What is the average kinetic energy also known as?

• Define kinetic energy.
• Describe how temperature influences kinetic energy of particles.
• Define aboslute zero.

How much energy does it take to hit a baseball?

Kinetic energy is the energy of motion. Any object that is moving possesses kinetic energy. Baseball involves a great deal of kinetic energy. The pitcher throws a ball, imparting kinetic energy to the ball. When the batter swings, the motion of swinging creates kinetic energy in the bat. The collision of the bat with the ball changes the direction and speed of the ball, with the idea of kinetic energy being involved again.

As stated in the kinetic-molecular theory, the temperature of a substance is related to the average kinetic energy of the particles of that substance. When a substance is heated, some of the absorbed energy is stored within the particles, while some of the energy increases the motion of the particles. This is registered as an increase in the temperature of the substance.

Average Kinetic Energy

At any given temperature, not all of the particles of a sample of matter have the same kinetic energy. Instead, the particles display a wide range of kinetic energies. Most of the particles have a kinetic energy near the middle of the range. However, a small number of particles have kinetic energies a great deal lower or a great deal higher than the average (see Figure below ).

A distribution of molecular kinetic energies as a function of temperature. The blue curve is for a low temperature, while the red curve is for a high temperature.

The blue curve in the figure above is for a sample of matter at a relatively low temperature, while the red curve is for a sample at a relatively high temperature. In both cases, most of the particles have intermediate kinetic energies, close to the average. Notice that as temperature increases, the range of kinetic energies increases and the distribution curve “flattens out.” At a given temperature, the particles of any substance have the same average kinetic energy.

Absolute Zero

As a sample of matter is continually cooled, the average kinetic energy of its particles decreases. Eventually, one would expect the particles to stop moving completely. Absolute zero is the temperature at which the motion of particles theoretically ceases. Absolute zero has never been attained in the laboratory, but temperatures on the order of 1 × 10 -10 K have been achieved. TheKelvin temperature scale is the scale that is based on molecular motion and so absolute zero is also called 0 K. The Kelvin temperature of a substance is directly proportional to the average kinetic energy of the particles of the substance. For example, the particles in a sample of hydrogen gas at 200 K have twice the average kinetic energy as the particles in a hydrogen sample at 100 K.

Helium gas liquefies at 4 K or four degrees above absolute zero. Liquid helium is used as a coolant for large superconducting magnets and must be stored in insulated metal canisters.

• Kinetic energy is the energy of motion.
• At a given temperature, individual particles of a substance have a range of kinetic energies.
• The motion of particles theoretically ceases at absolute zero.

Questions

1. What is kinetic energy?
2. If the temperature increases, will particles move faster or slower that they would ata lower temperature?
3. What is absolute zero?
4. List one use for liquid helium.

• absolute zero: The temperature at which the motion of particles theoretically ceases.
• Kelvin scale: The scale that is based on molecular motion and so absolute zero is also called 0 K.
• kinetic energy: The energy of motion.

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Have you ever ridden a roller coaster? At the top of the tracks, the roller coaster car does not have kinetic energy because it is at rest. As it goes down, its kinetic energy slowly increases with its speed. Similarly, when a person rides a bicycle, it possesses kinetic energy. As the bicycle's velocity increases, so does its kinetic energy. A running person, a speeding bullet all have kinetic energy.

Kinetic energy (K.E.) is the energy possessed by an object in motion. Now, let’s understand kinetic energy and its dependence on other factors like temperature in more detail.

KINETIC ENERGY AND TEMPERATURE

According to the kinetic-molecular hypothesis, a substance's temperature is proportional to the average kinetic energy of its particles. When a substance is heated, some of the energy absorbed is kept inside the particles, while another energy accelerates particle motion. This is manifested as a rise in the material's temperature.

When studying kinetic energy in gas molecules and its relationship with temperature, we generally define the term ‘average kinetic energy.

AVERAGE KINETIC ENERGY:

The average kinetic energy of a gas molecule is defined as the product of half of the mass of each gas molecule and the square of the RMS speed. Mathematically, it's as follows:

m is the mass

vᵣₘₛ is the RMS velocity

K is the average kinetic energy

RELATION BETWEEN AVERAGE KINETIC ENERGY AND TEMPERATURE:

The temperature of a substance is directly proportional to the average kinetic energy of the substance particles. Because the mass of these particles is constant, the particles must move faster as the temperature rises.

Here’s a simple experiment to help you understand👇:

• Take two beakers, one with hot water and another with cold water.
• Add a few drops of any dye in both beakers.
• We observe that the dye particles in hot water show faster movement than those in cold water. The particles in both the beakers move at different speeds; they have different kinetic energies.
• We can conclude that the particles in the hotter body have a comparatively larger average K.E. than the colder one. In this way, the average K.E. of particles is indicated by their temperature.

We have seen the effect of increasing temperature on kinetic energy. Now let’s discuss the possibility of decreasing the temperature of the system and its effect on kinetic energy.

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The kinetic energy of a particle decreases as we lower the system's temperature. But imagine we keep decreasing the temperature and reach absolute zero. Then what happens to kinetic energy?

ABSOLUTE ZERO:

• Absolute zero on the Celsius scale is −273.15℃. The Kelvin scale is based on absolute zero and starts at 0K.
• Absolute zero is where the kinetic energy of the particles is zero. That means all the motion between particles will cease.

CONCLUSION:

• Kinetic energy is the energy possessed by an object in motion.
• The temperature of a substance is directly proportional to the average kinetic energy of the substance particles.
• Absolute zero is where the kinetic energy of the particles is zero.

FAQs:

1. What happens at absolute zero?

At absolute zero, the thermodynamic system has the lowest temperature, and the K.E of the particles is zero.

2. What temperature is absolute zero in Fahrenheit?

Absolute zero corresponds to −459.67℉ in the Fahrenheit scale.

3. What is the lowest temperature achieved?

−273.144℃ is the lowest temperature that we achieved in the laboratory.

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