Ключевые слова: 13, 15, assembling, atom, atomy, biochemistry, boy, caucasian, chain, chemical, chemistry, child, children, classmate, classroom, corpuscle, experiment, face, girl, girls, kid, kids, laboratory, lesson, measuring, model, molecular, molecule, old, particle, people, physics, plastic, project, reagent, research, school, schoolboy, schoolgirl, science, shape, smile, smiling, student, study, studying, team, teen, teenager, years,