Physics

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

An 🍎 apple 🍎 falling from a tree has an unbalanced force.

  • A. True

  • B. False

Force is a quantity measured in _____.

  • A. Kilogram

  • B. Gravity

  • C. Incandescence

  • D. Meter per second square (ms-1)

  • E. Mole

  • F. Newton

Heat transfer indicates two systems of varying temperatures and will always be transferred from a region with lower temperature to another with higher temperature.

  • A. True

  • B. False

Heat can be created.

  • A. True

  • B. False

Temperature is defined as the measure or ability of an object or substance to transfer heat energy to another object or substance.

  • A. True

  • B. False

Which of the following statement is incorrect concerning gravity?

  • A. It is a natural force of attraction

  • B. The earth is spherical in shape and we don't fall off it due to gravity

  • C. The amount of gravity is the same all around the spherical earth

  • D. Earth's gravity affects the satellites

  • E. Gravity is affected by size and closeness of objects

  • F. In an ideal space environment, gravity is absent

If two bodies are in thermal equilibrium with another body, then they are also in equilibrium with each other.

The above statement is the _____ law of thermodynamics.

  • A. Zeroth

  • B. First

  • C. Second

  • D. Third

  • E. Fourth

  • F. Fifth

Which of the following is a derived unit?

  • A. Kelvin

  • B. Meter

  • C. Newton

  • D. Candela

  • E. Mole

  • F. Ampere

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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

Where:

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:

 SUBSTANCE

 DENSITY (Kg/m3)

 Helium

 0.179

 Air (1atm and 20oC)

 1.20

 Bamboo Wood

 400

 Ethanol

 810

 Methylated Spirit

 800

 Benzene

 900

 Paraffin Wax

 900

 Ice

 920

 Water (Fresh Water)

 1000

 Sea Water (Saline/Salt Water)

 1030

 Blood. Please read on the Red Blood Cells here

 1600

 Glass

 2600

 Aluminium  (Al)

 2700

 Zinc (Zn)

 7100

 Iron (Fe)

 7900

 Copper (Cu)

 8900

 Lead (Pb)

 11300

 Mercury (Hg)

 13600

 Gold (Au). Please read Interesting Facts on Gold

 19300

 Platinum (Pt)

 21500

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

One quarter of an 🍎 apple 🍎 is filled with air and that's why they float in 💦 water 💦

The Nobel price was named after its founder, Alfred Noble. He is a Swedish, born on October 21, 1833; and was the inventor of dynamite. He was also a a famous scientist and a successful business man.

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


NOTABLE POINTS IN Physics

The earth is governed by the force of gravity and that’s why everything present on it (humans, plants, animals and even air) is always drawn towards it. You will actually need some form of force greater than gravity in order to pull yourself away from the earth.

As an instance, the earth as we know is spherical in shape and held in space. Also, all humans live on a constantly rotating earth and not inside the earth. Since we live on a spherical earth held in space, how come humans are yet to fall off the constantly rotating earth?

Well, the answer is gravity. Even if we attempt to jump off the earth into space, the force of gravity present on earth will still pull us down. In fact, in order to leave the earth; there has to be a force stronger that gravity; which must be applied to whatever is attempting to leave the earth. For this reason:

Whenever one jumps, a certain amount of force is needed to be applied by that person. However, gravity still return the person back to earth because the applied force had been exhausted.

Please read more on the concept of gravity here.

The larger the size of an object, the greater it’s force of gravity. Gravity is therefore affected by the size and closeness of objects.

Since the earth is larger than the moon, it will have a greater gravitational force than the moon. We will be more attracted on the earth than we would on the moon if we were astronauts on the moon. This implies that we will weigh differently on both places. For this reason, our weight will also vary on the various planets (because they are of different sizes). This is shown in the diagram below:

Weights on planets - Len Academy

Weight depends on the degree at which the gravity on earth or moon or another planet pulls an object while the Mass of any object or body will always remain the same (constant) since it’s the amount or quantity of matter in the body.

Please read on Mass versus Weight here

Zeroth Law - Len Academy

To better understand what the Zeroth Law of Thermodynamics meant, we need to know what thermal equilibrium is. This is explained below:

Two bodies A and B are said to be in thermal equilibrium if each body can transfer heat to each other when placed closed together but ended up not transferring any heat to each other.

This will mean that both bodies are at equal temperature.

Now, according to the zeroth law, assuming we have three bodies namely X, Y and Z:

If X = Y and Z = Y, then X = Z

From the above expression, it will be observed that: if X and Y are in thermal equilibrium and Z and Y are in thermal equilibrium, therefore, X and Z must be in thermal equilibrium too.

So we can see that according to the zeroth law, temperature is a quantity worth measuring.

It can therefore be said that temperature is the quantity that remains constant (the same) for all systems in thermal equilibrium.

Consequently, the Zeroth Law of Thermodynamics states that if two separate bodies are in thermal equilibrium with another body, then they are also in equilibrium with each other

Please read more on the Zeroth Law of Thermodynamics here

Fundamental units are the units of fundamental quantities.

A fundamental unit is a unit that does not depend on any other unit; neither can it be changed nor is related to another fundamental unit.

Note: A fundamental unit is also referred to as a basic unit.

Fundamental Units are always constant. This means that they don't change, (remains the same) and are standardized all over the world.

The fundamental quantities alongside their respective fundamental unit are 7 in number. They include:

  1. Mass (m) is a fundamental quantity whose unit is kilogram (kg)

  2. Length (l) is a fundamental quantity whose unit is meter, (m)

  3. Time (t) is a fundamental quantity whose unit is second (s)

  4. Temperature (T) is a fundamental quantity whose unit is Kelvin (k)
    You can read on the Concept of Temperature and Heat here.

  5. Electric Current (I) is a fundamental quantity whose unit is ampere (A)

  6. Amount of Substance (n) is a fundamental quantity whose unit is mole (mol)

  7. Luminous Intensity (|v) is a fundamental quantity whose unit is candela (cd)

Please read more on fundamental units 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.