Lesson Video: Health and Safety in Experiments Physics

In this video, we learn how to use the terms risk, hazard, and severity to describe the dangers involved in conducting scientific experiments.


Video Transcript

Science experiments can often be dangerous, from dealing with corrosive chemicals in the chemistry lab to working with some deadly virus in the biology lab to handling radioactive substances in the physics lab. Hazards can be found everywhere in the world of science. Therefore, it is vital that every experimentalist is versed in how to minimize the chances of anything go wrong.

In this video, we will discuss the meanings of the terms hazard, hazard severity, and risk. Now, in everyday language, we often use the words hazard and risk interchangeably. However, they actually mean subtly different things. So let’s have a look at their definitions.

According to the Canadian Centre for Occupational Health and Safety, a hazard is defined as a potential source of damage, harm, or adverse health effects on something or someone. In other words, a hazard is an object or an event or anything else that could cause potential damage. We’ve actually already mentioned a few hazards in this video earlier on.

Corrosive chemicals often found in a chemistry lab are an example of a hazard, so are microbes or microorganisms that could be potentially dangerous to human health grown on Agar plates and so are radioactive materials commonly found in physics labs. So these are all types of hazard. But even things that you don’t expect to be hazards can be hazards, for example, a set of stairs. Stairs are hazard because you can trip over them and injure yourself. So even the most mundane things can potentially be hazards.

Now we’ve thought about what the word hazard means, so let’s now think about hazards severity. Hazard severity is basically a measure of how adverse or how bad the effects of a hazard can be. So for example, coming back to our radioactive substance, there can be very negative effects such as radiation sickness or even genetic mutation or contamination of the surrounding environment with radioactive materials. And so, the severity of this hazard is quite high.

Now if we compare this to our set of stairs, then the stairs also have a relatively high hazard severity, especially when going down the stairs. Because if somebody was to trip over on these stairs whilst going down, it is possible that they could fall down the entire flight of stairs and maybe break some bones and in the worst-case scenario actually die. Later on in the video, we’ll see examples of hazards which have relatively low severity.

But for now, let’s look at another definition. The word “risk” is used to describe the likelihood or probability of an adverse or bad outcome due to a given hazard. Now, this depends on a couple of things, firstly, what the hazard itself is. So for example, if we come back to our radioactive substance, we’ll see that if we don’t take the proper precautions, then the likelihood of something going wrong is quite high because a radioactive substance will release ionizing radiation which will often do damage to a living organism such as via genetic mutation. And so, handling something like a radioactive substance can be a fairly high-risk process.

However, risk does not just depend on what the hazard actually is, it also depends on the exposure to a hazard. For example, if we take the proper precautions such as by encasing the radioactive substance in very thick lead, then our exposure to this radioactive substance is reduced. Equivalently, a block of radioactive material on the other side of the world is not going to do any damage to us because we aren’t exposed to it. Therefore, the exposure to a hazard is equally important when assessing the risk of a hazard.

Perhaps, a better example of this is when we consider corrosive chemicals in a chemistry lab. If we wear gloves and carry the corrosive chemical in a tightly sealed container, then the risk of something going wrong is much lower because we’re not exposed to that chemical. Conversely, if we carry in an open container whilst running around the lab and the container is nearly overflowing and we’re not wearing gloves, then the risk is much higher.

So these three terms that we’ve just learnt about are important to think about when designing an experiment. We need to ensure that the experiment is conducted in a safe manner as possible, safe not just for humans, but for any wildlife around the humans as well as any property and even the environment surrounding the experiment. Let’s now take a look at a few examples of these terms in action.

Which of the points of the graph of risk and hazard severity best corresponds to the activity of measuring the temperature of water being boiled in a beaker that is heated over a Bunsen burner?

Okay, so in this question, we’ve been told that we’ve got a beaker of water. And this beaker is heated with a Bunsen burner until the water is boiling. Now, we’re trying to measure the temperature of this water. So we need to stick a thermometer in the water as well. Now, let’s start by identifying the hazards in the setup.

Well, first of all, we’ve got boiling water which could be spilled and that is a hazard. And secondly, we’ve got a Bunsen burner which is switched on; that’s also a hazard. So these are the two hazards in our setup. Now of course, there are more. But these two are the main ones.

So let’s now think about the hazard’s severity. In other words, if things were to go horribly wrong, how bad would it be? Well, if somebody was to first of all put their hand close to the Bunsen burner, then they would get potentially burned by it and that is actually really severe. And as well as this, because we’re dealing with boiling water, that could potentially be spilled resulting in scalds and yet more burning. So for the hazard severity, we can say that due to the possibility of scalding and burning, the severity is high.

And finally, let’s think about the risk. Now, risk is to do with the estimated probability of something going wrong: how likely is it that something bad will happen? Well in this situation, if we’ve got a beaker of water that’s boiling on a Bunsen burner, assuming that everything else has been set up correctly, such as the tripod on which the beaker is balancing, then the only thing that the experiment has to do in order to measure the temperature is to put the thermometer into the beaker of water.

Now they can do this when the water is boiling which is slightly dangerous or they could have done this before the water was even boiling, even before the Bunsen burner was switched on. Therefore, it’s likely that the order in which the scientist set up this experiment is that they fill the beaker with water, put the thermometer into the beaker, set up the tripod and the beaker on top of it, and only then switch on the Bunsen burner. Once all of that is done, the only thing that the scientist has to do is to read the temperature on the thermometer.

This means that they don’t have to touch the setup whilst the water is boiling. And hence, the likelihood of anything getting knocked over or them touching the Bunsen burner is really low. They’re basically not exposing themselves to the hazard: neither the boiling water, nor the Bunsen burner. The only thing they’re doing is looking at the thermometer from far away. And hence, the risk can be said to be low because of the low exposure to the hazards.

So let’s now look at this graph that we’ve been given at the question. On the vertical axis, we’ve got increasing hazard severity as we go up. And on the horizontal axis, we’ve got increasing risk as we go across. So for this science experiment, we’ve said that the severity is high and the risk is low. That means that we’re looking for a point that is high up on the hazard severity axis, but low down on the risk axis.

We can draw dotted lines across and up from both of these points on the two axes and see that the point at the intersection of these two dotted lines is point 𝐴. In other words, point 𝐴 is the one which shows high hazard severity, but low risk. And so, our answer to this question is that point 𝐴 corresponds to the activity of measuring the temperature of water being boiled in a beaker that is heated over a Bunsen burner.

Okay, let’s look at another similar example: which of the points on the graph of risk and hazard severity best corresponds to the activity of measuring the weight of a cup of water that is filled to the brim by a high-speed flow of water?

Okay, so in this question, we’ve got a cup that is filled to the brim with water by a very high-speed flow of water. We’re trying to measure the weight of the water which we can do by measuring its mass first and remembering that the weight of an object is found by multiplying the mass of that object by the acceleration due to gravity on Earth 𝑔. So we can place this cup on a weighing scale.

In order to answer this question, what we need to do is to assess the risk and the hazard severity of this entire experimental setup. So let’s start by considering the hazards in this experiment. Well, one potential hazard is the water itself. It could get everything wet for example. And in this experiment, it seems to be the main hazard.

So let’s think about the hazard severity. The hazard severity is how bad the effects would be if something were to go wrong and in this case if the water went everywhere, such as for example on the hands of the scientist doing this experiment or on the mass balance or on the books that the scientists is using to record the results of this experiment. Then, the water will make everything wet.

However, this is not a particularly severe situation. All that will happen is a few things get wet and nothing more. There’s nothing corrosive or dangerous or explosive or harmful or damaging. And so, we can say that the severity of the hazard in this experiment is low.

Finally, let’s consider risk. Now, risk is talking about the likelihood or probability of something going wrong or in other words the probability of the hazard being allowed to actually be hazardous. Well, in this question, we’ve been told that a high-speed flow of water is filling the cup and the cup is filled to the brim.

This means that it’s very likely that the water will overflow because it’s difficult to control the water and ensure that it fills the cup up to the brim without overflowing especially because it’s a high-speed flow of water. So the risk is actually quite high in the situation even though the severity is low. In other words, the probability of something going wrong is high. But the damage that that thing going wrong will do is low.

So looking at our graph now, we’ve got a graph of hazard severity on the vertical axis and risk on the horizontal axis. We want to find the point of the graph that is high risk, but low severity. So let’s move along the risk axis and go to a higher risk position and move up the hazard severity axis but only a little bit because we want a low hazard severity. So we can then draw a dotted line across from the hazard severity axis and up from the risk axis.

The point that intersects both of these two lines is point 𝐸. And hence, that is the answer to our question. The point on the graph that corresponds to the activity of measuring the weight of a cup of water that is filled to the brim by a high-speed flow of water is point 𝐸.

Alright now, let’s summarize what we’ve learnt in this lesson. In this video, we defined a hazard as a potential source of damage, harm, or adverse health effects on something or someone. As well as this, we saw that hazard severity is related to help adverse the effects of a hazard can be. Thirdly, we saw that risk is defined as the likelihood or probability of an adverse outcome due to a given hazard. And finally, we looked at hazard severity against risk graphs which can be very useful when planning an experiment and insuring that it’s as safe as possible.

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