D. Crowley, 2008 Acid & Alkali Hazards

To know the hazards involved when using acids and alkalis Saturday, February 20, 2016

Dangers There are lots of acids and alkalis in the home that are relatively safe, however in the laboratory we sometimes use much more dangerous chemicals… How can you tell which chemicals are safe, and which are dangerous? Hazard symbols are used on bottles (and vehicles) that contain hazardous chemicals – they can be identified by anyone, regardless of language

Dangers Toxic – can cause death is swallowed/inhaled/absorbed by skin etc… Gas under pressure – gas is contained under high pressure Moderate hazard – a substance which may cause harm in some way Oxidising – release oxygen or oxygen containing substance contributing to the combustion of other substances Flammable – catches fire easily Explosive – can explode

Dangers Corrosive – attacks and destroys living tissue Dangerous for the environment – pose an environmental hazard if disposed of incorrectly Health hazards – pose a risk to health, e.g. chemical may cause cancers

Dangers – Old Symbols Toxic – can cause death is swallowed/inhaled/absorbed by skin etc… Irritant – will make skin red or blister Harmful – similar to toxic, but not quite as dangerous Corrosive – attacks and destroys living tissue Highly flammable – catches fire easily

Dangers Hazard symbols show us why the chemical is dangerous… Before we carry out any experiment, we must complete a risk assessment – we need to think about what risks there are, and what we should do if the risk occurs…

Risks Today you are going to carry out an experiment investigating household substances, identifying if it is an acid or alkali, as well as the pH of the substance (using UI) Complete a risk assessment for the practical (consider the risks, how we can minimise them, and what to do if they occur)

Risks Sensible laboratory behaviour as always (no running) Hair tied back No eating, and washing hands after experiment has completed Depending on strength of acid/alkali this could be an irritant/harmful (blistering of skin) or even corrosive (destroys skin) if there is contact Goggles to be on at all times and hands to be washed immediately if acid/alkali touches skin In the event of a spillage do not try to clear it up, instead inform me immediatly

Experiment Test a variety of household substances, identifying if they are an acid or alkali, and what their strength is (pH) - record your results in a table SubstanceAcid or AlkalipH Substance 1 Substance 2 Etc… NeutralStrong acidWeak acidWeak alkaliStrong alkali

Acid & Alkali Examples NeutralStrong acidWeak acidWeak alkaliStrong alkali Stomach acid Skin Lemon juice Fizzy drinks Vinegar Milk Pure water Blood Indigestion tablets Toothpaste Washing powder Oven cleaner

Not hazardous Why is it that lemonade is not considered hazardous, even though it contains lemon juice which has a pH of ~2? Although lemon juice has a low pH it is not concentrated enough in lemonade to make it dangerous – although lemon juice on its own will still sting if it gets in a cut The concentration of lemon juice in lemonade is very low (water has been added to it, which increases the overall pH closer to neutral) which is why we can drink it!