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
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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 in
water. In its solid state an ionic substance like salt cannot conduct electricity as its charged ions cannot flow.
Electrical insulators are substances that cannot conduct electricity well either, because they contain no
charged particles or any charged particles
they might contain do not flow easily. Water itself is a poor
conductor of electricity as it does not contain a significant amount of fully charged particles (the ends of a water
molecule are partly charged but overall the molecule is neutral). However, most water we encounter does
contain dissolved charged particles, so it will be more conductive than pure water. Many of the problems that
occur when touching electrical devices with wet hands result from the ever-present salt that is left on our skin
through perspiration and it dissolves in the water to make it more conductive.
By
Helena Gillespie and Rob Gillespie.
Science for Primary School Teachers.
OUP
Question 1: Electrical conductivity is ______.
A. one of the key properties of most solid materials
B. impossible for any substance when it is dissolved in water
C. completely impossible for silicon
D. one of the most important properties of metals
Question 2: According to the passage, a metal can conduct electricity due to ______.
A. the way its atoms bond together
B. the absence of free electrons
C. its atoms with a positive charge
D. the loss of one electron in the core of its atoms
Question 3: The word “
outermost” in paragraph 1 mostly means ______.
A. nearest to the inside
B. the heaviest
C. furthest from the inside
D. the lightest
Question 4: The atoms of a metal can bond together because ______.
A. they lose all of their electrons
B. negatively charged electrons attract positive ions
C. the lost electrons cannot move freely in the sea of electrons
D. electrons can flow in a single direction
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