And here,” says Jiffty Chug, beaming, “is my lab, my favourite room in the whole school. It just speaks chemistry.” Mrs Chug beams a lot. Runner-up in the Salters’ Science Teacher of the Year award, head of science at Copthall Girls school in Barnet, she is, says headteacher Lynn Gadd, “magical in the classroom”. What has made her so special?

Copthall has 1,100 pupils aged 11-18, 70 per cent of whom gain five or more A*-C grades at GCSE. It is an oversubscribed neighbourhood comprehensive in a borough with a large number of selective schools. A-level chemistry and biology are popular, with 40 and more taking each subject.

One of those teachers always to be found behind the scenes in school productions, serving teas at shows, accompanying school trips - “We had such a wonderful time in Cornwall at the millennium” - running a science club, mentoring newly qualified teachers, on the board of governors, liaising with local primary schools, Jiffty Chug is never happier than in her lab sharing chemistry with a class of rapt pupils. As sixth-former Reepul puts it: “When she explains something, it’s in your head.” Mrs Chug herself sees it slightly differently: “The pupils here really get involved and they’re grateful for learning.”

On a typical lesson one bright spring day, she can be seen in action. She says: “I’ve got to be cheerful the whole time and the children thrive on that.” As she dons her white coat - a leaving present from last year’s sixth form, stencilled with molecular patterns - the smiles in the classroom mirror her own. She goes on: “Treat every child the same initially and develop them as people.” As she plans the sixth-form lesson on alkanes, alkenes and arenes, she deals with a question on homolytic fission and heterolytic fission: “We’ll think about that as we go through and I think you’ll find there is a pattern.” Some of the girls are confident - “born chemists” as she says - but others are puzzled. Thisis healthy, says Mrs Chug. When discussing concepts, she is careful to bounce questions between the weaker and stronger members of the class, so that the most able get to ponder how a general truth might be derived while slower pupils can talk through a set of experiment results. No one is left out, no one fidgets. Lynn Gadd remarks: “She makes them feel comfortable but challenged.”

The pupils are equally enthusiastic. Says Renukha: “The lessons are enjoyable. The work is intense but, because the lessons are fun, you concentrate.” Shaking a test-tube, Shireen adds: “She’s going to go over it 200 times if you need it - breaktimes, lunchtimes, she doesn’t mind.” Karen joins in: “She just makes us understand.”

“Ladies,” says Jiffty Chug quietly, “you didn’t all get the correct results, so shall we look at the CD-Rom?” As they gather round the computer, she remarks that dealing with sixth-formers is quite a skill. “It’s no good to be a bossy boot. You have to communicate on their level.” When the class turn their attention to the final exposition of the day on differences between carbon-bonded molecules, she mixes straight exposition:

“Water is a polar substitute and causes heterolytic fission in bromine”, with an explanation of method: “Can you see what I’m doing? I’m getting you to think about that chemical reaction and what is happening and what mechanism.”

Mrs Gadd comments: “She makes young women believe they can do science.”

As well as commitment to the pupils, Jiffty believes that a good teacher needs commitment to the subject. “I had the most wonderful chemistry teacher myself. I just loved it and it never seemed hard. And when I am teaching chemistry, the time seems to fly. The girls say: ‘That went fast, Mrs Chug.’ And I am myself amazed how fast the time went.”

The winner of this year’s Salters’ Prize for Teaching Chemistry is Charles Lees, head of chemistry at Wallace High School, Stirling.The Salters Institute, Salters’ Hall, Fore Street, London EC2Y 5DE. Tel: 020 7588 5216