Dr Peter Wothers says the word 'chemicals' is being misused to mean something harmful or unnatural

The scientist who will give this year's Royal Institution Christmas lectures has hit out at misuse of the word "chemicals" to mean something harmful or unnatural.

"It does annoy me," Dr Peter Wothers, a teaching fellow in chemistry at the University of Cambridge, told the Guardian. "There is one food chain which says that 'there are no obscure chemicals in our food'. I thought, how ridiculous."

In a cup of coffee, said Wothers, more than 2,000 different compounds have been identified and there are thousands of others that are yet to be identified. "Yes they're obscure, get over it, this is life and we are just a big bag of chemicals."

Wothers will challenge the suspicion directed at chemistry in this year's three Christmas lectures, entitled The Modern Alchemist. Each lecture will be based on an ancient Greek element – air, water and earth. The fourth element, fire, will feature throughout the series in the form of explosions and daring demonstrations.

The Royal Institution's Christmas lectures were initiated by Michael Faraday in 1825 to bring science to young people. They have run every year since – except during the second world war – and lecturers have included Sir David Attenborough, Prof Richard Dawkins, Dame Nancy Rothwell and Prof Monica Grady.

Wothers said he wanted the audience to leave understanding that chemistry was how we all interact with the world. "Ultimately, our whole world is made up of molecules combined together, we are chemicals. When you make a cup of tea, you're doing chemistry. You are extracting things that you want from things that you don't want. You've done some chemistry – you've made a hot solution, you've filtered it and extracted what you want – that is what a chemist does."

In the "air" lecture, Wothers goes back to the beginnings of modern chemistry in the 17th and 18th centuries, when early scientists such as Joseph Priestley, Henry Cavendish and Antoine Lavoisier were working out and measuring the composition of the atmosphere.

Lavoisier, often called the father of modern chemistry, was the first person to fully explain what was happening during combustion, for example.

"There was the phlogiston idea, things burned because they contained this flammable 'principle' and it makes sense because you can see something is coming out when a block of wood burns," said Wothers. "But there were problems when metals burned in air because they got heavier. How do you explain that if the metal is meant to contain this phlogiston and it's losing that as it's burning, and yet it's getting heavier? Lavoisier was the first to understand the role of oxygen and say that there is something in the air that is combining with the metals and increasing their weight."

In the "water" lecture, Wothers examines its importance on Earth and explores the options for turning it into a sustainable fuel source for the future – scientists are looking at ways of developing catalysts to help split water into its component parts in order to subsequently use the hydrogen in fuel cells and engines.

In the final lecture, "earth", Wothers reveals what is under our feet and how humans have come up with ways, over history, to extract the valuable resources. "Copper is relatively easy to extract from its ores but iron is much harder to extract, so the iron age follows the bronze age. But there are more recent elements being extracted from the Earth, one of the most notable being silicon."

Wothers said he got enthused by chemistry at the age of eight. "As soon as I got into secondary school, they realised they couldn't keep up with my thirst for the subject. I got a job working for a laboratory suppliers and they used to pay me in chemicals and equipment – I had a stunning lab at home with centrifuges, bunsen burners and balances."

This year's lectures would be a welcome return to a subject that had been skipped over in recent years, said Wothers. "There hasn't been a lot of chemistry for quite some time now and, yet, the first lecture Michael Faraday gave was just titled "chemistry"."

• The Royal Institution Christmas lectures are being shown on BBC Four. You can hear an interview with Dr Peter Wothers on the Guardian's Science Weekly podcast.