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Melting Point/Freezing Point ​ ​ The specific temperature at which a substance changes from a solid to a liquid state (melting) or from a liquid to a solid state (freezing).

2 construct and interpret a reaction pathway diagram, in terms of the enthalpy change of the reaction and of the activation energy A Level Chemistry CIE Constructing and interpreting a reaction pathway diagram allows us to visualize the energy changes that occur during a chemical reaction. This diagram, also known as an energy profile or reaction energy diagram, illustrates the progression of a reaction from reactants to products along the reaction pathway. The vertical axis of the reaction pathway diagram represents the energy content of the system, typically measured in terms of enthalpy (H). The horizontal axis represents the progress of the reaction from left to right, going from the reactants to the products. The diagram includes three key components: the reactants, the products, and the energy changes that occur during the reaction. The enthalpy change (∆H) of the reaction is represented by the difference in energy between the reactants and the products. If the reactants have a higher enthalpy than the products, the ∆H value is negative, indicating an exothermic reaction. Conversely, if the products have a higher enthalpy than the reactants, the ∆H value is positive, indicating an endothermic reaction. On the reaction pathway diagram, the enthalpy change (∆H) is shown as the vertical distance between the energy levels of the reactants and products. For an exothermic reaction, the products' energy level is lower than that of the reactants, resulting in a negative ∆H. In contrast, for an endothermic reaction, the products' energy level is higher, leading to a positive ∆H. Additionally, the reaction pathway diagram illustrates the activation energy (Ea) of the reaction. The activation energy represents the energy barrier that must be overcome for the reaction to proceed. It is the minimum energy required for the reactant molecules to reach the transition state and form the products. On the reaction pathway diagram, the activation energy is shown as the energy difference between the reactants and the highest energy point on the reaction pathway, known as the transition state or the activated complex. The activation energy determines the reaction rate and influences the speed at which the reaction occurs. By examining the reaction pathway diagram, we can interpret various aspects of the reaction. The height of the energy barrier (activation energy) indicates the difficulty of the reaction. A higher activation energy implies a slower reaction rate, while a lower activation energy suggests a faster reaction. The overall enthalpy change (∆H) can be calculated by comparing the energy levels of the reactants and products. It represents the difference in energy content between the initial and final states of the system. The enthalpy change, along with the activation energy, provides valuable insights into the energy profile and kinetics of the reaction. Understanding and interpreting a reaction pathway diagram allows chemists to analyze the energy changes involved in a reaction. It helps predict the feasibility, rate, and overall energy requirements of the reaction. By examining the enthalpy change and activation energy, we can gain a deeper understanding of the reaction's thermodynamics and kinetics. In summary, constructing and interpreting a reaction pathway diagram enables us to visualize and analyze the energy changes and activation energy of a chemical reaction. The diagram provides insights into the enthalpy change (∆H) between reactants and products, as well as the energy barrier required for the reaction to occur. By examining these components, we can assess the reaction's energy profile, feasibility, and rate, enhancing our understanding of chemical kinetics and thermodynamics.

Writing Equations Grade 10 SABIS SABIS Including the energy required or released

Health and safety issues related to Rate of reaction SABIS Grade 10 SABIS ​ Increasing the surface area of solid (by reduction of particle size) may cause explosion in some cases. For example  In flour mills, the air can fill with fine flour dust which has very large surface area. A spark can cause the flour to catch fire and explode.  In coal mines where the air is filled with very fine coal dust.

Know that an α particle is the nucleus of a helium atom Grade 10 SABIS ​ An α particle, often denoted as ^4He, is a fundamental subatomic particle that serves as the nucleus of a helium atom. It is composed of two protons and two neutrons, giving it a mass number of 4 and an atomic number of 2. The α particle is named after the Greek letter α (alpha) due to its historical significance in early studies of radioactivity and nuclear physics. Being the nucleus of a helium atom means that the α particle carries the essential components responsible for the atom's identity. It contains the positively charged protons, which determine the atomic number and chemical properties of the helium atom. The presence of two protons in the α particle gives it a net positive charge of +2, balancing the negatively charged electrons surrounding the nucleus in a helium atom. The α particle is highly stable due to its tightly bound configuration of protons and neutrons within the nucleus. This stability contributes to its occurrence in various nuclear reactions and natural processes. In certain radioactive decays, such as alpha decay, a parent nucleus emits an α particle, reducing its atomic number by 2 and its mass number by 4. This emission results in the formation of a daughter nucleus with a different atomic identity. The α particle possesses unique properties that distinguish it from other subatomic particles. It has a relatively large mass compared to other particles and can penetrate matter to a limited extent due to its charge and mass. In practical applications, α particles are commonly used in radiation detectors and nuclear research. Their distinctive properties make them useful for studying particle interactions, measuring radiation levels, and investigating the properties of atomic nuclei. Understanding that an α particle is the nucleus of a helium atom is fundamental to comprehending the structure of matter and the behavior of subatomic particles. It allows us to appreciate the role of α particles in nuclear processes and their significance in the overall composition of atoms. In summary, an α particle serves as the nucleus of a helium atom, consisting of two protons and two neutrons. It carries a net positive charge of +2 and possesses unique properties that distinguish it from other subatomic particles. Recognizing the α particle as the nucleus of a helium atom contributes to our understanding of atomic structure, nuclear reactions, and radiation phenomena.

Know what is meant by electrical work Grade 10 SABIS ​ Electrical work in thermochemistry refers to the work done by or on a system as a result of the flow of electrical charges. It involves the transfer of energy through an electrical circuit and can have significant implications in various chemical and physical processes. When an electric current passes through a conductor, such as a wire, it involves the movement of charged particles, typically electrons. This movement of charges constitutes an electric current and results in the generation of electrical work. The electrical work done can be expressed mathematically using the equation W = IVt, where W represents the work done, I is the electric current, V is the potential difference (voltage), and t is the time over which the current flows. The magnitude of the electrical work done is determined by the product of the current, voltage, and time. A higher current or voltage, or a longer duration of current flow, results in a greater amount of electrical work. In thermochemistry, electrical work is particularly relevant in processes involving electrolysis, where chemical reactions are driven by the passage of an electric current. It is also significant in electrochemical cells, batteries, and other energy storage and conversion devices. For example, in the electrolysis of water, an electric current is passed through water, causing the water molecules to undergo a chemical reaction and separate into hydrogen and oxygen gases. The electrical work done in this process is required to drive the reaction and facilitate the decomposition of water. Understanding electrical work in thermochemistry enables the analysis of energy transformations and conversions involving electrical energy. It provides insights into the relationship between electricity and chemical reactions, and it plays a crucial role in various technological applications. It's important to note that electrical work is just one component of the overall energy changes in a system. It should be considered in conjunction with other forms of work, such as pressure-volume work or shaft work, to fully account for the total energy involved in a process. In summary, electrical work in thermochemistry refers to the work done by or on a system as a result of the flow of electrical charges. It involves the transfer of energy through an electrical circuit and is determined by the current, voltage, and time. Understanding electrical work is essential for analyzing energy transformations in electrochemical processes and other electrical applications.

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Positron Grade 10 SABIS ​ The positron has the same mass as an electron but has a charge of 1+ is a subatomic particle that is similar to an electron in terms of mass but possesses a positive charge. It is often denoted as e+ and is considered the antiparticle of the electron. Despite having the same mass as an electron, the positron has an opposite charge of +1. Both the electron and the positron are classified as leptons, which are fundamental particles with no internal structure. They are part of the family of elementary particles in the Standard Model of particle physics. The mass of an electron and a positron is approximately 9.11 x 10^-31 kilograms. This mass is incredibly small, making electrons and positrons highly lightweight particles. The key difference between an electron and a positron lies in their electric charge. While an electron carries a negative charge of -1, the positron carries an equal but opposite positive charge of +1. The charges of the electron and the positron determine their behavior in electromagnetic interactions. Due to their opposite charges, electrons and positrons are attracted to each other and can undergo annihilation when they collide. When an electron and a positron collide, their charges cancel out, resulting in the production of energy in the form of gamma rays. This process is known as electron-positron annihilation. The existence of positrons was first theorized by Paul Dirac in 1928 and was later confirmed through experimental observations. The discovery of the positron contributed to the development of antimatter physics and had significant implications for our understanding of particle interactions. In practical applications, positrons have various uses, including in medical imaging techniques such as positron emission tomography (PET). In PET scans, positrons emitted by a radioactive substance interact with electrons in the body, leading to the detection of gamma rays and providing information about physiological processes. The study of particles like electrons and positrons is crucial in understanding the fundamental building blocks of matter and the intricate workings of the universe at the subatomic level. Advances in particle physics have led to numerous technological innovations and have broadened our knowledge of the fundamental laws governing the physical world. In summary, a positron shares the same mass as an electron but possesses a positive charge of 1+. Both particles are leptons, with the electron carrying a negative charge of -1. The existence of positrons was theorized and later confirmed through experimental observations. Understanding the properties and behavior of electrons and positrons contributes to our knowledge of particle physics and has practical applications in various fields, such as medical imaging.

Cooling Curve ​ ​ A graphical representation of the relationship between temperature and time as a substance cools.

The rate of the reaction can be defined as either: Grade 10 SABIS ​ The quantity of products produced per unit time OR the quantity of reactants consumed per unit time.

Microscopic changes that take place when a solid is warmed Grade 10 SABIS ​ When a solid is warmed in thermochemistry, several microscopic changes occur at the molecular level. These changes involve the increased kinetic energy of the solid's constituent particles and their interactions, leading to observable macroscopic effects such as expansion, changes in lattice structure, and phase transitions. As the solid is heated, the temperature of the system rises, and this increase in temperature corresponds to an increase in the average kinetic energy of the solid's particles. The particles, which may be atoms, ions, or molecules, gain energy and vibrate more vigorously around their fixed positions within the solid's lattice structure. The increased kinetic energy causes the intermolecular or interatomic forces within the solid to weaken. These forces, such as ionic bonds, metallic bonds, or covalent bonds, hold the particles together in a highly organized lattice arrangement. As the particles gain energy, the forces become less effective at maintaining the lattice structure's rigidity. The weakened intermolecular or interatomic forces result in thermal expansion of the solid. The increased vibrational motion of the particles causes them to move slightly farther apart, leading to an increase in volume. This expansion is commonly observed when solids are heated. In addition to expansion, the increased kinetic energy can lead to changes in the lattice structure of the solid. For example, in some cases, the solid may undergo a phase transition from one crystal structure to another as the temperature increases. This transition involves rearrangements of the particles within the lattice, resulting in a change in the solid's physical properties. Furthermore, at higher temperatures, some solids may undergo melting, where the particles gain sufficient energy to overcome the intermolecular or interatomic forces completely. This transition from a solid to a liquid phase involves the disruption of the lattice structure and the conversion of the solid into a mobile liquid state. It's important to note that the microscopic changes in a solid being warmed are reversible. When the solid is cooled, the particles lose kinetic energy, and the intermolecular or interatomic forces regain their effectiveness, leading to a decrease in volume and a return to the initial state. Understanding the microscopic changes that occur when a solid is warmed is crucial in thermochemistry and various applications. It allows us to analyze energy transfers, phase transitions, and the behavior of substances under different temperature conditions. In summary, when a solid is warmed in thermochemistry, microscopic changes take place at the molecular level. The increased kinetic energy of the particles weakens the intermolecular or interatomic forces, resulting in expansion, changes in lattice structure, and, in some cases, phase transitions. Recognizing and studying these microscopic changes enhances our understanding of energy transfer and the behavior of solids at different temperatures.

Reaction of alkali metal hydride with water: Grade 10 SABIS ​ Generally: MH(s) + H2O(l) → M+ (aq) + OH- (aq) + H2(g) Observations for the reaction of alkali metal hydride with water: Evolution of a gas that burns with a squeaky pop sound with a lit splint.