Thermodynamics: Kinetic Theory of Matter | Free Essay Example

Thermodynamics: Kinetic Theory of Matter

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Topic: Sciences

How does the study of heat relate to the kinetic theory of matter?

The kinetic theory of matter maintains that matter comprises tiny particles that are separated and in constant motion. These molecules collide with the walls of a container they are placed in. The theory gives an experimental explanation to the physical behavior of matter such as heat transfer. Gases, liquids, and solids keep on changing their state when the heat is added or reduced. Solids have their particles in a regular compact, closely attracted to one another as they keep vibrating in fixed positions.

Liquids contain particles that have a relative distance between them but irregularly arranged. They also have a faster movement while sliding over each other. The liquids contain more energy gained from the heat and have the ability to flow. Gases, on the other hand, contain particles that are distanced and in the random and rapid movement to occupy any unfilled space (Burshstein, 2006). When gas is placed in a container, it bombards the walls to create pressure.

The addition of heat adds more energy to the matter, making it convert from solid to liquid and gas, respectively. Conversely, reducing heat converts matter from gas to liquid and then to solid. Molecular motion is, therefore, dependent upon the rise or reduction of heat to define the physical properties of matter. At absolute zero, molecular motion lacks in the matter. Matter keeps changing its state depending on the amount of heat applied. For instance, to describe how a study of heat relates to the kinetic theory of matter, an experiment on the melting of ice is the best way to demonstrate molecular motion.

Applying more heat on an ice cube makes it change into a liquid through a process referred to as melting. More heat application converts the liquid into a gaseous state in a process called evaporation. From the experiment, it is clear that an ice cube has a definite shape, but this is distorted when the heat is added. From this, the kinetic theory maintains that matter has particles that are in constant motion while adding heat enhances the molecular motion since more energy is added to the particles. Conversely, reducing heat depict energy withdrawal from the particles and therefore, matter change from gas to liquid in a process called condensation. More heat reduction changes the liquid into solid in a process called freezing (Burshstein, 2006).

What is heat?

Heat is termed as the transmission of energy between physical bodies. Heat is also said to be energy transfer between two thermodynamic systems when there is a temperature variance, and thermal exchange is possible. Heat is, therefore, a transfer of thermal energy. It is also referred to as the transfer of spontaneous energy between physical bodies whose temperature varies. Energy transfer from a body with high temperature to another with lower temperature is what is recognized as heat. As a result, heat is transit energy, and when it’s supplied in a body, it is kept as the potential or kinetic energy of the molecules present.

Heat is energy, and its addition is said to be an addition of energy. The addition of heat causes a rise of temperature hence a rise in the average kinetic energy of particles, which makes them move faster. Rise or decline in heat causes matter to modify the state to melt, condense, evaporate, or even freeze. Temperature does not always rise with heat since, at some point, energy added is used to separate bonds that hold the molecules together and change their average kinetic energy as they absorb energy to melt or release energy to freeze. Heat cannot be measured directly, but its physical impact is seen. Heat always flows from warm to cooler objects, which are in contact to achieve a similar temperature and achieve thermal equilibrium (Jha, 2004).

What is the temperature?

Temperature is the kinetic energy present in the particles. Temperature is recognized as a physical property, which defines whether an object is cold or even hot. This is expressed as Celsius, Fahrenheit, or Kelvin scale in a thermometer. Temperature denotes the amount of thermal energy. A large sample contains less temperature as compared to smaller samples with a similar amount of thermal energy introduced. Hence, the temperature is a quantity of kinetic energy of particle i.e., at absolute zero, it is the temperature whereby the particles consist of zero kinetic energy and cannot get any colder but vibrate in one position (Jha, 2004).

What is the relationship between heat and temperature?

Heat and temperature are related by the kinetic theory of matter that defines the changes of the physical state of matter. Heat and temperature are connected by a concept called the latent heat of a substance. This is the energy required to convert the state of matter without changing its temperature. For instance, an ice cube changes state when its temperature rises as a result of the addition of heat. However, at a particular point, the temperature stays constant even as heat is added since the energy added is used in disintegrating the crystalline bonds of a solid to result in a liquid. The energy needed to covert a kg of the sample into solid and vice versa is called the latent heat of fusion (Tillery et al., 2006).

More energy addition results in a rise in temperature up to 100oC, and the temperature stagnates again for the energy supplied by the addition of heat is used to separate the bonds of water molecules to give out a gas. Heat cannot be quantified directly but can be denoted in terms of temperature changes. Added heat causes a rise in average kinetic energy such that the molecules move faster and become hotter while reduction of heat makes them move less hence become cooler. A liquid that has reached the boiling point e.g., water at 100oC, could have constant temperature even with the addition of heat, and at this point, a gas and a liquid can coexist. The energy necessary to convert a kg of matter from liquid to gaseous state (or gas to liquid) is termed as the latent heat of vaporization (Jha, 2004).

How are they different?

Temperature is the measure of the kinetic energy of molecules that comprise a body. Heat, on the other hand, is a form of energy that is added into a body and is measured in joules. The addition of heat into a system is compared to adding energy, which is then expressed as a rise in the kinetic energy of the molecules present in the system. Heat aids in the change of state, such as evaporation and breaking of bonds holding the molecules together and does not alter the kinetic energy of a system. Therefore, the temperature cannot be described as energy but as being related to a system’s kinetic energy. When the average kinetic energy of particles rises i.e., increase in temperature, their average speed also rises, although not as a direct proportion (Jha, 2004).

What are the various properties of a substance that determine its heat capacity?

Heat capacity is the amount of heat necessary to alter the temperature of a body by one degree. It’s a measure that is expressed in Joules/Kelvin — adding heat to a body awards it with thermal energy, while some are transformed into kinetic energy and other as internal energy. The amount that is transformed into kinetic energy raises the temperature of the body. The heat added to a system, which is divided by the change in temperature is what is referred to as the heat capacity of a given body. Heat capacity is affected by the amount of sample expressed in mass as well as its kinetic energy. Large samples contain more heat capacity. The heat transferred (q), temperature change (ΔT) and heat capacity (C) are expressed as q = C ΔT = C (Tf – Ti) where Tf is the final temperature and Ti is the initial temperature and gives the temperature change (ΔT) (Jha, 2004).

What are the various sources of heat?

Heat can emanate from either natural or manmade sources. Some naturals sources include the sun, which generates solar energy essential to supports the life of various organisms. The earth also generates geothermal energy from hot springs and molten rocks from volcanoes. Fossil fuels such as coal are also combusted to generate heat. Artificial sources include electricity, which can be turned into heat, especially in industries. Moreover, heat is generated from machines, ignition, nuclear reactions, exothermic chemical reactions, and friction. Heat energy is generated when there is a transfer of heat from hotter to cooler bodies. Heat is very important in various day to day activities while various systems are used to derive it (Tillery et al., 2006.)


Burshstein, A.I. (2006). Introduction to Thermodynamics and Kinetic Theory of Matter. Weinheim: John Wiley and Sons.

Tillery, B. W., Enger, E. E., & Ross, F. C. (2008). SCI110: Integrated Science: 2009 Custom Edition. 4th Ed. New York: McGraw-Hill.

Jha, D.K. (2004). Text Book of Heat. New Delhi: Discovery Publishing House.