[1NA] Chapter 2: Exploring Diversity of Matter by Their Physical Properties

Common Physical Properties (IMPORTANT)

  1. Ductility : property of a material to stretch without getting damaged. It is getting pulled!
    • example: a piece of gold is drawn into a long piece of wire.
  2. Malleability : property of a material to deform under compression. It is getting pushed!
    • example: a dent in a material is possible because it is malleable.
  3. Flexibility : property of a material to bend without breaking and return to its original size and shape after bending.
    • example : a fishing rod allows for bending and returning to its original shape once no fish is pulling on the hook.
  4. Melting point : temperature at which a material changes from solid state to liquid state.
    • example: wax melts easily because it has low melting point. Ice melts even more easily because its melting point is even lower than that of wax.
  5. Boiling point: temperature at which a material changes from liquid state to gaseous state.
    • example: alcohol evaporates quickly because it has a low boiling point.
  6. Hardness: property of a material to withstand scratches.
    • example: a diamond is used to cut mirror because diamond is harder than mirror.
  7. Strength: property of a material to support load without breaking or tearing.
    • example: spider web is very strong and that’s why it can support very heavy weight without breaking. Our hair is also quite strong.
  8. Thermal conductivity: a measure of how fast heat can flow through a material.
    • example: if we hold a metal rod in one hand and a wooden rod in the other hand. We will get our hand scalded (one that is holding the metal rod but not the wooden ones) if we try to put the ends of both rods on fire.
  9. Electrical conductivity: a measure of how fast/readily electricity can flow through a material.
    • example: copper is used to make our electrical wire that we use every day. Most metals are good conductor of electricity and that’s why we must never try to stick a metal into the power socket with our bare hand. Life is precious!
  10. Density : quantity of matter packed into a unit volume of the material.
    • example: beautiful iceberg! so big and so heavy and yet it seems to float effortlessly.

Questions Worth Pondering

  1. Why do we need S.I units?
  2. Why do we need to know the physical properties of materials?

Points To Note

  1. There are 7 base quantities: mass (kg), length (m), time (s), temperature (k), current (A), amount of substance (mol), luminous intensity (cd). At this level, we focus on those base physical quantities that are in bold.
  2. Deducing if a body will float or sink, we need to compare their densities. Object will lower density, will float/remain above object with higher density. If a solid object has the same density as the fluid, then when place inside the fluid, the object will neither sink nor float.
  3. To avoid making parallax error, all measurements must be taken at eye level and directly perpendicular to the scale/reading.
  4. A pure substance will always have the same fixed melting point and boiling point.
  5. Density of an object does not change by physical mean. Example, if you tear a piece of paper into two halves, the density of each half still remain the same as the density of the original piece.

Choice of terms

  • strength – strong/weak
  • hardness – hard/less hard/ soft
  • density – denser/less dense (Reject – lighter and heavier)
  • Flexibility – flexible/rigid
  • Electrical conductivity – good conductor/poor conductor of electricity.
  • Thermal conductivity – good conductor/poor conductor of heat. Reject – insulator unless it is used to refer to vacuum.
  • Melting/boiling point – high/low
  • Time – shorter/longer time taken