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**Kinetic Theory of Matter**

Originally created by Emily Adamson Edited by M.Elizabeth

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**What’s the Kinetic Theory of Matter?**

It’s a theory that helps explain difference between the states of matter.

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**The Kinetic Theory of Matter states…**

Matter is made up of constantly moving molecules or atoms.

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**Under the Kinetic Theory of Matter…**

Solids’ particles are so close to each other that they only vibrate in place.

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**Under the Kinetic Theory of Matter…**

Liquids’ particles have more space to move than solids, but there is still an attraction between them.

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**Under the Kinetic Theory of Matter…**

Gases’ particles are far apart and move around because the attraction is so low it can be disregarded.

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**Substances can change into different phases of matter and back.**

WHY DOES THIS HAPPEN?

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**First, we need to know about….**

Kinetic Energy is energy of motion. There are multiple forms, such as: Vibrational Rotational Translational.

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**First, we need to know about….**

Thermal energy is total kinetic energy of all of a substance’s atoms and molecules . Kinetic Energy

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**First, we need to know about….**

Temperature is the average amount of kinetic energy in an object.

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Matter can change into different phases because the exchange of thermal energy between a substance and the environment. Forces that hold substances in one phase are overcome with the addition of energy

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**Everything wants to be in its lowest state of energy**

Everything wants to be in its lowest state of energy. That’s why the exchange occurs!

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**Increases as temperature increases **

Thermal Energy Increases as temperature increases Increases as kinetic energy increases Temperature Increases as thermal energy increases Kinetic Energy Motion increases as temperature increases

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**THEY’RE ALL INTERTWINED!**

Overall, when temperature increases, atoms and molecules’ motion increases (kinetic energy). Thermal energy increases because the total amount of kinetic energy increased due to the temperature change. THEY’RE ALL INTERTWINED!

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**KINETIC THEORY OF MATTER**

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3 STATES OF MATTER SOLID LIQUID GAS

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**SOLIDS Fixed shape and volume Normally hard and rigid**

Large force needed to change shape High density Incompressible

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**Model of Solids Closely packed together Occupy minimum space**

Regular pattern Vibrate about fixed position Not free to move about

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LIQUIDS Fixed volume but no fixed shape High density Not compressible

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Model of Liquids Occur in clusters with molecules slightly further apart as compared to solids Free to move about within confined vessel

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GASES No fixed shape or volume Low density Compressible

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**Model of Gases Very far apart Travel at high speeds**

Independent and random motion Negligible forces of attraction between them

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**Brownian Motion Movement of smoke under the microscope Random motion**

High concentration to low concentration until uniform (all the same = homogeneous) Increases with increasing temperature (thermal energy)

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**Pressure in Gases (Ideal Gases)**

Air molecules in a container are in as state of continuous motion.

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**Pressure in Gases (Ideal Gases)**

Air molecules in a container are in as state of continuous motion. When they collide with the wall of a container, they exert a force, F on the wall. F

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**Pressure in Gases (Ideal Gases)**

Air molecules in a container are in as state of continuous motion. F When they collide with the wall of a container, they exert a force, F on the wall. The force per unit area is the pressure exerted on the wall.

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**Pressure-volume (p-V) relationship of a gas**

Air molecules in a container will exert a certain amount of pressure.

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**Pressure-volume (P-V) relationship of a gas**

Air molecules in a container will exert a certain amount of pressure. If the volume of this container was to decrease, the air molecules will have less space to move about. This will result in the molecules colliding with the walls more frequently.

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**Pressure-volume (p-V) relationship of a gas**

Therefore, when we decrease the volume of the container, the pressure exerted by the air molecules on the container increases.

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**p1V1 = p2V2 p = k/V pV = k (k is a constant)**

To form an equation, p = k/V pV = k (k is a constant) p1V1 = p2V2 Where p1 and V1 are the initial pressure and volume, And p2 and V2 are the final pressure and volume.

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**(600)(1500) = p2(1000) p2= p2= 900 Pa Example:**

The volume of a fixed mass of gas at 600 Pa is 1500cm3. What is the pressure if the volume is reduced to cm3 at constant temperature? Solution: Using the formula: p1V1 = p2V2 (600)(1500) = p2(1000) p2= p2= 900 Pa

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P-T Relationship Now we will keep the volume of the container constant. We will investigate to see how the pressure will vary with temperature of the gas.

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**Pressure increases as the temperature increases.**

P-T Relationship From the applet, we can see that Pressure increases as the temperature increases. when the volume is kept constant

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Example Air is being trapped in a container of fixed volume. At room temperature of 300 K, the pressure exerted by the gas is 100 Pa. If the air in the container was heated to 600 K, what is the new pressure exerted by the gas now? Solution: Since pressure is proportional to temperature, when temperature increases, pressure should also increase. Temperature increases by 2 times, so pressure should increase by 2 times. New pressure = 100 x 2 = 200 Pa

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**V-T Relationship at constant pressure**

This is the most commonly occurring relationship. When gas gets heated, the amount of space that it occupies expands. So when temperature increase, volume would also increase. Temperature is proportional to volume. at constant pressure

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Example A balloon is filled with gas, at a temperature of 300 K, to a volume of 50cm3. If I want to expand the balloon to a volume of 150cm3, what is the temperature of the gas now? Assuming that the pressure exerted by the gas does not change. Solution: Volume is proportional to temperature. Since the volume has to be increased by 3 times, the volume should also be increased accordingly. Required temperature = 300 x 3 = 900 K

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