Chemical Analysis

Definition of chemical analysis

Is it possible to identify the presence of urine in a pool just by looking at it? No! Likewise, we cannot see the toxic products that urine produces on reacting with chlorine. To identify them in the pool water, we use chemical analysis.

There are different types of chemical analysis, as well as various common techniques and methods. But before we jump into them, let us have a brief look at the steps of chemical analysis.

Steps of chemical analysis

No matter the method or technique used, chemical analysis typically involves the following steps:

1. Collecting a sample of interest.
2. Picking an appropriate analytical method to analyse the sample.
3. Prepping the sample.
4. Analysing the sample using your chosen method, test, or technique.
5. Interpreting the results of the analysis. This might involve calculations or further tests.

These steps give us a brief overview of how chemical analysis is done. Each step might have further sub-steps and include unique analytical procedures. The choice of analytical techniques or methods used depends on our sample and the type of chemical analysis we want to carry out. Let's explore the types of chemical analysis now.

Types of chemical analysis: qualitative and quantitative

Chemical analysis is classified into two major types

• Qualitative chemical analysis.
• Quantitative chemical analysis.

We'll first have a look into qualitative chemical analysis.

Qualitative chemical analysis

You taste a pizza and might feel it is too hot for your taste. What makes the pizza so spicy? Maybe it is topped with jalapeños, or perhaps pepperoni? These toppings help give the pizza its unique taste and identity.

Fig. 1: Supreme pizza.

Therefore, to determine why a pizza tastes a certain way, we try to identify what it is topped with. This is a kind of qualitative analysis.

Just like the toppings of a pizza, all the chemical samples have different constituents within them. To determine the constituents of a chemical sample, we use qualitative chemical analysis. It tells us exactly which chemical species the sample is made from, be it different molecules, elements, or compounds.

Quantitative chemical analysis

Let us consider the example of pizza again. We know that the toppings like jalapeños and pepperoni make a pizza taste hot. But how do we know how much pepperoni is added to a pizza? This question is how much of something is answered by quantitative chemical analysis.

Why might quantitative chemistry be useful? Well, what if you like a little bit of heat on your pizza, but not too much? You'd probably prefer a pizza topped with just a few slices of pepperoni. Knowing exactly how much pepperoni will be in your meal allows you to pick the perfect pizza for you.

In short, qualitative analysis deals with what is present in a sample, while quantitative analysis answers how much of the substance is there.

Chemical analysis: tests, methods, and techniques

For your GCSE exam, you need to know about different techniques, tests, and methods used in chemical analysis. You should be able to compare them as well as discuss why you might choose one approach over another. Here is an introduction to chemical analytical techniques:

• Testing for pure substances using melting and boiling points.

• Testing for gases using simple test tube reactions.

• Testing for ions using reactions that you can carry out in class, such as flame tests, the sodium hydroxide test, and tests for anions.

• Instrumental analysis, such as chromatography and flame emission spectroscopy.

Fig. 2: A diagram showing the colours of flames produced by different ions, an example of qualitative analysis.

Instrumental analysis

The tests for gases and the sodium hydroxide test are all simple reactions that you can try out in class. They are quick and convenient to use, but they are qualitative, not quantitative. If we want a quantitative measure of the sample, we have to use certain analytical instruments. They not only identify components of a sample, but also measure their relative amounts. Using analytical instruments in chemical analysis is called (no surprises here) instrumental analysis.

Instrumental methods have certain advantages over test tube reactions. As mentioned above, some are both qualitative and quantitative, whilst most are extremely accurate, sensitive and rapid. In addition, they can work with small samples and are highly versatile.

Examples of chemical analysis

Every household product, from toiletries like shampoo and soap to food products like table salt, sugar, and sauces, is chemically analysed before it reaches you to ensure that it is non-toxic, stable, and safe to use. Given below are a few examples of the fields in which chemical analysis is used and some of its uses that you might encounter.