Practical science lessons are being squeezed out by exam pressures on schools, says a science advisory body.
The Council for Science and Technology is writing to the education secretary to warn about the loss of such laboratory experiments.
The advisory body wants experiments to be protected in a shake-up of GCSEs and A-levels in England.
The council says that without practical lessons, science is "like studying literature without reading books".
A Department for Education spokeswoman said: "The Council for Science and Technology rightly notes that our reforms 'will give teachers space and freedom' to conduct more experiments and practicals."
The council, which provides strategic advice to the prime minister, says that cramming for exams is restricting the opportunities for practical learning.
'Essence of science'
This focus on grades is "pushing inspiring practical work into the margins as teachers concentrate on preparing for examinations".
The council's letter to Education Secretary Michael Gove says that rather than being an optional extra, such practical experiments are the "essence of science and should be at the heart of science learning".
The changes to GCSEs and A-levels, including removing the modular structure of exams, should be used as an opportunity for more practical experiments, says the council.
Rather than "repetitive preparation for tests", the council says teachers should be able to "devise innovative and challenging practically based science curricula for their students, including more independent, project-based work".
Accompanying the letter is a report which argues that there has been a "steady erosion" of laboratory skills in school science over the past 20 years.
Prof Jim Iley, executive director of education and science at the Royal Society of Chemistry, said: "We cannot stress strongly enough the importance of developing practical skills in the lab."
A Department for Education spokeswoman said: "By scrapping modules and January assessments, our reforms will end the constant treadmill of exams and leave more time for experiments and practicals in science.
"We have also prioritised experiments in our new curriculum. Pupils will focus on practical work in primary school so they are ready to move on to more advanced laboratory work in secondary school."