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Laboratory Safety and Apparatus
You probably have heard of the word laboratory. Can you tell your friend what goes on in the laboratory? Look at figure below. It shows Marie Curie in her laboratory. Marie Curie discovered the process of radioactivity. Because of this, she won the Nobel Prize for Chemistry in the year 1911. This was the first time a woman won the Nobel Prize. She actually proved that Chemistry is not a preserve of men; that women can also excel in Science subjects!
key competency: The learner is be able to use effectively laboratory equipment and materials to carry out experiments.
The topic Outline
2.1 Definition of laboratory
2.2chemical
2.3 Laboratory safety
2.4 Laboratory apparatus (names, diagrams and uses)
Introduction
Most of the chemicals used in the laboratory are poisonous. Some are highly flammable while others can burn the skin. Also, some of the apparatus and equipment used in the laboratory are highly dangerous and delicate. Below are categories of hazards that may occur in a laboratory:
• Physical hazards
• Chemical hazards
• Biological hazards
1. Physical hazards are dangers caused by equipment such as tables that may cause a person to trip and fall or glassware that can break and cause cuts.
2. Chemical hazards are dangers posed by poisonous chemicals such as some acids and bases and flammable liquids.
3. Biological hazards are dangers posed by exposure to culture, animal and plant tissues and disease-causing microorganisms. We should always strive to avoid these dangers while working in the laboratory
2.1 Definition of a laboratory
Many houses are always built with a number of rooms. Every room is usually reserved for a particular purpose. Some items are kept in certain rooms due to certain reasons i.e. they could be delicate and expensive and can easily be damaged. Similarly, Chemistry is studied in a place known as a laboratory.
A laboratory is therefore a room, building or institution equipped for scientific research or experimentation.
Chemistry as a subject is sometimes learnt through practical activities known as experiments done in the laboratory. In the laboratory, you will find equipment, materials and chemicals which are used when performing these experiments. Chemical substances used in an experiment are known as reactant substances. Students need to conduct themselves with care and in an orderly manner while in the laboratory so as to avoid injuries and accidents that could occur. Safety rules and regulations have been put in place to guide you as a student when using the laboratory.
A Chemistry laboratory is made up of:
1. Preparation room- This is where the teacher usually prepares for the experiment.
2. Storage room - this is where laboratory chemicals are kept. It has a lockable cabinet for safe storage of flammable and volatile materials.
3. Student working area-this area has sinks, gas taps and storage cabinets.
4. Fume chamber or fume cardboard - it is used to carry out experiments involving production of poisonous gases.
5. Teacher’s working counter-this is usually located at the front centre of the laboratory. It is where the teacher carries out demonstrations on experiments.
6. Safety exit - is a passage used in case of a fire outbreak.
7. Shower room- is used for bathing in case chemicals spill on one’s body.
2.2 chemicals
Chemicals are substances usually in solid or liquid forms that are consumed during reactions. They get usedup in reactions during the course of an experiment. E.g. Sodium hydroxide and Hydrochloric acid.
2.3: Laboratory safety
Many laboratory chemicals are poisonous while some easily catch fire. Some of the chemicals are also corrosive when they come in contact with the skin. It is therefore necessary that rules and regulations are followed to ensure your safety and that of the others while in the laboratory. The two common causes of accidents in the Chemistry laboratory are carelessness and ignorance. Accidents can be minimised when safety rules are strictly observed.
Laboratory safety rules and regulations
The following are some of the laboratory rules that need to be respected while in the laboratory:
1. Do not enter the laboratory without the teacher’s permission.
2. Do not run while in the laboratory because you may trip, fall and injure yourself or others in the laboratory.
3. Be polite while in the laboratory; do not push, scramble or fight.
4. Never taste or eat anything in the laboratory as these may cause poisoning or infection. Health check! Always avoid situations that can put your health at risk. Our health must always be given first priority.
5. Always consult your teacher before trying out any experiment, handling apparatus or chemicals to avoid accidents. Do not interfere with other students’ experiments in progress.
6. Do not tamper with electrical, gas or water fittings. Always turn off water taps and gas taps when they are not in use to minimise wastage. Money matters! Help cut costs on electricity, gas and water!
7. Do not smell gases directly. Hold the gas source 15-20 cm away from the nose and waft the gas towards the nose using your palm, then smell carefully.
8. Always hold test tubes or boiling tubes using a test tube holder when heating to avoid being burnt.
9. Never look directly into flasks and test tubes where reactions are taking place because the chemicals might spurt into your eyes and cause injury.
10. Experiments in which poisonous gases are produced must be carried out either in the fume cupboard or outdoor.
11. Label all reagents you are using to avoid confusion. Always read the label on all reagents before you use them.
12. Always use a new spatula each time you are scooping reagents from a different container to prevent contamination.
13. Always keep flammable substances away from flames because they can easily catch fire. 14. Do not put hot materials into waste containers.
15. All solid waste should be properly disposed of. Do not put insoluble materials into the sinks. My environment my life! Proper disposal of wastes ensures an effective working environment.
16. After finishing with a reagent bottle, replace the stopper and return it in the right place.
17. Always clean all the apparatus and bench tops after use and wash your hands thoroughly before leaving the laboratory.
18. Always know the locations and operations of all safety equipment.
19. Report any accidents to the teacher or the laboratory technician immediately they occur for necessary action to be taken.
20. If a chemical gets on your skin or in your mouth rinse it immediately with plenty of clean water.
21. Always extinguish flames that are not in use to avoid accidents and minimise fuel wastage.
22. In case of a serious accident such as a fire or an explosion, walk out calmly and do not congest at the exit.
23. Always wear laboratory coats, closed shoes, goggles, gas masks and gloves when you are working with chemicals, hot liquids or other materials that could harm you
Laboratory safety precautions and warning labels
In the laboratory, there are symbols and labels majorly to warn the users of the potential dangers. Such dangers usually arise due to ignorance of the laboratory rules or careless handling of reagents and apparatus. Many of the reagent containers have warning labels on them. Warning labels are small pieces of instructions of care. It is therefore important to read and interpret the various warning labels and symbols. Some symbols are placed at strategic points in the laboratory.
Figure below shows Laboratory safety symbols and their meanings
2.4 Laboratory apparatus
We use laboratory apparatus for various functions. The word apparatus refers to the set of equipment used by chemists or other scientists to perform experiments. They may be made of metal, wood, plastic or glass. It is important to use the right apparatus when performing a given experiment. One should also be aware of the accuracy of apparatus before using them.
(a) Apparatus for measuring volume
Some apparatus used for measuring volume include measuring cylinder, burette, pipette and the volumetric flask.
(i) Measuring cylinders .
Measuring cylinders are made of transparent glass or plastics. Measuring cylinders have different capacities.They are used for measuring approximate volumes of liquids or solutions
ii) Burette.
A burette is used for measuring accurate volumes of liquids or solutions during chemical analysis. A burette has many calibrations and a tap at one end. The tap enables the user to release liquid drop by drop. The zero mark is at the top of the scale. This is because the burette measures how much liquid flows out
(iii)Pipette
It is used for transferring exact quantities of liquids or solutions during chemical analysis. Different pipettes measure different volumes of liquid. A pipette filler is made of rubber and is used to fill up pipettes to the volume mark and to also empty their content.
(b) Apparatus for measuring temperature - Thermometer
Temperature is measured using a thermometer. There are different types of thermometers, for example:
(i) Clinical thermometer (ii) General-purpose thermometer
In Chemistry, we use general purpose thermometers. Clinical thermometers are used to measure body temperature in hospitals. They have a bend or a constriction to prevent backflow of mercury after use.
A German scientist, Robert Wilhelm Bunsen invented the Bunsen burner in 1854. A Bunsen burner is the most preferred source of heat in the laboratory. It ensures expected observations are made and that the apparatus holding the reagents are neither damaged nor tarnished. A Bunsen burner consists of the following parts: the chimney, collar, air hole, jet,rubber tubing and the base.
Functions of the different parts of the Bunsen burner
1. Chimney - is a hollow metallic cylinder with an air hole near its lower end. It is designed to raise flame to a suitable height for heating.
2. Collar - is a metal ring at the base of the chimney. The diameter of the collar is slightly bigger than that of the chimney so that the chimney can just fit into it. It regulates the amount of air entering the burner by opening and closing the air hole.
3. Base - is made of thick metallic material into which a small hollow metal with a jet is fitted. It supports the burner so that it does not topple. The Bunsen burner is usually connected to an external source of laboratory gas by the rubber tubing. The gas is supplied consistently and the size of the flame is controlled by the size of the air hole. Air mixes with gas if the air hole is open. The size of the air hole is adjusted by the collar. This way, the temperature of the flame can be altered
How to light a Bunsen burner
A Bunsen burner is lit following certain steps so as to ensure no fire accidents occur. Caution! The process of lighting the Bunsen burner should be carried out with extreme caution to avoid unnecessary accidents
Activity
Flames of the Bunsen burner
A flame is the visible, part of a fire. The flame produced when the air hole is closed gives much more light than the one produced when the air hole is open. Soot is observed under the test tube held on the flame produced when the air hole is closed. The other test tube remains clean.
With the air hole closed, no air enters the chimney. The flame produced is bright yellow, large and unsteady. This flame gives out light and is described as luminous flame. This flame gives out light because of the unburnt carbon particles in the flame. The particles are due to incomplete combustion resulting from insufficient air (oxygen).
These unburnt carbon particles become white hot and produce light. Thus the white-hot carbon particles are responsible for the luminous nature of the flame. They later form black soot which makes the apparatus dirty (Sooty flame).
A luminous flame has four zones namely:
1. The blue region 2. Almost colourless region
3. Yellow region 4. Thin outer region
When the air hole is open, a lot of air enters the chimney and mixes with the laboratory gas. The mixture burns more quickly and completely. The flame given out is pale-blue and is called a non-luminous flame. This is because it does not give out much light. Sometimes it is not easily noticeable. Non-luminous flames are usually very hot. They do not give off smoke i.e. is non sooty hence it is the most preferred flame for heating in the laboratory
Heating effects of luminous and non-luminous flames
Expected response
Water heated using the luminous flame takes longer to boil as compared to that heated with the non-lumionous flame. The bottom of the beaker heated with the luminous flame appear black (has soot) while the beaker heated using the non-luminous flame is clean (has no soot).
The facts
A non-luminous flame is hotter than a luminous flame. It also doesn’t produce soot that would blacken the apparatus. The luminous flame on the other hand produces less heat. It also produces soot that blackens the apparatus. The non-luminous flame is hence normally preferred for heating in the laboratory. Luminous flames such as that of a candle flame or lantern lamps are used for lighting
Other common apparatus
Tubes-There are different kinds of test tubes for different uses.
a) Ignition tubes are used for decomposition of compounds.
b) Ordinary test tubes are used for heating substances.
c) Boiling tubes are used for boiling small amounts of liquids. Beakers-Are vessels made of plastic or glass. There are beakers of varying capacities.
Beakers are used as containers for holding liquids and sometimes for boiling liquids. Beakers used for boiling purposes are made of either glass, pyrex or borosilicate.
Flask - They are used as containers for holding, mixing and sometimes heating solutions.
Activity
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