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.
Solids: Molecules are very closely packed with strong forces of attraction. They have a definite shape and a definite volume (e.g., a wooden block or a crystal).
Liquids: Molecules are less closely packed than solids. They have a definite volume but no definite shape; they take the shape of the container they are poured into (e.g., or oil).
Gases: Molecules are very far apart with very weak forces of attraction. They have neither a definite shape nor a definite volume and fill the entire space available to them (e.g., or ).
Change of State: Matter can change from one state to another by heating or cooling. For example, heating ice () turns it into water ().
Solute, Solvent, and Solution: A solute (like sugar) dissolves in a solvent (like ) to form a solution.
📐Formulae
💡Examples
Problem 1:
What happens to the molecules of water () when it is heated to form steam?
Solution:
The molecules move further apart and start moving faster.
Explanation:
Heating provides energy to the molecules, allowing them to overcome their forces of attraction and transition from the liquid state to the gaseous state (steam).
Problem 2:
If you dissolve of salt in of water, identify the solute and the solvent.
Solution:
Solute: Salt; Solvent: Water ().
Explanation:
The substance that is dissolved is the solute, and the medium in which it is dissolved is the solvent.
Problem 3:
Why can a gas be compressed easily while a solid cannot?
Solution:
Because of the large intermolecular spaces in gases.
Explanation:
In gases, molecules are far apart. Applying pressure pushes them closer together. In solids, molecules are already tightly packed with no space to move closer.