The metal zinc is one of 103 chemical substances found on earth. Chemical elements are basic substances, which
cannot be broken down into other materials.
Zinc
combines easily with many elements, such as oxygen. It also easily combines with other metals,
forming a mixture known as an alloy. The most common alloy is brass, a mixture of zinc and copper.
Pure
zinc is a soft metal with a bright blue and white surface. When exposed to air, its color changes to
gray. A layer of zinc oxide forms on the surface when zinc reacts with oxygen
in the air. This layer of oxide protects the rest of the zinc from oxidation or
rust.
Zinc can be used to cover other metals to prevent
them from rusting. This is probably the most important use of zinc. It is commonly used to protect iron, which
easily rusts and weakens when exposed to air and water. An electrical process
known as galvanizing can protect iron.
During this process, iron is covered with a thin layer of zinc. Galvanizing can prevent iron from rusting for
many years.
Zinc,
therefore, is an extremely useful metal as a protective covering and an alloy.
It is used to make different kinds of objects including door handles, buckets
and batteries. Zinc is also important in manufacturing paint and medicines.
Zinc is also
added to rubber to make it heat resistant
The
underlined word alloy in the passage probably means______________.
a) mixture
b) brass
c) useful metal
d) oxidation
2. The main
idea of Paragraph 4 is :
a) Galvanizing is bad for iron
b) Covering other
metals with zinc protects them from rust
c) Iron is a soft and weak metal
d) Zinc is not important for other
metals
3.When zinc
combines with oxygen ,it_______________.
a) changes into a hard metal
b) rusts and becomes weak
c) turns gray in color
d) becomes blue and white in color
4. When zinc is added to rubber,
it_____________________.
a) turns rubber gray in color
b) becomes white in color
c) makes rubber heat
resistant
d) becomes rusty
5. The
passage is mainly talking about_________________.
a) the importance and
usefulness of zinc
b) zinc, copper and brass
c) protecting iron from rust
d) iron as a commonly used metal
إرسال تعليق