Inter - Molecular Space
2 Minutes
Intermolecular space and matter for kids: explore mass, volume, gaps between molecules, and compressibility. A science lesson in English.
- How plastic and iron balls explain the meaning of mass
- Why sugar fills gaps between water molecules without raising level
- Using a closed syringe to show that air can be compressed
What this lesson teaches
Intermolecular space is the gap found between the individual molecules of any substance. These spaces determine the amount of volume matter occupies and explain how different materials behave when they are mixed, packed, or squeezed together.
Mass and volume of matter
Matter exists as a solid, liquid, or gas, and every form of matter has two fundamental properties called mass and volume. Mass is the total amount of matter an object contains. For example, an iron ball has more mass than an equally sized plastic ball because the iron ball contains more matter inside it. Volume is the actual amount of space that matter occupies.
How molecular gaps affect size
- One kilogram of iron and one kilogram of cotton have the exact same mass because both contain the same amount of matter.
- The molecules in iron are packed tightly together with very little space between them, so the iron stays compact and occupies a small volume.
- The molecules in cotton have larger gaps between them, which causes the cotton to spread out and occupy far more space.
- Even when two objects have the same mass, differences in the gaps between their molecules result in different volumes.
Why sugar does not raise the water level
Water contains empty spaces between its molecules. When sugar is added to water, the sugar molecules move into and settle inside these existing gaps. Because the sugar molecules fill the open spaces instead of taking up separate room, the overall water level does not increase. In contrast, an object like a stone cannot fit into the gaps between water molecules, so it sinks to the bottom, pushes the water out, and forces the water level to rise.
Compressibility of air
In certain states of matter, the gaps between molecules can be squeezed together to make the total volume smaller. When the space between molecules can be reduced by force, that substance is said to have compressibility. Air has this property because there is room between its molecules to be squeezed. If air is trapped inside a syringe with the opening blocked, pushing the plunger compresses the air to a certain extent.