Text lesson

Unit 1 — Chemical Reactions and Their Environmental Impacts

Science — Third Preparatory

3.3 What tobacco contains

Comparison aspect	Main idea	Example	Keywords
Nicotine.	A natural organic compound containing carbon hydrogen and nitrogen with an alkaline nature. Heat from the burning cigarette vaporises nicotine and the smoker inhales it with the smoke. Nicotine is the substance that causes addiction	—	naturalorganiccompoundcontaining
Carbohydrates and proteins	(sugars plant proteins and fibres). When burned especially incompletely they produce carbon monoxide and tar a thick sticky dark liquid made of the combustion products of these compounds	—	sugarsplantfibresburned
Mineral elements.	Potassium magnesium and calcium (harmless as minerals) but also toxic heavy elements	cadmium lead and arsenic	Potassiummagnesiumcalciumharmless
Radioactive elements.	Small amounts	polonium-210 which can damage the lungs by radiation	Smallamountsexamplepolonium

toxic gases carbon monoxide (CO) and hydrogen cyanide (HCN);
irritant gases nitrogen oxides (NO, NO₂) and ammonia (NH₃).
A burning cigarette is therefore not just paper and dry leaves: complex reactions produce several thousand chemicals, many of them toxic or carcinogenic (cancer-causing).
What happens to minerals and radioactive elements?

Key points

Volatilisationsome heavy metals and radioactive elements vaporise when the tobacco ignites and become gases or stick to fine tar particles.

Inhalationthe atoms enter the lungs and deposit in the branches of the bronchi.

Accumulationthe build-up causes damage to the DNA of lung cells, which raises the risk of cancerous tumours.

Ashthe leftover ash contains the non-volatile minerals (calcium, potassium), giving it a white or grey colour.

Unit 1 — Chemical Reactions and Their Environmental Impacts · 21 / 30

3.3 What tobacco contains