Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Matter is anything that has mass () and occupies space (Volume, ).
Materials can be classified based on their state: Solids (fixed shape), Liquids (flow and take shape of container), and Gases (no fixed shape or volume like ).
Hardness: Some materials are hard (like diamond or iron) and cannot be easily scratched, while others are soft (like rubber or sponge).
Solubility: Materials that dissolve in water () are called soluble (e.g., salt, sugar), and those that do not are called insoluble (e.g., sand).
Transparency: Materials are classified as Transparent (clear glass), Translucent (frosted glass), or Opaque (wood, metals) based on how much light passes through them.
Flexibility: Materials like rubber are flexible and can bend, whereas materials like glass are brittle and break easily.
Lustre: Metals like gold () and silver () have a shiny appearance called metallic lustre.
📐Formulae
💡Examples
Problem 1:
Identify which of the following is an opaque material: A clear glass window, a piece of wood, or a thin muslin cloth?
Solution:
A piece of wood.
Explanation:
A piece of wood is opaque because it does not allow any light to pass through it, unlike clear glass which is transparent.
Problem 2:
Why does sugar disappear when stirred in a glass of water ()?
Solution:
Because sugar is soluble in water.
Explanation:
Sugar particles occupy the empty spaces between the molecules of water (), forming a uniform solution.
Problem 3:
Calculate the total mass if we mix of salt and of water.
Solution:
Total Mass = .
Explanation:
According to the law of conservation of mass, the total mass of the mixture is the sum of the individual masses: .