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Boiling water until it evaporates, then condensing the steam Grade 10 SABIS SABIS Physical

Vaporization of ethanol Grade 10 SABIS SABIS Endothermic

STP (Standard Temperature and Pressure) Grade 10 SABIS SABIS A set of conditions (0°C and 1 atm) used as a reference for gas laws and other calculations.

Heating wax until it melts Grade 10 SABIS SABIS Physical

Standard Temperature and Pressure (STP) Grade 10 SABIS SABIS 0⁰C and 1.00 atm pressure

Know the meaning of the term “calorimetry” in SABIS Grade 10 SABIS It is the measurement of reaction heats

The mechanism of a reaction cannot be deduced from net equation of the reaction. Grade 10 SABIS

2 carry out calculations using cycles and relevant energy terms, including: (a) determining enthalpy changes that cannot be found by direct experime A Level Chemistry CIE Applying Hess's Law is a powerful method in thermochemistry that allows us to calculate the overall enthalpy change of a reaction using known enthalpy changes of other reactions. This principle is based on the concept that enthalpy is a state function, meaning it depends only on the initial and final states of a system and not on the path taken. To construct a simple energy cycle using Hess's Law, we start with a target reaction for which we want to determine the enthalpy change. This target reaction may not have direct experimental data, but we can use known enthalpy changes of other reactions to derive the desired enthalpy change. The key idea is to break down the target reaction into a series of intermediate reactions, known as the "thermochemical equations," for which we have the corresponding enthalpy changes. By carefully selecting and manipulating these equations, we can cancel out common reactants and products to obtain the desired target reaction. For example, suppose we want to determine the enthalpy change for the combustion of methane (CH4). However, we don't have direct experimental data for this specific reaction. We can construct an energy cycle using known enthalpy changes of reactions involving the combustion of other compounds, such as hydrogen (H2) and carbon monoxide (CO). First, we identify the known reactions that can be used to build the energy cycle. In this case, we can use the combustion reactions of H2 and CO, for which we have the corresponding enthalpy changes. These reactions become the intermediate steps in the energy cycle. Next, we manipulate the intermediate reactions and their enthalpy changes to cancel out common species and align the stoichiometry with the target reaction. This can involve reversing reactions, multiplying them by coefficients, or combining multiple reactions to achieve the desired cancellation. By summing up the enthalpy changes of the manipulated intermediate reactions, taking into account the stoichiometric coefficients, we obtain the overall enthalpy change for the target reaction. This value represents the enthalpy change that would be measured if the reaction were directly carried out under standard conditions. It's important to note that the validity of applying Hess's Law relies on the assumption that enthalpy changes are additive. This assumption holds as long as the reactions occur under the same conditions and there is no change in temperature or pressure during the process. By applying Hess's Law and constructing simple energy cycles, we can determine the enthalpy changes of reactions that are difficult or impractical to measure directly. This approach provides a powerful tool for calculating enthalpy changes and understanding the energy transformations in chemical reactions. In summary, applying Hess's Law involves constructing energy cycles using known enthalpy changes of intermediate reactions to determine the enthalpy change of a target reaction. By manipulating and combining these reactions, we can cancel out common species and obtain the desired enthalpy change. This method allows us to calculate enthalpy changes for reactions that lack direct experimental data and enhances our understanding of energy transformations in chemical systems.

< Back Atomic Structure Lesson 3 ⚛️ Lesson 3 ⚛️ This section explores the subatomic structure of atoms and ions, highlighting the role of protons as unchanging identifiers of elements and the flexible nature of electrons in forming ions. The calculation of protons, neutrons, and electrons in an unknown element is demonstrated, unveiling the subatomic structure and identity of the element. Understanding these concepts allows us to uncover the hidden structure of the universe, atom by atom. Previous Next ⚛️ 1.1.3 Determining Subatomic Structure ⚛️ 💥🔬 Cracking the Code of Subatomic Structures: Protons, Electrons, and Neutrons 🔬💥 ⚛️ Atoms & Ions: A Tale of Charges ⚛️ Imagine an atom as a tiny city, bustling with life and balance. At its heart, it's neutral—like a well-managed city where everyone has a role to play. But sometimes, atoms get adventurous! They might lose or gain citizens (electrons), leading to charged cities we call ions. ⚡🌆 💫 Protons: The Unchanging Pillars of Atomic Identity 💫 The number of protons is like the DNA of an atom—it doesn't change and identifies the element. Be it the lithium city with 3 protons or the beryllium city with 4, every atom and ion of the same element shares the same proton number (atomic number). So, how do we count these unchanging pillars (protons) in an unknown element? With some simple math! 🧮📚 Mass number = number of protons + number of neutrons Number of protons = mass number - number of neutrons 💡 E.g., for an unknown element X with a mass number of 63 and 34 neutrons: Number of protons = 63 - 34 = 29 🎉 We just revealed the identity of element X—it's copper! 🥳🎉 💨 Electrons: The Flexible Players 💨 While protons are the steadfast pillars, electrons are more flexible—they may change in ions. In a neutral atom, the number of electrons equals the number of protons. But ions dance to a different tune: positively charged ions (cations) have fewer electrons, and negatively charged ions (anions) have more! 🎶🔄 For our mystery element X: Number of protons (and electrons in a neutral atom) = 29 🎯 ⚖️ Neutrons: The Balancing Act ⚖️ And finally, let's not forget the neutrons. They don't carry any charge but contribute to the mass. We can find their number with another bit of math: Number of neutrons = mass number - number of protons 🔍 E.g., for our element X with a mass number of 63 and 29 protons: Number of neutrons = 63 - 29 = 34 🎉 Just like that, we've unveiled the full subatomic structure of element X—Copper with 29 protons, 29 electrons, and 34 neutrons! 🔍🔬 By understanding these concepts, you're not just learning chemistry—you're uncovering the unseen structure of the universe, one atom at a time! 💥🌌 What can atoms become when they gain or lose electrons? A) Ions 🌟 B) Neutrons 🧪 C) Protons ⚡ D) Isotopes 🔬 The number of __________ determines the identity of an element. A) Electrons 💫 B) Protons ⚛️ C) Neutrons ⚡ D) Isotopes 🌌 How can we calculate the number of protons in an unknown element? A) Mass number + number of neutrons 🧮 B) Mass number - number of neutrons 📚 C) Number of neutrons + number of electrons 🌟 D) Number of electrons - number of neutrons 💡 What is the charge of a neutral atom? A) Positive ⚡ B) Negative 💥 C) Neutral 🔋 D) Variable 🌈 What happens to the number of electrons in ions? A) They remain the same as in neutral atoms. 🔁 B) They decrease in cations and increase in anions. ⬇️⬆️ C) They increase in cations and decrease in anions. ⬆️⬇️ D) They become neutral. ⚖️ In a neutral atom, the number of electrons is equal to the number of __________. A) Protons 🌟 B) Neutrons 🌌 C) Ions ⚛️ D) Isotopes 🔬 Which subatomic particles contribute to the mass of an atom? A) Protons and electrons 💥💫 B) Protons and neutrons 🧪⚛️ C) Electrons and neutrons ⚡🌌 D) Protons, electrons, and neutrons 🔬💥💫 How can we calculate the number of neutrons in an atom? A) Mass number - number of protons 🧮 B) Mass number + number of protons 📚 C) Number of protons - number of electrons 🔍 D) Number of protons + number of electrons 💡 Copper has an atomic number of 29. How many protons does a copper atom have? A) 29 🌟 B) 63 🔬 C) 34 🧪 D) 0 💥 An element has a mass number of 47 and 20 neutrons. How many protons does it have? A) 20 🌌 B) 27 ⚛️ C) 47 🧪 D) 67 🌟 Keep up the great work in unraveling the mysteries of subatomic structures and their impact on determining the identity of elements! Let your vibrant and creative knowledge shine brightly! 🌟🔬💫

Conservation of Mass Grade 10 SABIS SABIS In chemical reactions, the total mass of the reactants is equal to the total mass of the products. This principle states that matter cannot be created or destroyed.

Physical Change Grade 10 SABIS SABIS Produces no new kind of matter, is generally easily reversible, is not accompanied by great heat change, produces no observable change in mass

In general, reactions in which bonds are broken and formed tend to be slow. Grade 10 SABIS