Leaving Cert chemistry: higher and ordinary level:Former Russian security agent Alexander Litvinenko, who died of radiation poisoning late last year, featured in both higher and ordinary papers yesterday.

With the issues of greenhouse gases and oil refining also featuring, a clear effort was made to make chemistry more topical and relevant to students' lives.

William Hehir, a teacher in St Andrew's College, Booterstown, Dublin, and subject expert for examsupport.ie, praised this contextual link. "I liked the idea of linking a radiation question in with the Litvinenko story," he said, adding that such connections made topics more engaging for students.

"Challenging enough" was the verdict of Tara Lyons, a chemistry teacher at the Institute of Education, on the higher paper. However, she said the questions that were asked year after year also came up this year. "The stalwarts were present, and I think most students would have found eight questions to suit them."

Mr Hehir welcomed the fact that there was less of an emphasis on knowing definitions that students could learn by rote, and more questions that required them to apply their knowledge.

One unusual part of a question about the elements needed to cause a dust explosion may have thrown some students initially but they had the knowledge for the right answer, according to Mr Hehir. "It was just about applying what they knew to the question."

There was quite an overlap in question topics between the ordinary and higher papers, according to Ms Lyons.

"Radiation was asked on both higher and ordinary level, for example," she said, noting that the effort to contextualise chemistry had been made in both papers.

Chemistry is the least popular of the three main science subjects, with just over 7,000 students sitting the papers yesterday. The overwhelming majority of those sat the higher exam. According to teachers, students were happy coming out of the exam, with many having time to do an extra question on top of the eight required.

Overall, the papers were praised as being challenging but positive for a time when science is becoming more important for the Irish economy but less popular as a subject.

"It was a positive paper, and one that will keep students doing chemistry, I think," said Mr Hehir.