Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Matter is anything that has mass and occupies space. All matter is made up of tiny particles called molecules.
Molecules are held together by a force called the 'Intermolecular force of attraction'.
The empty space between the molecules is known as 'Intermolecular space'.
In Solids, molecules are very closely packed. They have a very strong intermolecular force and negligible intermolecular space, resulting in a fixed shape and volume.
In Liquids, molecules are less closely packed compared to solids. They have moderate intermolecular space and weaker forces, allowing them to flow and take the shape of the container while maintaining a fixed volume.
In Gases, molecules are far apart with very large intermolecular spaces and very weak intermolecular forces. They have no fixed shape or volume and occupy all available space.
State changes occur when heat is added or removed. For example, water exists as ice (solid), water (liquid), and steam (gas), all represented by the formula .
📐Formulae
💡Examples
Problem 1:
Why does a gas fill the entire space of a closed bottle while a solid piece of stone stays in one corner?
Solution:
Gases have very weak intermolecular forces and large intermolecular spaces.
Explanation:
In a gas, the molecules move randomly in all directions because the force of attraction between them is negligible. In contrast, molecules in a solid stone are held tightly by strong intermolecular forces, preventing them from moving away from their fixed positions.
Problem 2:
What happens to the molecular arrangement of when it is cooled from to ?
Solution:
The molecules slow down and move closer together to form a rigid structure.
Explanation:
Cooling removes thermal energy. As water () cools to , the kinetic energy of the molecules decreases, the intermolecular forces become stronger, and the molecules arrange themselves into a fixed pattern, turning the liquid into ice (solid).
Problem 3:
Arrange the states of matter in increasing order of 'Intermolecular Space'.
Solution:
Explanation:
Solids have the least space between molecules because they are tightly packed. Liquids have more space than solids, and gases have the maximum amount of space between their molecules.