Page 43 - Summary 6 2025

Delta Modern Language Schools
Science department
Grade 6
1st term 2024- 2025

You have learned that matter behave differently when they are heated or cooled,
where:
- When we cool a matter, the spaces between its molecules decrease and the molecules

come close together (contract) and this is called "contraction".

- When we heat a matter, the spaces between its molecules increase and the molecules

spread out (expand) and this is called "expansion".

Examples of the contraction and expansion of some matter.
►Thermometer:
- Some thermometers contain alcohol (liquid) mixed
with color.

► When the thermometer is placed in hot substance, the
temperature of alcohol increases and the spaces between its
molecules increase, so the molecules of alcohol spread out and
expand giving high level of temperature in the thermometer.

► When the thermometer is placed in cold substance, the
temperature of alcohol decreases and the spaces between its
molecules decrease, so the molecules of alcohol come close
together and contract giving low level temperature in the thermometer.

►Jars :

- Sometimes it is hard to open the lid of the jar.
- When you pour hot water on the lid of the jar, it opens easily, where:
• The lid of the jar is made of metal.
• When hot water is poured on the metal lid, the temperature of the
metal lid increases and the spaces between its molecules increase, so
the molecules of metal lid spread out and expand, so it can be easily
opened.

40