Have you ever wondered why some objects feel hot and some feel cold? Or why water boils when heated and freezes when cooled? The answer lies in the concept of temperature and how it is related to the kinetic energy of the particles that make up matter.
Contents
What is Kinetic Energy?
Kinetic energy is the energy of motion. Any object that is moving possesses kinetic energy. For example, a baseball has kinetic energy when it is thrown by a pitcher, a car has kinetic energy when it is driving on the road, and a bullet has kinetic energy when it is fired from a gun.
But what about the objects that seem to be at rest, like a book on a table or a glass of water? Do they have kinetic energy too? The answer is yes, they do. But not in the same way as the objects that are visibly moving.
What is Temperature?
Temperature is a measure of the average kinetic energy of the atoms or molecules in a substance. Atoms and molecules are the tiny building blocks of matter that are too small to see with our eyes. They are constantly in motion, vibrating, rotating, and colliding with each other. This motion creates kinetic energy within the substance.
The more kinetic energy the atoms or molecules have, the higher their temperature. The less kinetic energy they have, the lower their temperature. This is why hot objects appear to be in constant motion and give off radiant energy, while cold objects appear to be still and absorb energy.
How are Temperature and Kinetic Energy Related?
The relationship between temperature and kinetic energy is simple: as the temperature of a substance increases, the average kinetic energy of its particles also increases. This means that the particles move faster and collide more frequently and forcefully with each other. As the temperature of a substance decreases, the average kinetic energy of its particles decreases. This means that the particles move slower and collide less often and less intensely with each other.
This relationship can be expressed mathematically by using the Kelvin temperature scale, which is based on molecular motion. The Kelvin temperature scale starts at absolute zero, which is the theoretical temperature at which all molecular motion ceases. Absolute zero has never been attained in the laboratory, but temperatures close to it have been achieved. Absolute zero is equal to 0 K or −273.15 °C.
The Kelvin temperature of a substance is directly proportional to the average kinetic energy of its particles. This means that if we double the Kelvin temperature of a substance, we also double its average kinetic energy. If we halve the Kelvin temperature of a substance, we also halve its average kinetic energy.
How does Temperature Affect the State of Matter?
The state of matter of a substance depends on how closely its particles are packed together and how much they can move around. There are three common states of matter: solid, liquid, and gas.
- In a solid, the particles are tightly packed together in a fixed shape and position. They can only vibrate slightly around their fixed points. Solids have low kinetic energy and low temperature.
- In a liquid, the particles are loosely packed together in a variable shape but fixed volume. They can slide past each other and flow freely. Liquids have moderate kinetic energy and moderate temperature.
- In a gas, the particles are widely spaced apart in a variable shape and volume. They can move randomly and rapidly in all directions. Gases have high kinetic energy and high temperature.
When we heat or cool a substance, we change its temperature and therefore its average kinetic energy. This can cause the substance to change its state of matter by undergoing phase transitions.
- When we heat a solid, we increase its kinetic energy until it reaches its melting point, which is the temperature at which it changes into a liquid.
- When we heat a liquid, we increase its kinetic energy until it reaches its boiling point, which is the temperature at which it changes into a gas.
- When we cool a gas, we decrease its kinetic energy until it reaches its condensation point, which is the temperature at which it changes into a liquid.
- When we cool a liquid, we decrease its kinetic energy until it reaches its freezing point, which is the temperature at which it changes into a solid.
Conclusion
Temperature and kinetic energy are two different but closely related concepts that explain how matter behaves at different levels of heat and coldness. Temperature is a measure of the average kinetic energy of the atoms or molecules in a substance. Kinetic energy is the energy of motion of those particles. As the temperature of a substance increases or decreases, so does its average kinetic energy. This affects how fast or slow the particles move and how strongly or weakly they interact with each other. This also affects how tightly or loosely they are packed together and what state of matter they form: solid, liquid, or gas.
References
- According to Khan Academy, heat is thermal energy transferred from a hotter system to a cooler system that are in contact.
- According to Chemistry LibreTexts, the Kelvin temperature scale is the scale that is based on molecular motion, and so absolute zero is also called 0 K.
- According to Relationship Between, the relationship between temperature and kinetic energy is simple: as the temperature of an object increases, the average kinetic energy of its particles also increases.
- According to Unacademy, individual molecules do not have a temperature; they have kinetic energy. Populations of molecules have a temperature linked to their average velocity.
