TOPIC 4: SCIENTIFIC PROCEDURES | CHEMISTRY FORM 1

The
first step of the scientific procedure is to identify a researchable
problem. A problem is an obstacle that makes it difficult to achieve a
desired goal, objective or purpose. It refers to a situation, condition
or issue that is unresolved. Observation refers to identification of a
chemical phenomenon. This may include observing the colour, smell,
texture of a substance, and so on. Observing involves the use of senses
to obtain information. Observation is more than the bare fact of
observing. It is determined by use of five senses namely, smell, touch,
taste, vision and hearing. For example, to identify the colour of a
substance you have to see it with your eyes. The same case applies to
detection of the smell of a substance or gas produced by reacting
substances in a laboratory. To be able to detect the smell of a gas you
have to use your nose to smell it.

Observation
helps a scientist to identify a problem. Observation may involve making
measurements and collecting data. The data may be descriptive
(qualitative) or numerical (quantitative) in nature. Numerical
information such as the fact that a sample of sulphur powder measures
50g is quantitative. Non-numerical information, such as the fact that
the colour of anhydrous copper (II) sulphate is white, is qualitative.

Once
you identify a problem, it becomes easy to state it scientifically. For
example, you can observe that when you put a given volume of water in a
narrow container and expose it to open air, it takes much longer to
evaporate and decrease in volume. However, when you put the same amount
of water in a wide container, it takes a much shorter time to do so.
This phenomenon can be investigated scientifically.

After
identifying and stating the problem, you can formulate a testable
hypothesis for that problem. A hypothesis is a statement. It is a
prediction or proposed solution to a problem based on prior knowledge or
known information about a chemical phenomenon. It is a logical guess
about the outcome of the experiment. A hypothesis must be able to be
tested. Therefore, a hypothesis can be described as a tentative
explanation for an observation, phenomenon, or scientific problem that
can be tested by further investigation. It can be rejected, modified, or
accepted only after conducting an experiment to prove or disprove it.

Let
us take an example of water at the previous stage. It was observed that
the water held in a wide container evaporated faster than that in a
narrow container. Based on what we know about evaporation (prior
knowledge) we can formulate a hypothesis pertaining to this phenomenon.
It is well known that one of the factors affecting the rate of
evaporation is the surface area. From this fact, we can formulate a
testable hypothesis which states that “evaporation of water increases with increase in surface area of the container in which that water is placed”.
This is just a statement. It can be proved wrong or correct by setting
up and doing an experiment. Remember that this is just an example,
though not very much related to chemistry. We can turn to another
relevant example as well.

Now,
let us look at an example of anhydrous copper (II) sulphate. The
anhydrous salt is in powder form. When you expose this salt to open air,
it changes its colour and shape, from its original white powder to blue
crystals. Why does this happen? From our knowledge of the properties of
this salt (prior knowledge or information gathered) when it is placed
in open air, it absorbs water vapour from the air. It is this water
vapour which it absorbs that turns it blue. We can go as far as
formulating a hypothesis, which states that “When white anhydrous
copper (II) sulphate powder is exposed to open air, it absorbs water
vapour from the air and turns into blue crystals”.
We still have a doubt about this hypothesis. How do we know that the
liquid absorbed by the salt is really water? To accept or reject this
hypothesis, we must conduct an experiment.

After
making a hypothesis, the next step is to plan and conduct an
experiment. Planning an experiment involves writing down steps for an
experiment that will answer the question. It should be remembered that
experimental plan should include short and clear steps. It should also
include the materials and methods that will be used in the experiment.
These may include safety gears such as goggles, gumboots, gloves, etc.
It must also state all expected hazards to be accompanied with the
reacting substances or chemical phenomena being experimented. This could
either occur as a result of mishandling chemicals or apparatus,
improper experimental procedure or even testing the products obtained
from the experiment.

In
the scientific method, an experiment is a set of observations
(qualitative or quantitative) made in the context of solving a
particular problem or question. An experiment is conducted in order to
retain or falsify a hypothesis concerning a particular phenomenon. The
experiment is a basis in the practical approach to acquiring deeper
knowledge about the chemical world.

Experimenting
involves carrying out a procedure under controlled conditions in order
to make observations and collect data. To learn more about matter,
chemists study systems. A system is a specific portion of matter in a
given region or space that has been selected for study during an
experiment or observation. When you observe a reaction in a test tube,
the test tube and its contents form a system.

Your
experiment tests whether your hypothesis is true or false. It is
important for your experiment to be a fair test. You conduct a fair test
by making sure that you change only one factor at a time while keeping
all other conditions the same (constant). These factors are also called
variables. They are the factors that affect the problem you want to
investigate. They can change or be changed during the experiment. Such
factors include temperature, volume, speed, light, concentration, light,
etc.

There are three types of variables. These are:

For
example, you might be interested to carry out an experiment to
determine the influence of the concentration of phosphorus fertilizer on
maize growth. To get the best results, you grow maize in similar
conditions of soil and atmospheric environment (controlled variable) but vary the quantity of fertilizer in each test (independent variable). Then you measure the height of maize plants (dependent valuable)
after a certain interval of time as shown in figure below. The value of
the height you will obtain will obviously depend on the amount
(concentration) of the fertilizer applied. This is a typical fair test.
However, most chemistry experiments do not involve fair tests.

Now,
let us turn back to our experiment. In the example of determining
whether the surface area increases the rate of evaporation or not, we
can design an experiment to prove or disprove this phenomenon. This is
conducted by filling a basin (with large surface area) and a bucket
(with small surface area) with 10 litres of water each. Then the two
containers are placed in open air for 3 days. Here, care must be taken
to place both containers under similar environmental conditions.
Containers must be of the same type, that is, both must be plastics,
metals, etc. In addition, the water used must be obtained from the same
source.

The
only variable to be kept constant is the volume of water, which is set
to the volume of 10 litres. You should repeat your experiment several
times to make sure that the first results were not just an accident.

Observation
and recording of data must be done from the beginning to the end of the
experiment. Data is the information gathered during the experiment.
This can include descriptive (qualitative) and numerical (quantitative)
data. Numerical data is that which can be measured, for example, 10
litres of water, 5g of copper, a five centimetre long ribbon of
magnesium, etc. Qualitative data include information that cannot be
measured, e.g. colour, shape or appearance, smell, feel, etc. Recording
data is an important part of the scientific method because it helps
scientists organize their ideas and observations. Charts, graphs, lists,
diagrams, tables and even sketches are all the ways of recording data
during experiments. Records appearing in the form of tables are easy to
read, understand and interpret.

Continuing
with our hypothetical experiment for determining the effect of surface
area on the rate of evaporation, we expect that at the end of the
experiment the volume of water in each container will have dropped to a
certain extent.

We
also expect that the volume of water lost from the basin will be bigger
than that lost from the bucket. This means that more water will
evaporate from the basin than from the bucket. Considering that
scenario, we can then predict what the data can be like. Let us take
this model as a real experiment and assume the kind of results that
could be observed and collected during the experiment.

After
3 days of the experiment, water from each container was measured. The
results obtained were summarized in the following table.

Once
your experiment is complete and after you have collected data, you
analyse your data to see if your hypothesis is true or false. In table
4.1, we find that, at the end of the experiment, 3 litres of water had
evaporated off from the basin as compared to 1.5 litres from the bucket.
What does this data tell us? What is it trying to reveal? This means
that from the basin (with large surface area) water evaporated faster
than that from the bucket (with small surface area). The data reveals
the fact that surface area plays a major role in evaporation of water
and many other liquid substances.

However,
you may sometimes get unexpected results. You may find that your
hypothesis was false. In such a case, you will construct a new
hypothesis and start the entire process of the scientific method over
again. Even if you find that your hypothesis was true, you may want to
test it again in a new way.

The
last stage (at this level of study) of the scientific method is to make
inferences and draw a conclusion. Scientists look at the information
they gathered and observed. Then they make connections to draw a
conclusion. These conclusions may be or may not be in agreement with
their predictions. Scientists make incorrect predictions all the time.
An important part of the scientific process is to understand why
predictions were incorrect. Many scientists will repeat an experiment
several times to see if they can replicate the results before
concluding. This ensures that they have conducted the experiment the
same way each time and make sure no introduced errors or outside factors
affected the experiment’s outcome.

Based
on data in a hypothetical experiment above, we found that 3.0 litres of
water evaporated from the basin (a container with wide mouth and hence a
large surface area). At the same time, 1.5 litres of water evaporated
from a bucket (a container with a narrow mouth and hence a small surface
area). From this result, of course, we can conclude that evaporation of water increases with increase in surface area of the container in which that water is kept.
Therefore, our hypothesis is proved true and correct. Remember always
to base your conclusion on the collected and analysed data, though it
may deviate, to some extent, from the reality for one reason or another.