Chapter 13: Laboratory and Practical SkillsShort Questions with Answers

Mineral acids including HF (also concentrated H₂SO₄, HCl, HNO₃), caustic alkalies (NaOH, KOH) and glacial acetic acid. They attack skin, eyes and the respiratory tract.

When reactions are not properly performed, reactive chemicals may cause fires and explosions, and may evolve dangerous gases. These can cause extreme damage to life and property: burns, injuries from flying glass, poisoning, damage to the lab.

Asphyxiants: hydrogen cyanide, carbon monoxide, nitrogen, argon, helium, methane and carbon dioxide. N₂, Ar, He, CH₄ and CO₂ push out oxygen; CO and HCN stop the body using oxygen.

To let people know the hazardous nature of the area or chemical, so that every person entering understands and acts accordingly; they indicate that specific precautions must be observed. Symbols are understood at a glance, even without reading.

Drills let students practise the actions to take in an emergency, not just hear about them. In a real emergency people act from practice: they stay calm, know the exits, the extinguisher and shower locations, and leave in order. During drills, fire-fighting and other equipment is also checked to be in working order.

An ordinary refrigerator has sparks inside (thermostat switch, light switch, motor). Vapours of flammable liquids collect in the closed cabinet and can be ignited by a spark, causing an explosion. Only special spark-proof (laboratory-safe) refrigerators may be used.

It is best not to. Vapours and splashes can get trapped behind a lens and damage the eye, and lenses are hard to remove quickly to rinse the eye. If they must be worn, always wear sealed safety goggles over them and tell the teacher.

On sudden shock, friction or impact (dropping, moving the container), on heating or near flames and sparks, and when some of them dry out (picric acid is far more dangerous when dry) or grow old (peroxides).

Acids and bases are first neutralised, then flushed to the sewer with plenty of water. Hazardous waste is sent to a hazardous waste disposal site, never poured straight down the drain.

Take care: there is a possible hazard here which could cause minor or moderate injury if you are careless. It is a lower level than "Danger".

Picric acid, 2,4-dinitrophenylhydrazine, benzoyl peroxide and nitrocellulose.

Compulsory. The book says periodic drills should be held with compulsory participation. An emergency affects everyone, and one untrained person can block exits or panic others.

A place where a student is trained to observe the physical and chemical characteristics of substances by following definite procedures.

If an accident happens, no one would be there to help or call for help. Experiments should be done in the presence of the instructor and lab staff.

Food can pick up traces of toxic or corrosive chemicals from benches and hands and be swallowed.

Never smell directly. Waft the fumes or vapours towards your nose with your hand, from a distance.

Cleaning agents, disinfectants, solvents, paints, compressed gas cylinders, mineral acids and carcinogenic chemicals.

Non-hazardous waste: sewer or trash bin. Acids and bases: neutralised, then sewer. Hazardous waste: transported to a hazardous waste disposal site.

Chemicals or mixtures which have a flashpoint around room temperature: ethers, methylated spirit, benzene, acetone, petrol.

Chemicals that cause a sudden release of pressure, gas and heat when they experience a sudden shock.

Chemicals that attack living tissues when they come in contact with them; solids, liquids or gases that attack skin, eyes, respiratory tract and intestine.

Dilution gives out a lot of heat. Water added to concentrated acid boils at once and spatters hot acid; acid added slowly to water is diluted immediately and the heat spreads safely.

A poisonous material capable of causing serious health problems: mercury, benzene, chlorine, pesticides, ammonia, hydrogen cyanide.

The original container carries the correct name and hazard label, and is made of a material that suits the chemical; transferring it risks spills and mix-ups.

Calcium hydride, sodium, lithium, azides, picric acid, AlCl₃, benzoyl peroxide.

If the reaction becomes violent and the glass breaks, the tape holds the pieces so that flying glass does not injure anyone.

Damage to tissues and organs, vomiting, radiation burns, hair loss and radiation syndrome.

Alpha and beta emitters do extreme damage when inhaled or injected; gamma rays cause external injuries because they pass through the body.

A hazard in which a gas or vapour can cause unconsciousness or death through suffocation. The victim gets no warning of low oxygen.

Rapid breathing, rapid heart rate, nausea and convulsions, then unconsciousness.

A warning sign: a hazard is present (the picture inside shows which: flame, skull, trefoil, corroding hand...).

"Danger" marks the more severe hazards (e.g. highly flammable, risk of asphyxiation); "Warning" marks less severe hazards (e.g. corrosive to skin, harmful).

Mandatory signs: you must do what they show, e.g. lab coats must be worn, wear face mask, wear gloves, sanitise hands here.

A prohibition: do not do this, e.g. "No admittance, authorised personnel only".

Personal protective equipment, made available to students to face emergencies and reduce exposure to hazardous chemicals: lab coat, protective glasses, face shields, apron, boots and hearing protection.

So that a small fire can be controlled quickly before it spreads; in an emergency there is no time to search.

To wash off a large chemical splash on the body or to put out burning clothes.

PASS: Pull the pin, Aim at the base of the fire, Squeeze the handle, Sweep from side to side.