Tag: Pressure

Introduction

The whole universe is composed of two parts; system and surroundings. There occurs an exchange of heat between the system and the surroundings. Thermodynamics tells us about the exchange of heat, different forms of energy, and the transformation of energy into work. It also explains some other properties of the system like temperature, pressure, density, enthalpy, entropy, etc.

Define Thermodynamics

Thermodynamics is a topic that derives the relationship between heat, energy, work, and temperature. According to thermodynamics, if the system does the work then its value will be negative and when work is done on the system its value will be positive.

Difference between Thermodynamics and Statistical Mechanics

Define System and Surroundings

System: The part of the universe in which all the matter remains is known as a system. 

Surroundings: The other part of the universe outside the system is known as the surroundings. The system and surroundings are divided by a boundary.

Classification of the system:

1. Open system: It has the capacity to exchange both energy and matter with the surroundings. In an open system, both the temperature T and pressure P are constant. For example, the human body.
2. Closed system: This system only exchanges energy with the surroundings. The entropy of a closed system is always constant. For example, water boils using a closed lid.
3. Isolated system: It exchanges neither matter nor energy with the surroundings. For example, a thermos flask is an example of an isolated system. 

Different types of processes in thermodynamics

• Isothermal process: In this process, the temperature (T) of the system is always constant.

1. Isochoric process: Here, the volume (V) of the system is always constant.
2. Isobaric process: In this process, the pressure (P) of the system remains constant.
3. Adiabatic process: In this process, the change in heat (Q) with the surroundings is zero.

Properties of thermodynamics

1. Intensive properties: These properties don’t change with the change in the amount of matter. For example boiling point, melting point, density, etc.
2. Extensive properties: These properties highly depend on the amount of matter in the system. For example mass, volume, etc.

Functions in thermodynamics

1. State functions: These functions change with the change in the state of a system. For example Enthalpy (H), internal energy (U), entropy(S), and density (d). 
2. Path functions: Heat (Q) and work (W) don’t depend on the state of a system, but rather depend on the path of a system. They are called path functions.

Define Enthalpy and Entropy

Enthalpy (H): It is a property of thermodynamics that indicates the overall heat capacity of a system. It is expressed by the sum of the system’s internal energy and the product of the pressure and volume of the system. 

H = U + PV

Depending on the symbol before the value of enthalpy, any reaction can be classified into two parts.

• Exothermic reaction: The reaction is called exothermic when heat is generated during a reaction. The value of enthalpy in an exothermic reaction is always negative.
• Endothermic reaction: When the system absorbs energy from the surroundings to execute a reaction is called an endothermic reaction.  The value of enthalpy in an exothermic reaction is always positive.

Entropy (S): It measures the extent of disorderness of a system. For a spontaneous reaction, entropy S is always negative and for a non-spontaneous reaction, entropy S is always positive.

Thermodynamic potential

Thermodynamic potentials are used to define a particular state of the system. They are internal energy (U), enthalpy (H), Gibbs free energy (G), and Helmholtz free energy (F).

Laws of thermodynamics

• Zeroth law: This law states: “if two bodies A and B are each in thermal equilibrium with some third body C, then they are also in equilibrium with each other.”
• First law: This law states:  “Energy can neither be destroyed nor be created, it can only be transferred from one form to another”. It is also called the “Law of conservation of energy.”

ΔQ = ΔU + W

ΔQ= Change in heat of a system.

ΔU = Change in internal energy of a system.

W = Work done

• Second law: This law states: “any spontaneously occurring process will always lead to an escalation in the entropy (S) of the universe.”

\[\Delta {S_{Total}} = {\rm{ }}\Delta {S_{system}} + {\rm{ }}\Delta {S_{surroundings}} > {\rm{ }}0\]

• Third law: This law states: “the entropy of a system approaches a constant value as the temperature approaches absolute zero.”

\[{S_{T = 0}} = 0\]

Daily life examples of thermodynamics

1. Human bodies sweat, producing heat from the body.
2. Melting of ice cubes.
3. Like A thermodynamic system, the human body exchanges mass and energy with the surroundings.

Summary

A type of heat energy that connects with other types of energy is called thermodynamics. Heat or work are two ways that energy is changed or exchanged. In thermodynamics, there are four processes. They are isothermal, adiabatic, isobaric, and isochoric. Thermodynamics explains many important properties of the system. Energy is the dominant focus of thermodynamics which is how it is used and transforms from one state to another. Thermodynamics frequently includes using heat to generate work like in the engines of automobiles and generating work to transfer heat like in the refrigerator.

Frequently Asked Questions 

1. Why does thermodynamics emphasize energy?

Ans: The first law of thermodynamics defines that the total energy of the system is always conserved. Neither energy can be created nor destroyed. It is only capable to change from one type to another. Like, in the combustion of fuel the chemical energy is transformed into thermal energy.

2. Why is it referred to as free energy?

Ans: Because it is readily accessible at all times, Gibb’s free energy is known as free energy. If necessary, the reaction can obtain this energy without exerting any effort.  Enthalpy (H) and also the product of the system’s temperature (T) and entropy(S) are added to determine the change in Gibbs free energy (G).

G = H +TS

3. What are the drawbacks of thermodynamics?

Ans: Thermodynamics can’t explain any properties of the system quantitatively. It doesn’t include the direction of the flow of heat. It can’t tell anything about the spontaneity of any reaction. These are the drawbacks of thermodynamics.

Introduction

The measurement of a system or substance’s heat is called its temperature. The pace of an enzyme-catalyzed reaction typically increases as the temperature rises in most chemical processes. Temperature is the internal energy contained within a particular system. Temperature can be measured by a thermometer. Temperature is measured in degrees Celsius, which is written as °C, and can be also measured in Kelvin (K) and Fahrenheit (°F). Temperature alters the states of matter by reducing or increasing the interatomic distances. 

Temperature Effect/Effect of Temperature

In several ways, the temperature has an impact on substances, processes, and enzymes. A substance’s state can be altered by varying its temperature. As the temperature rises, a solid can turn into a liquid, and as the temperature rises more, a liquid can turn into a gas. At high temperatures, a solid can be directly converted into a gas and this process is known as sublimation. Similar to the process where liquids may turn into solids at low temperatures, gases can become liquids by raising pressure while lowering the temperature. The rate of response of the transformation between the different states of matter is also positively or negatively impacted by temperature.

Learn More about Temperature and Heat. Check out more videos in 7th Class Science Lesson no 4.

The Effect of Change of Temperature on Solid State

As the temperature rises, the particles’ kinetic energy rises as well. As a result of the increase in kinetic energy, particles move faster and begin vibrating more quickly. The forces of attraction between the particles are weakened or eliminated by the heat energy. The particles start to travel more freely after leaving their fixed places. At some point, the solid melts and becomes a liquid. The melting point of a solid is the temperature at which it begins to dissolve into a liquid. When two distinct solid objects formed of the same substance are melted, they might combine to form a new one, a process known as fusion.

Effect of Change of Temperature on States of Matter

Heating and cooling are the two primary methods for converting states of matter. By applying heat, a solid can be transformed into a liquid. Similar to how a liquid may become a gas by heating. The opposite is also true; when a gas loses any of its thermal energy, it turns into a liquid. Further, removing a liquid causes its heat energy to solidify. The rising temperature causes a rise in the kinetic energy of the particles and the interspace between them. The force of attraction between particles is reduced by the increase in kinetic energy. 

Effect of Temperature on Pressure

A physical force that is applied to an item by anything in touch with it is called pressure. The pressure can be estimated by the force per unit area. Three variables which affect how much pressure a gas exerts on the walls of the chamber of a container in which it is contained and surrounded by a vacuum. These factors are the quantity of gas within the chamber, the chamber’s size, and the gas’s temperature. The link between the pressure and temperature of gases can be explained, according to the gas law, which states that the pressure of a given volume of a specific gas is precisely proportional to its temperature at a constant volume. This relationship between pressure and temperature is what is meant by the term “pressure-temperature relationship.” It can be modelled as:

  P∝T

A system’s temperature changes cause the molecules in the gas to move more quickly, increasing the pressure on the gas container’s wall. The system’s pressure rises as a result. The pressure likewise lowers when the system’s temperature rises. As a result, for constant volume, the pressure of a given gas is exactly proportional to the temperature.

The gas expands in volume at constant pressure as the temperature rises. The volume of the gas grows because it requires more space to move since the kinetic energy of the molecules increases as the temperature rises.

Effect of Temperature-Examples

The usage of light sticks or glow sticks is one illustration of how temperature affects the speed of chemical reactions. Chemiluminescence, a chemical process, occurs on the light stick. But neither is needed for nor produced by this reaction. The temperature has an impact on its pace. Precipitation reaction, activation energy, etc. are further examples.

Summary

The many states of matter are significantly impacted by temperature. The impact of temperature varies depending on the condition of matter. The kinetic energy of the state increases with temperature, yet the force of attraction varies depending on the state. The various states of matter are also impacted under constant pressure and volume. The pressure of the gas drops while the volume remains constant. The volume of the gas grows with constant pressure.

Frequently asked questions

1. What is the Liquid State of Matter?

Ans: Between the solid and gaseous forms of matter is the liquid state. Ice (solid), liquid as water, and gas as vapor are the three states of water. Although liquids do not have particular shapes, they do have specific volumes. The force of attraction in the liquid state is stronger than that in the gaseous state and weaker than that in the solid state. Atoms in this state have kinetic energies that are higher than those in solids, but lower than those in gases.

2. What Happens when the Temperature of a Gas Increases at Constant Pressure?

Ans. The temperature of a given system or gas container rises as the pressure in that system or container rises. While the pressure remains constant, the temperature rises, the velocity of the gas molecules increases, and the volume of the gas rise. As the gas’ temperature rises, the gas ascends into the atmosphere.

3. What is the Relationship between Pressure and Volume in Boyle’s Law?

Ans: When the temperature is maintained constant, Boyle’s Law states that the pressure exerted by a certain quantity of gas (the number of moles) is inversely proportional to the volume. The volume of the gas reduces with increasing pressure, and vice versa. The molecule tends to approach.

Introduction

Pressure can be defined as the force exerted perpendicularly per square unit of area of any object. It is represented by the formula,                                                                                                                        

                                                             P = F ⁄ A

where P is the pressure, F is the force exerted on the object, and A is the area of the object. Pressure is measured in pascal, and is classified into absolute, atmospheric, differential, and gauge pressure. A change in pressure has different effects on different states of matter.

Change in Pressure

Since the pressure exerted on an object is the amount of force applied per unit area of that object, a change in area or a change in the amount of exerted force can result in a change in pressure. For example, if the surface area decreases, the pressure increases simultaneously when the surface area decreases, the pressure decreases provided that the force applied remains constant. 

Effect of Pressure on the States of Matter

Pressure change can have different effects on different states of matter. By exerting pressure on the matter particles, we can draw them closer. Therefore, applying pressure can cause liquids to turn into solids, and when pressure is applied to a gas that is contained in a cylinder, the gas begins to compress and turn into a liquid. As pressure rises, the volume of the gas reduces, which causes the gas to change into a liquid and then finally a solid. The volume of a gas is inversely related to its pressure and directly relates to the number of molecules it contains.

Pressure has less of an impact on solids because they are non-compressible forms of matter. By applying pressure and lowering the temperature, liquids can be transformed into solids.

Effect of Pressure on Equilibrium

The equilibrium will adjust to minimize a change in the pressure of a gaseous reaction mixture. If the pressure is raised, the equilibrium will change to favour a fall in the pressure. The equilibrium will change if the pressure is reduced to favour an increase.

When a system’s volume is reduced, the pressure will rise (and the temperature is constant). A greater number of collisions occur with the container’s walls. There will be fewer collisions and hence less pressure if there are fewer gas molecules. The equilibrium will change in a way that reduces the number of gas molecules, which will likewise reduce the pressure. To forecast which way equilibrium will shift in response to a change in pressure, we must consider how many gas molecules are involved in the balanced reactions.

For example, the chemical reaction between nitrogen and hydrogen is shown below:

                                                           N2 (g) + 3H2 (g)→ 2NH3↑

The proportion in the equation that balances is 1:3:2. In other words, the 1N2 molecule combines with the 3H2 molecule to produce NH3 gas (from the balanced equation). Four molecules of reactant gas must therefore be present to produce two molecules of product gas.

• Pressure buildup will favour the reaction which results in fewer gas molecules. Because there are fewer product gas’ molecules, the forward reaction is more advantageous. Due to the rightward shift in equilibrium, the yield of NH3 will rise.
• The reaction that produces more gas molecules will be more favourable as pressure drops. If there are more reactant gas molecules present, the reverse reaction is more favourable. As a result of the equilibrium shifting to the left, the yield of NH3 will decline.

Some Facts

• Pressure is directly proportional to the temperature.
• In contrast to solids and liquids, gases are more easily subjected to pressure.
• Compared to gases, solids and liquids are less sensitive to pressure.
• When air pressure is raised, the boiling point of water rises.
• The equilibrium will adjust to minimize the change in pressure of the gaseous mixture.

Frequently Asked Questions

1. Does Changing the Size of the Container Affect the Pressure?

Ans: No change in concentration could change the pressure if the equilibrium reaction does not involve a change in the number of molecules in the gas phase. Therefore, altering the container’s size without also altering the pressure would have no impact on the reaction. The number of molecules stays constant and applies the same pressure whether the container size decreases or grows.

2. How can the Physical Condition of the Matter be Altered?

Ans: It is also possible to change the physical state of matter by adjusting the pressure that is applied. For example, by applying pressure and lowering the temperature, gases can liquefy. 

3. How does Pressure Affect the Boiling Point of a Liquid?

Ans: All liquids evaporate with an expansion. The expansion and delay of vaporization are the results of pressure on the surface. As a result, when pressure is applied, the boiling point rises.