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Trang 25 mixture, an element, and a compound?✓A mixture is a combination of two or more substances in which the substance retain their distinct identities.✓An element is a substance that
UNIT UNIT ` I- Conversation partice UNIT Give the definition of chemistry? → Chemistry is the study of matter and the changes in undergoes UNIT Why is chemistry often called the central science? → Because a basic knowledge of chemistry is essential for students of biology, physics, geology, ecology, and many other subjects UNIT When did modern chemistry begin? → Modern chemistry start in the nineteenth century UNIT Explain the role of technological advances in chemical studying? →The technological advances enable scientists to break down substances into ever smaller components and consequently to explain many of their physical and chemical characteristics UNIT What can you tell about the future of chemistry? → Chemistry will continue to play a pivotal role in all areas of science and technology UNIT 6 Give three major advances have enabled us to prevent and treat diseases? →They are public health measures, surgery with anesthesia, and the introduction of vaccines and antibiotics UNIT Why the knowledge of chemistry important in treatment of disease and in the pharmaceutical industry? → Chemist in the pharmaceutical industry are researching potent drugs with few or no side effects to treat cancer, AIDS, and many other diseases UNIT What are the major and potential sources of energy in the twenty first century? → The major and potentials sources of energy are fossil fuels, nuclear fission, and solar energy