Week 4 – Classifying in Chemistry – Key


Exercise 2.


Organizační diagram

Exercise 3.


1

     Everything around us consists of matter: this paper, your body, the air you breathe, and the
water you drink. Matter is anything that has weight or mass and takes up space.

2


     All matter may be classified as either solid, liquid, or gas. Solids are firm and have a
definite form. Rubber, wood, glass, iron, cotton, and sand are all classified as solids. A
considerable force would be needed to change the shape or volume of an iron bar, for example,
because the atoms or molecules of a solid are densely packed and have very little freedom of
movement.

3






     Solids may be further divided into two classes: crystalline and amorphous. Rocks, wood, paper,
and cotton are crystalline solids. Crystalline solids are made up of atoms arranged in a definite
pattern. When these solids are heated, the change to a liquid, known as melting, is sharp and
clear. Amorphous substances include rubber, glass, and sulphur. In these substances, the pattern of
atoms is not orderly, and when heated, they gradually soften.

4





     Liquids, on the other hand, are not rigid. If water, milk, or oil is poured on a table, it
will flow all over the surface. The atoms or molecules of liquids attract each other and thereby
enable liquids to flow. But these atoms are loosely structured and do not keep their shape.
Therefore a liquid will take the shape of any container in which it is poured. However, liquids
have a definite volume: a quart of milk cannot fit in a pint container.

5




     Gases, such as air, oxygen, and carbon dioxide, have no fixed shape or volume of their own.
They diffuse or spread out to fill any container. The atoms or molecules of gases are widely spaced
and move very rapidly. They either compress or expand to adapt to any area.

6

     Everything we know is made of matter in solid, liquid or gaseous form.




Organizační diagram