Mass, Volume, Density and Buoyancy
Ex Video mass, volume and Density 6:48 min https://www.youtube.com/watch?v=JWIhtSWhUrY
Video Buoyancy, floating or sinking 2;17 min https://www.youtube.com/watch?v=06TFRgPlmxU
Mass
• Mass is the amount of matter in an object.
• Measured in kilograms (kg) or grams (g).
• Mass does not change with location (e.g., Earth vs Moon).
Volume
• Volume is the amount of space an object takes up.
• Measured in cm³, mL, or L.
• For regular shapes (e.g., a cube), you can calculate volume using formulas. • For irregular
objects, volume can be measured using water displacement.
Density
• Density tells us how much mass is packed into a certain volume.
�� = density
��= mass
��= volume
• Units: g/cm³ or kg/m³.
• Low density = particles more spread
out.
• High density = particles packed tightly
Example 1:
A block has a mass of 200 g and a volume of 50 cm³.
• Density = Mass ÷ Volume
• Density = 200 g ÷ 50 cm³
• Density = 4 g/cm³
Example 2:
Why Objects Float or Sink
Density and Floating
• If an object’s density is less than water (1 g/cm³) → it floats.
• If an object’s density is greater than water → it sinks.
Buoyant Force (Upthrust)
• Fluids push upward on objects — this is buoyancy.
• The buoyant force = weight of the fluid displaced (Archimedes’ Principle).
• If buoyant force ≥ object’s weight, it floats.
• If weight > buoyant force, it sinks.
Why Shape Matters
• A steel nail sinks because it has a high density and cannot displace enough water.
• A large steel ship floats because it has a hollow shape filled with air, giving it a low average density
that is less than water.
• Bigger volume = more water displaced = greater buoyant force.
Quiz 1 – 10 MCQs
https://www.proprofs.com/quiz-school/story.php?title=mass-volume-density-1 Quiz 2
Isaacscience 12 MCQs https://isaacscience.org/questions/density_quiz_a
Density Table
• The table below shows the density of some solids, liquids, and gases.
Substance
State
Density (kg/m³)
Density (g/cm³)
Iron
Solid
7,870
7.87
Aluminium
Solid
2,700
2.70
Solid
8,960
Solid
19,300
Solid
700–900
Solid
917
Liquid
1,000
Mercury
Liquid
789
13.6
Olive Oil
Liquid
13,600
0.92
Glycerin
Liquid
920
1.26
Air
Liquid
1,260
0.001225
Oxygen (O₂)
Gas
1.225
0.001429
Gas
1.429
Gas
1.251
Gas
1,977
Copper
Gold
Wood (Oak)
Ice
Water (20°C)
Ethanol
Nitrogen (N₂)
Carbon Dioxide (CO₂)
Hydrogen (H₂)
8.96
19.3
0.7–0.9
0.917
1.00
0.789
0.001251
0.001977
0.0000899
Gas
0.0899
0
