing the experiment, you can try more, but that does not mean that "everything" is used.
The fewer chemicals that are used, the less waste there is.
  • Do not contaminate chemicals!
Use a separate spatula (or spatula side) or pipette for each vessel.
Get the required amount of chemicals out of the jar onto a (once) folded sheet of paper (size as required).
  • Dispose of chemicals correctly!
Asks how to dispose of the chemicals. Usually this is announced in advance.
Contaminated glass vessels that can no longer be cleaned can be disposed of in the residual waste if the chemicals are harmless, e.g. sulfur, carbon, magnesium oxide.

Disposal rules

Some more detailed information and typical errors:

Get to know devices

Memorize device names

In order to be able to use the experiment instructions, you need to know the names of the devices that are mentioned there. You are expected to memorize the names of the devices and also learn how and for what it is used. The most important information is still on this page, but you can also go to the Wikipedia page Laboratory device.
  task

Use the book on page xxx to fill out the following worksheet. As you continue reading this page, take notes on what the devices are used for.

ATTENTION, control !! - Show your knowledge of the device names!

In Moodle you will find a task with a representation of an experiment. Do you recognize all of the devices that are in use? The control is done by the teacher.
 

  

Materials and shape of devices

In most cases, it is specified which device must be used. To make it easier for you to remember why you are using which device, a few general tips.

About the material:

  • Glass is above all heat and chemical resistant. So you can heat it up and add almost all chemicals to it without attacking the glass. However, a hot bunsen burner will soften and melt normal glass over time. But there are special types of glass that can withstand more heat, such as "Durex" or "Fiolax".
  • Wood it is flammable but it conducts heat poorly, so you can use wooden objects if you want to touch something hot (without a flame).
  • metal is above all stable, but conducts heat well. So it is more likely to be used for devices that are used to attach or hold something. But mostly not in direct contact with the flame.

To the form:

  • The Beaker with its vertical walls it is easy to fill because it has a large opening. Here you can easily put something in, or put something in it.
  • The Erlenmeyer flask is especially useful when you want to move the content by hand. Due to the small opening, you can grab the Erlenmeyer flask by the neck and swing it around. Due to the shape, something cannot slosh out that easily.
  • The Round bottom flask cannot stand alone and is therefore always attached to a tripod.
  • For simple heating over the Bunsen burner, vessels with a flat bottom are usually used, which stand on a tripod on which a glass ceramic plate or a wire mesh again lies.

About the size:

  • If you want to heat something, the vessel must not be too full. Liquid chemicals in particular tend to boil over quickly. You can also prevent boiling over with boiling stones.
  • Test tubes are used for very small quantities.
ATTENTION, control !! - Show your knowledge of the devices!

In Moodle you will find a crossword puzzle that not only asks for the device name but also goes into the materials.
 

  

Handling test tubes and accessories

The English name for test tubes shows what they are intended for: "Test Tubes" ... that is, test tubes. Test tubes are usually used primarily for examining small quantities. In school, however, reactions are also carried out in it, as it is a small vessel and therefore only little material is used. You can also observe the material in it.

Important information about handling:

  • If you want to heat a liquid in it, the test tube should be less than half full. Otherwise there is a risk that the liquid will boil over slightly (see boiling delay). You can also use boiling stones.
  • When heating over the Bunsen burner, you always have to move the test tube a little out of your wrist so that it is not permanently in the hot flame. Otherwise the small amount of liquid would boil too quickly.
  • The test tube is handled with a wooden test tube chamber, as wood is a poor conductor of heat. The clamp should be attached to the upper curved edge (beaded edge) so that the test tube cannot slip. Crucible tongs are not suitable for holding, but you can use a tripod with a suitable clamp.
  • When heating, make sure that the opening of the test tube is not pointing at someone else - warn them if they go into the area where the liquid might spill.
  • The opening should also not be held in such a way that you meet yourself or the liquid sloshes onto the Bunsen burner so that the flame can go out.
  • If the contents of a test tube are not overheated, a water bath is used. A beaker is filled with water that is heated (Bunsen burner or stove) and thus a maximum temperature of 100 ° C is obtained.
  • Test tubes are generally not placed on the table as they can roll away. You put it down in a test tube stand and remove the clamp for this purpose. It is annoying because you can easily bump into it and knock everything over. Also, their weight alone could cause a lightweight stand to tip over.
  • If you want to pick up a test tube after heating it, you should carefully feel your way from top to bottom so that you don't accidentally touch the hot glass.
  • If you have something in the test tube that you want to shake, you should not use your thumb or hand to close it. You look for a suitable stopper that you hold on to, no matter how well it fits. It can quickly happen that some pressure is created (when a gas escapes) and the stopper flies out. If you put the test tube with the stopper down, you can possibly release pressure (open briefly and put the stopper on again). If you are a little skilful, you can mix the contents without a stopper by "snapping" the test tube from your wrist.
  • Regardless of whether it is a solid or a liquid: you always have to know how a substance behaves when it is heated. If this is not known, you should go into the fume cupboard to be on the safe side, as toxic or strongly smelling gases could be produced. Alternatively, an absorber with a well-fitting stopper could be used to catch the gases that are generated. Simply put a balloon over the opening.
  • Test tubes are amazingly stable, but if you heat them up and then suddenly cool them down (cold water, cold table top) the material contracts so quickly that it breaks. Therefore, always let a test tube cool down before washing it or cooling it with ice. You can also use lukewarm water to lower the temperature a little.
  • Test tubes must be cleaned with a suitable brush. If there is some dirt or if the glass has been deformed due to excessive heating, cleaning is not worthwhile. Ask the present teacher whether cleaning is possible or makes sense. Finally, they are rinsed with clear water and hung up to dry.

Types of heating

Depending on your needs, there are different ways to heat something.

You heat up quickly with that Bunsen burnerwhose flame can reach temperatures of up to 1300 ° C when the air supply is open.

Test tubes are often held directly in the flame, but all other glass devices, especially for longer heating, are usually only above one Ceramic mesh or one Glass ceramic-Plate (brand name e.g. "Ceran") heated.

Of course you can too Electric heating plates can be used, which can be regulated well, but then the vessel needs a smooth bottom. For round bottom flasks will be Patio heaters which are only suitable for a certain size of round bottom flasks. In this way, the lower part of the vessel is heated evenly. See picture below plus another form of patio heater that can be attached to the tripod.

If temperatures that are too high are not desired or if an upper limit has to be adhered to, the following options are available:

  • In one water bath the vessel is heated indirectly. The surrounding water reaches a maximum temperature of 100 ° C and thus the vessel is not heated any more.
  • Instead of water, you can also use oil, which (depending on the type) boils at around 300 ° C. However, the oil must not evaporate, which is why a thermometer should check the temperature.
  • For higher temperatures, sand or graphite dust can also be used to transfer the heat.
  • Erlenmeyer flask on ceramic wire mesh over Bunsen burner


It should also be noted that when heating flammable liquids no bunsen burner may be used.

Cooling options

The most common coolant used is water. It is mainly used to cool heated and hot objects. ATTENTION: If you cool a hot glass too quickly, it can burst.

If you want to have lower temperatures, use frozen water, i.e. ice. Mixed with certain salts, frozen water can also reach temperatures below 0 ° C. See template: WP cold mix and With cold mix there is also ice in summer

In professional laboratories, frozen carbon dioxide (dry ice) or liquid nitrogen is also used. Since both substances are gaseous at room temperature, they leave no pollution behind when they have evaporated.

Measuring liquids

There are various ways of determining the volume of liquids.

  • With the Measuring cylinder ... it is the most flexible, because it is easy to fill and you can measure different quantities with it.
  • With a volumetric flask ... usually a bottle with a round belly and long neck. It always has only one measuring line and is mostly used to prepare measuring solutions. These are solutions with a certain concentration.
  • With a Graduated pipette ... especially when it comes to small amounts of liquid, pipettes are used. With a so-called Peleus ball you can draw liquids into the pipette and read them on the scale. It is important to keep the reading point at eye level. By the way, pipettes are usually calibrated for the outlet, which means that the scale takes into account that some of the liquid remains in when it runs out. So you shouldn't blow, squeeze out or shake everything.
  • With a Volumetric pipette ... it is intended for a certain amount, because it has only one measuring line.

The images can be clicked to see them larger:

When using it, it is essential to pay attention to two things:

  • You have to bring the vessel to eye level, because if you look at it at an angle or if you hold the vessel at an angle, you will read wrongly.
  • Make sure that you read the lower edge of the "meniscus", at the deepest point. This has to do with the fact that the water wets the surfaces.
  • On some measuring devices, such as the one not mentioned yet burette, there is a strip that runs vertically from top to bottom, making it easier to read. It is called the Schellbach Stripe (see picture).
  • Schellbach stripes make reading easier

To use the Peleus ball:

Reading exercise:

Bunsen burner operation

Applications to the bunsen burner

Weighing with different scales

Electric scales

Pharmacist scales

Use for weighing: Density determination

Since the density is defined as the quotient from Dimensions and volume Now that you know how to weigh and measure volumes, you can perform some tasks on it.

As an introduction to practical density determination, two worksheets:

The little plaster 1x1

As an inexperienced laboratory technician, you should read through my tips on how to get the glassware really clean. Because I'm sure you, too, prefer clean glass appliances to smeared and sticky ones.

  • Mechanical cleaning is usually the most important.
Even water and loads of washing-up liquid won't help if something insoluble sticks to the wall. On the other hand, it is quick and easy if you use brushes (bendable!), Sponges and rags.
  • Always rinse well with clean water
It is easy to "overlook" dissolved salts. Therefore, always fill the container used several times with water and then empty it again. Of course, rinse the outside as well.
  • Place to dry or hang up after cleaning
This allows the water to run off and does not leave any water stains. Since it takes time for the vessels you have cleaned to dry out, you don't have to wait; you can then clear away any dried devices that have come from other people. Glass utensils are never actually dried off because it takes too long and is unnecessary.
  • Detergents are not always necessary!
Dish soap is especially helpful when you have a greasy soiling. But it can also help a little with other types of dirt by reducing the so-called surface tension. But mechanical processing is still more important than washing-up liquid - it is enough smaller Drops, otherwise the detergent may be left behind as an impurity.
  • Clean tables from dirt!
Remember, the next person to use the table will not know what chemicals you used. So clean the table carefully, first with a wet cloth and finally with a rinsed and well-squeezed cloth to get the table reasonably dry. Subsequent drying with paper towels is then not necessary.
  • Paper towels are only there to dry your hands!
These paper towels are not intended for cleaning tables and equipment, there are cleaning cloths and rags. Used paper towels belong in the Residual waste bin!!