Thermal Properties of Matter refer to the characteristics and behaviors of substances related to heat and temperature. These properties play a crucial role in understanding how materials respond to changes in temperature and how they conduct store, or transfer heat. Some of the key thermal properties of matter include temperature, heat capacity, specific heat capacity, thermal conductivity, thermal expansion, phase change, melting, and boiling point, among others.

In this article, we are going to explore how temperature changes affect various properties of matter. We will discuss different thermal properties that are important to study to understand the nature of any material and the effects caused by temperature changes on it.

What are the Thermal Properties of Matter?

Thermal properties refer to the characteristics and behavior of materials in response to changes in temperature. These properties tell us how a substance behaves when its temperature changes. These properties are essential in understanding how a material interacts with thermal energy and how it conducts, stores, or dissipates heat.

Thermal Properties Definition

Thermal properties refer to the characteristics or attributes of a material or substance that describe how it responds to changes in temperature and heat.

Examples of Thermal Properties

There are many thermal properties associated with matter, A few of the important properties are as follows:

• Temperature
• Heat Capacity
• Specific Heat Capacity
• Thermal Conductivity
• Thermal Expansion
• Phase Change
• Melting Point
• Boiling Point

Heat and Temperature

Let’s talk about heat and temperature ! Heat is like warmth, and temperature tells us if something is hot or cold. Lets see one by one about heat and temperature.

Heat Definition

Heat is a form of energy which can be transferred between two or more systems or between system and its surrounding by the change of temperature.

Heat tends to move from higher temperature region to lower temperature region. Unit of heat is Joule in SI system and calorie in CGS system.

Temperature Definition

Temperature is the degree of hotness of body.

When body is heated its temperature increases and when body is cooled its temperature decreases. Unit of temperature in SI system as well as CGS system is Kelvin.

Measure of Temperature

The temperature of body is measured by using an instrument called thermometer.

Following are some scales which are used to measure the temperature

• Kelvin Scale: The lower fixed point is 273.15 K and upper fixed point is 373.15 K.
• Celsius Scale: The lower fixed point is 0 ℃ and upper fixed point is 100 ℃.
• Fahrenheit Scale: The lower fixed point is 32 ℉ and upper fixed point is 212 ℉.
• Reaumur Scale: The lower fixed point is 0 °R and upper fixed point is 80 °R.

Relation between above scales is given by,

(℃ / 5) = ( F – 32 ) / 9 = R / 4 = ( K – 273 )/5

Absolute Temperature

The kelvin scale of temperature measurement is considered as absolute temperature scale. The temperature 0 K is called as absolute zero which corresponds to -273.15 ℃.

Read More about Difference Between Heat and Temperature.

Heat Capacity

The amount of heat required to raise the temperature of a given amount of substance by 1℃ is called as heat capacity per

Note: Heat Capacity is an extensive property which depends on mass of substance.

Heat Capacity Formula

Heat Capacity Formula is given as:

Q = m × c × ΔT

Where,

• Q = heat capacity
• m = mass of substance
• c = specific heat capacity of substance
• ΔT = change in temperature

Read More about Heat Capacity.

Specific Heat Capacity

The amount of heat required to raise the temperature of unit mass of body by 1 ℃ is called as specific heat capacity of substance.

It is denoted by ‘c’ and formula to calculate specific heat capacity is given as,

c = ΔQ / (m × ΔT)

Where,

• ΔQ is amount of heat given to the substance
• m is mass of substance
• ΔT is Temperature change

Read more about Specific Heat Capacity.

Molar Specific Heat

Specific heat of unit mole of substance is called molar specific heat of substance. The amount of heat required to raise the temperature of 1 mole of substances by 1 ℃ is called molar specific heat.

There are two types of molar-specific heat

Molar Specific Heat at Constant Volume: The amount of heat required to raise the temperature of 1 mole of substance by 1 ℃ by keeping volume constant.

Molar Specific Heat at Constant Pressure: The amount of heat required to raise the temperature of 1 mole of substance by 1 ℃ by keeping pressure constant.

Thermal Expansion

Thermal Expansion is tendency of substance to change its shape , size or volume in response to a change in temperature.

Thermal expansion is minimum in case of solids and maximum in case of gases because intermolecular forces are maximum in solids and minimum in gases.

Thermal Expansion In Solid

Solids can expand in one dimension (linear expansion) , two dimension (superficial or areal expansion) and three dimension (cubical or volume expansion).

Linear Expansion

When a solid is heated and its length increases, then the expansion is called linear expansion. Change in length is given as

ΔL = L_°αΔT

Where,

• ΔL is change in length
• L_° is original length
• α is coefficient of linear expansion
• ΔT is temperature change

Coefficient of Linear Expansion: The increase in length per unit original length of rod per unit ℃ or K rise in temperature.

Superficial (areal) Expansion: When the temperature of two dimensional solid material changes , its area also changes and this is called superficial expansion.

Change in area is given as

ΔA = A₀βΔT

Where

• ΔA = change in area
• A₀ = original area
• β = coefficient of superficial expansion
• ΔT = temperature change

Coefficient of Superficial (areal) Expansion: The change in area per unit original surface area of body per unit rise in temperature.

Cubical (volume ) Expansion : When the temperature of solid increases , it volume increases , this expansion is called volume expansion.

Change in volume is given as

ΔV=V₀γΔT

Where

• ΔV = change in volume
• V₀ = original volume
• γ = coefficient of volume expansion
• ΔT = temperature change

Coefficient of superficial expansion: The change in volume of body per unit original volume of body per unit rise in temperature.

Thermal Expansion in Liquid

Liquids acquire the shape of container in which they are present , so we cant study areal and linear expansion of liquids . The observed expansion of liquid is not real , it is apparent expansion.

Coefficient of Apparent Expansion of Liquid (γ_a): It is defined as the apparent increase in the volume of liquid per unit original volume for unit rise in temperature.

Coefficient of Real Expansion of Liquid (γ_r): It is defined as the real increase in the volume of liquid per unit original volume for unit rise in temperature.

γ_a = ( apparent increase in volume) /(original volume × change in temperature )

γ_a = ΔV_a/VΔT

Thermal Expansion of Gases

In gases the expansion is very much as compared to solids and liquids. The expansion of container is negligible in case of gases , so it is only real expansion. Gases have no definite shape so they have only volume expansion.

Read More about Thermal Expansion .

Thermal Conductivity

Thermal conductivity is the property of material that describes the ability of material to conduct heat.

Coefficient of thermal conductivity is defined as the quantity of heat that flows in steady state per unit time through the material of unit cross sectional area when the temperature gradient is maintained.

Conductivity in Different Materials

Conductivity of Different Materials are listed in the following table:

Note: Generally metals have higher thermal conductivity than non-metals.

Latent Heat

The amount of heat absorbed or released by unit mass of substance during change of state of substance without changing nits temperature is called latent heat.

Latent Heat Formula

Latent Heat Formula is given as

L = Q / m

where

• m is mass of substance
• Q is amount of Heat Absorbed

Latent Heat in Phase Transitions

Latent Heat of Fusion: The amount of heat absorbed by unit mass of substance during its conversion from solid state to liquid state at its melting point is called latent heat of fusion.

Latent Heat of Vaporisation: The amount of heat absorbed by unit mass of substance during its conversion from liquid state to gaseous state at its boiling point is called latent heat of vaporisation.

• Latent heat of fusion of ice is 80 cal / g.
• Latent heat of vaporisation of water is 540 cal/ g.

Read More,

• Latent Heat
• Latent Heat of Fusion 

Modes of Heat Transfer

The transfer of heat energy takes place by one of the following modes :

• Conduction
• Convection
• Radiation

Let’s dicuss these modes of heat transfer as follows:

Conduction

The phenomenon of transfer of heat energy from one part of solid to another part at lower temperature without any movement of molecules in material . It occurs in solid where heat is transferred from one particle to another through direct contact.

Read More about Conduction.

Convection

The transfer of heat energy through material medium due to actual motion of the particles of the medium is called convection.

Read More about Convection.

Radiation

The transfer of heat through electromagnetic waves that do not require a medium for propogation is called radiation.

Heat transfer can be calculated using the formula

Q = m × c × ΔT

where,

• Q = heat transfer
• m = mass of substance
• c = specific heat capacity of substance
• ΔT = change in temperature

Read More about Heat Transfer Formulas.

Melting , Boiling and Freezing Points

Let’s understand these concepts by differentiating them.

Also, Check

• Thermodynamics
• Thermodynamic Processes
• Thermodynamic Cycles

JEE Questions: Thermal Properties of Matter

Q1: A 150 g block of copper at 125°C is placed in a 250 g of water at 25°C. Assuming no heat loss to the surroundings, what is the final equilibrium temperature of the mixture? The specific heat capacity of copper is 0.385 J/g°C and of water is 4.18 J/g°C

Q2: A steel rail (coefficient of linear expansion = 12 × 10^-6/°C is 10 m long at 20°C. If the temperature rises to 40°C, what is its new length?

Q3: A sealed balloon contains 2.00 moles of helium gas at 300 K. If the temperature is increased to 600 K, and the volume remains constant, what is the final pressure of the gas, given the initial pressure was 1 atm?

Q4: A concrete bridge is constructed with a gap between sections to allow for expansion during hot weather. If each section of the bridge is 100 meters long at 15°C, and the coefficient of linear expansion for concrete is 12 × 10^-6/°C how much will a single section expand if the temperature rises to 35°C?

Neet Questions: Thermal Properties of Matter

Question 1: A Centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers 140∘C. What is the fall in temperature as registered by the centigrade thermometer.

a: 80 ℃ b: 60 ℃ c: 40 ℃ d: 30 ℃

Solution:

We have formula for conversion in these given two scales of temperature

℃/5 = (℉-32 ) / 9

given ℉ = 140

℃ = (140 – 32 ) × 5 / 9 = 60

so the centigrade temperature is 60 ℃

Since initially it is kept in boiling water so temperature was 100 ℃

so fall in temperature as registered by centigrade thermometer is 100 – 60 = 40 ℃.

Question 2: Mercury thermometer can be used to measure temperature up to

a: 260 ℃ b: 100 ℃ c: 360 ℃ d: 500 ℃

Maximum limit of measuring temperature using mercury thermometer is 360 ℃.

Question 3: The absolute zero is

a: 0 ℉ b: 0 ℃ c: 273 K d: -273 ℃

Solution:

The absolute zero temperature is -273 ℃.

Thermal Properties of Matter Examples

Example 1: The length of a metal rod at 15 ℃ is 50 cm and at 90 ℃ is is 50.15 cm . The coefficient of linear expansion of the material rod is

Solution:

For linear expansion , we have

ΔL=L_°αΔT

and ΔL = L₂ -L₁

Given L₁ = 50 cm ,L₂ = 50.15 cm , T₁ = 15 ℃ , T₂ = 90 ℃

α = (L₂ -L₁) / L₁ × ( T₂ – T₁ ) = ( 50.15 – 50 ) / 50 × (90 – 15 )

⇒ α = 0.15 / 50 × 75

⇒ α = 4 × 10 ^-5 Per ℃

Therefore the coefficient of linear expansion of material rod is 4 × 10 ^-5 /℃.

Example 2: Iron sheet 50 cm × 20 cm is heated through 100 ℃ . If α = 12 × 10 ^-6 / ℃ , the change in area is

Solution:

For areal expansion , we have

ΔA = AβΔT

Given: α = 12 × 10 ^-6 / ℃

so β = 2 × α = 24 × 10 ^-6 / ℃

given A = 50 cm × 20 cm = 1000 cm² , ΔT = 100 ℃

ΔA = AβΔT = 1000 × 24 × 10 ^-6 × 100 = 2.4 cm²

Therefore the change in area of sheet is 2.4 cm². 

Example 3: The volume coefficient of expansion of a metal whose linear coefficient is 15 × 10 ^-6 / ℃ is

Solution:

γ = 3 × α

⇒ γ = 3 × 15 × 10 ^-6

⇒ γ= 45 × 10 ^-6 / ℃

Example 4: If coefficient of superficial expansion of a solid is 2 × 10 ^-5 / ℃ , its coefficient of linear expansion is

Solution:

β = 2 × α

⇒ α = β / 2 = 2 × 10 ^-5 / 2

⇒ α = 1 × 10 ^-5 / ℃

Practice Problems on Thermal Properties

Problem 1: A metal rod having a coefficient of linear expansion of 2 × 10 ^-5 / ℃ has a length of 100 cm at 20 ℃ . The temperature at which it is shortened by 10 mm is

Problem 2: Temperature at which coefficient of cubical expansion of water is zero is

Problem 3: A bar of iron is 10 cm at 20 ℃ . At 19 ℃ its length will be ?

Thermal Properties of Matter FAQs

Which are Thermal Properties of Matter?

Specific Heat Capacity , Thermal Expansion , Thermal Conductivity , Thermal Stress , Latent Heat are the thermal properties of substance.

What is K in Thermal Properties of Matter?

In thermal properties of matter, “K” represents thermal conductivity, a measure of a material’s ability to conduct heat.

What are the Important Topics in Thermal Properties of Matter?

Important topics in the study of thermal properties of matter include:

• Temperature and Heat
• Specific Heat Capacity
• Thermal Expansion
• Thermal Conductivity
• Laws of Thermodynamics
• Heat Transfer Mechanisms (Conduction, Convection, Radiation)
• Phase Transitions (Melting, Boiling, Freezing)
• Heat Engines and Efficiency
• Calorimetry
• Thermodynamic Processes

What are the Modes of Transfer of Heat ?

The modes of transfer of heat are conduction , convection and radiation.

What is Anomalous Expansion of Water ?

If the temperature of water is in the range 0 ℃ to 4 ℃ , water expands on cooling and contracts on heating . This behaviour of water is called as anomalous expansion of water.

What is Specific Heat Capacity of Substance ?

The amount of heat required to raise the temperature of unit mass of body by 1 ℃ is called as specific heat capacity of substance.

What is the Relationship between Coefficient of linear Expansion and Superficial Expansion of Solid ?

Coefficient of linear expansion (α) and coefficient of superficial expansion (β) are having relationship β = 2 × α.

What is Calorimeter?

The device which is used to measure heat exchange in a chemical or physical process is called calorimeter and it is used to measure specific heat of substance.