What is Density? Density of various Substances

len Alfred Ajibola - Tue, 10th September, 2019 @ 16:25: PM

Topics in Physics

Derived Units: Similarities and Differences with Fundamental Units Gravity: Interesting facts on Gravity Relative Density of Substances and Specific Gravity Types of Heat Transfer: Conduction Types of Heat Transfer: Convection Types of Heat Transfer: Radiation Physics Scheme of Work, SS1, First Term Physics Scheme of Work, SS1, Second Term Physics Scheme of Work, SS1, Third Term Velocity and Acceleration Newton's Laws of Motion Importance of Gravity What is Density? Density of various Substances Concepts of Force and Motion Motion and Speed Concept of Heat Transfer Concepts of Heat and Temperature Gravity: What is Gravity? Zeroth Law of Thermodynamics - Thermal Equilibrium Fundamental Quantities and Units in Physics

Academic Questions in Physics

Please check out our Test Your Knowledge page to see all Questions and Answers

The rate of change of momentum is proportional to the applied force and will take place in the direction of that force.

The above statement is attributed to _____.

  • A. Albert Einstein

  • B. Isaac Newton

  • C. Galileo Galilei

  • D. Neils Bohr

  • E. Ernest Rutherford

  • F. Marie Curie

The Law of Inertia is also referred to as _____.

  • A. 1st Law of Thermodynamics
  • B. 2nd Law of Thermodynamics
  • C. 3rd Law of Thermodynamics
  • D. Newton's 1st Law of Motion
  • E. Newton's 2nd Law of Motion
  • F. Newton's 3rd Law of Motion

The process whereby the velocity of an object increases and decreases over a period of time is best associated with the term _____.

  • A. Speed
  • B. Velocity
  • C. Momentum
  • D. Constant Velocity
  • E. Acceleration
  • F. Average Velocity

The rate of motion is best referred to as _____.

  • A. Speed
  • B. Velocity
  • C. Momentum
  • D. Inertia
  • E. Acceleration
  • F. Constant Velocity

Consider this expression below:

A body X exerts a force FX on another body Y. In return, body Y exert a force FY back on body X. The forces FX and FY are equal in magnitude but opposite in direction.

Putting the above expression into equation:

FX = -FY

Where FX is the action force

FY is the reaction Force

The above expression relates to _____.

  • A. Theory of Force
  • B. Force Postulate
  • C. Einstein's proposal on Relativity
  • D. Newton's 1st law of motion
  • E. Newton's 2nd law of motion
  • F. Newton's 3rd law of motion

The tendency of a body to remain in a state of rest or in uniform motion is referred to as _____.

  • A. Tension
  • B. Uniform acceleration
  • C. Constant acceleration
  • D. Deceleration
  • E. Inertia
  • F. Velocity

A change in the position of an object with reference to time is best described as _____.

  • A. Momentum
  • B. Displacement
  • C. Velocity
  • D. Acceleration
  • E. Direction
  • F. Motion

The saying 'what goes up on earth must come down' can be best attributed to _____.

  • A. Force
  • B. Motion
  • C. Mass
  • D. Acceleration
  • E. Average velocity
  • F. Constant velocity



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What is Density?

Density relates to the mass and weight of substances. This is so because equal volumes of different substance have got different masses and weights.

For instance; a box containing iron will be heavier (have a higher density) when compared to a similar box containing wood. This is true because wood has a lower density.

Similarly, a glass of water will have a higher density than an exact glass of oil. (Water has a higher density in this case). For this reason, oil floats on water.

Please read on Separation of Mixtures (Water and Oil) here.

Note: The difference in the density of various substances is simply a result of the different atoms that make them up. For instance; water (H2O), which is made up of Hydrogen and Oxygen atoms in the ratio of 2:1 is different from the constituent atoms making up common salt or Sodiun Chloride (NaCl). The constituent atoms in NaCl are Sodiun and Chlorine respectively.

Please read on Periodic Table and Classification of Elements here.

Density is defined as the mass of a unit volume of a material or substance.

Please read more on Matter, Mass and Weight. (The Differences between Mass and Weight is further explained here).

Note: The principle of density was determined by a Greek scientist named Archimedes.

The formula for density is shown below:

ρ = M/V


ρ = density

M= Mass

V = Volume

Please read on Relative Density and Specific Gravity of various Substances here.

Note: "rho" is a Greek letter that expresses ρ (density)

The Standard International (SI) unit for Density is Kilogram per Cubic Metre (Kg/m3).

Please read on the Fundamental and Derived Units here.

The table below shows various substances with their densities:


 DENSITY (Kg/m3)



 Air (1atm and 20oC)


 Bamboo Wood




 Methylated Spirit




 Paraffin Wax




 Water (Fresh Water)


 Sea Water (Saline/Salt Water)


 Blood. Please read on the Red Blood Cells here




 Aluminium  (Al)


 Zinc (Zn)


 Iron (Fe)


 Copper (Cu)


 Lead (Pb)


 Mercury (Hg)


 Gold (Au). Please read Interesting Facts on Gold


 Platinum (Pt)


Notice from the table that helium has a lower density than air and that's one reason why it's used in filling balloons.

Having an understanding of density offers a convenient means of deriving the mass of a body from its volume. Similarly, when we know the mass of a body, we can derive it's density.

Below are the derivation steps:

Mass = Volume x Density (M = Vρ)

Volume = Mass divided by the Density (V = M/ρ)

Note: To get the weight of a body, we will need to multiply its mass by the acceleration of gravity.

Please read more on Gravity here.

A common application of density is seen in the way at which different materials interact with each other.

For instance; a wood may float on water while an iron may sink in it.

Also, balloons will float in air because it's filled with helium gas which is much lighter (has a lower density) than air. Conversely, a nylon filled with sand will not float in air.

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Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.

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Amazing facts in Physics

Glass Ball - Len Academy

Glass Balls actually bounce higher than Rubber Balls

Every planet has its own unique gravitational force. For instance, Mars has a gravity of 3.711 m/s2 while earth’s gravitational force is 9.807m/s2.

Please read on gravity here

When two metals are put together in space, they will stick together as if they are welded. This phenomenon is called cold welding

The fastest animal on land is Cheetah. It can reach a maximum speed of about 113km per hour.

Please read on motion, speed, velocity and acceeration here


The Classical Mechanics (Laws of Motion) is a fundamental part of Physics.

Below are the Newton's Laws of Motion:

An object at rest will continue in its state of rest; while an object in uniform motion will continue in a straight line, unless an external force acts on it.

Newton's First Law of Motion.

Please read on Motion and Speed here.

The rate of change of momemtum is proportional to the applied force and will take place in the direction of that force.

Newton's Second Law of Motion.

To every action, there is an equal and opposite reaction.

Newton's Third Law of Motion.

Please read on Newton's Laws of Motion here.

The study of Thermodynamics revolves around the relationship between heat, temperature, energy and mechanical work; and these can be summarised under the 4 laws of Thermodynamics (Numbered zero through three).

You can read on the Concepts of Heat and Temperature here.

Below are the 4 laws of thermodynamics:

Zeroth law of thermodynamics – If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

Please read on the Zeroth Law of Thermodynamics here.

1st law of thermodynamics – Energy can neither be created nor destroyed but can be changed from one form to another.

You can read on the Food Chain here.

2nd law of thermodynamics – The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

3rd law of thermodynamics – As temperature approaches absolute zero, the entropy of a system approaches a constant minimum.

Fuses are present in many electrical devices. They are basically 🔥 fire-breakers 🔥

If there is a power surge, the fuse will break, preventing damage to the electrical devices. It will also prevent the incidence of 🔥 fire🔥 on or from such device.

Physics is one of the core sciences.

Physics is defined the scientific study of matter and the movement of matter through the space and time of the universe.

Understanding the basic and fundamental concepts of physics will help you better comprehend this subject. Below are some of the concepts:

  1. The Laws of Motion (Classical Mechanics)
  2. Electromagnetism
  3. Relativity
  4. Thermodynamics

Please read on the basic introduction of the above physics concept here