tailieunhanh - Đề thi Đại học môn Tiếng Anh khối A1 năm 2014 (Mã đề 973)

Đề thi Đại học môn Tiếng Anh khối A1 năm 2014 (Mã đề 973) đề chính thức từ Bộ giáo dục và Đào tạo, cấu trúc gồm 80 câu hỏi với hình thức trắc nghiệm có thời gian làm bài trong vòng 90 phút. và thử sức mình với đề thi này nhé. | BỘ GIÁO DỤC VÀ ĐÀO TẠO ĐỀ CHÍNH THỨC Đề có 6 trang ĐỀ THI TUYỂN SINH ĐẠI HỌC NĂM 2014 Môn TIẾNG ANH Khối A1 Thời gian làm bài 90 phút không kể thời gian phát đề Mã đề thi 973 Họ tên thí sinh . Số báo danh . ĐỀ THI GỒM 80 CÂU TỪ QUESTION 1 ĐẾN QUESTION 80 Read the following passage and mark the letter A B C or D on your answer sheet to indicate the correct answer to each of the questions from 1 to 10. The ability to conduct electricity is one of the key properties of a metal. Other solid materials such as silicon can conduct electricity but only effectively at certain temperatures. Also some substances such as salt sodium chloride can conduct when molten or when dissolved in water. The ability of metals to conduct electricity is due to how their atoms bond together. In order to bond together the metal atoms lose at least one of their outermost electrons. This leaves the metal atoms with a positive charge and they are now strictly ions. The lost electrons are free to move in what is known as a sea of electrons. Since the electrons are negatively charged they attract the ions and this is what keeps the structure together. An electric current is a flow of charge and since the electrons in the sea of electrons are free to move they can be made to flow in one direction when a source of electrical energy such as a battery is connected to the metal. Hence we have an electric current flowing through the wire and this is what makes metals such good conductors of electricity. The only other common solid conducting material that pencil users are likely to encounter is graphite what the lead of a pencil is made from . Graphite is a form of carbon and again the carbon atoms bond in such a way that there is a sea of electrons that can be made to flow as an electric current. Likewise if we have an ionic substance like salt we can make the electrically charged ions flow to create a current but only when those ions are free to move either when the substance is a liquid or dissolved