Page 130 - Active Science 5 Ebook and Activity

• Molecules in solids are very tightly packed.
Let’s Pronounce Together
• Molecules in liquids have free space between them.
molecule sequence
• Molecules in gases cause them to spread easily.
negligible intermolecular
• A physical change is temporary and reversible whereas reversible
chemical change is permanent and irreversible.

Glossary

• Matter : Anything that has mass and occupies space.
• Atom : Smallest unit of matter.
• Molecule : Atoms combine to form molecules.
• Density : Property of matter which tells about how tightly packed the matter
is.
• Physical Change : Change in the physical state of matter.
• Chemical Change : Change in the chemical properties of a substance.

Practice Time

A. Choose the correct option.
1. Matter is made up of tiny units called _____________.

a. atoms b. elements
c. molecules d. particles

2. Molecules in a liquid are ______________.
a. very loosely packed

b. very tightly packed
c. not packed

d. loosely packed
3. Gases ______________.
a. cannot flow

b. flow in all directions
c. can flow in two directions

d. can flow in one direction
4. The force of attraction amongst molecules of solids ______________.

a. is the least b. less
c. great d. does not exist
5. A symbol is used for ______________.

a. an element b. an atom
c. molecules d. substances

130 Active Science-5