Quantification_of_Elements_and_Compounds_-_____(Science_Grade_10_Lesson_7)-2.pdf

📖 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) Tags Relative Atomic Mass (Ar) What is Relative Atomic Mass? (සාපේක්ශ පරමාණුක ස්කන්ධය) R...

📖 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) Tags Relative Atomic Mass (Ar) What is Relative Atomic Mass? (සාපේක්ශ පරමාණුක ස්කන්ධය) Relative atomic mass is a way to express how heavy different atoms are compared to a chosen standard atom. Key Points Explained Simply 1. Standard Atom: In the past, scientists used the mass of a hydrogen atom (the lightest element) as the basic unit to compare other atoms. This means that the mass of hydrogen was set as a reference point. Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 1  2. Comparison: Instead of saying how much an atom weighs in grams (which would be a very small number), scientists compare the weights of other atoms to this standard. For example, if an oxygen atom is heavier than hydrogen, its relative atomic mass would be a number greater than 1. 3. Not True Mass: The relative atomic mass does not represent the actual mass of an atom in grams. Instead, it tells us how the mass of one atom compares to the mass of the hydrogen atom. 4. Current Standard: Today, the carbon-12 atom is often used as the standard for relative atomic mass, with its mass set to exactly 12. This change was made to improve accuracy in measurements. Summary In simple terms, relative atomic mass is a way to compare the weights of different atoms using a standard reference atom (like hydrogen or carbon-12). It helps scientists understand how heavy atoms are relative to each other without dealing with tiny numbers. Atomic Mass Unit What is an Atomic Mass Unit (AMU)? An atomic mass unit (AMU), also known as a dalton (Da), is a unit of mass used to express the masses of atoms, molecules, and subatomic particles. It is defined as exactly 1/12 the mass of a carbon-12 atom. Key Points Definition: 1 AMU is defined as exactly 1/12 the mass of a carbon-12 atom at rest in its ground state. Conversion to grams: 1 AMU is equal to approximately 1.66 × 10^-24 grams. Relationship to protons and neutrons: Each proton and neutron in an atom has a mass of approximately 1 AMU. Interchangeable with dalton: AMU and dalton (Da) are used interchangeably and are defined the same way. Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 2  Examples Mass of a hydrogen-1 atom: 1.007 AMU Mass of a helium-4 atom: 4.0026 AMU Mass of a sulfur-32 atom: 31.972 AMU In summary, the atomic mass unit is a convenient way to express the masses of atoms and molecules on the atomic scale, with 1 AMU being defined as exactly 1/12 the mass of a carbon-12 atom. Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 3 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 4  Relative Molecular Mass Relative molecular mass (Mr), also known as molecular weight, is the weighted average mass of a molecule compared to one-twelfth of the mass of a carbon-12 atom. It is calculated by summing the relative atomic masses of all the atoms in a molecule. Key Points Definition: Relative molecular mass is the total of the relative atomic masses of the atoms in a molecule, expressed as a ratio to one-twelfth of the mass of a carbon-12 atom. Calculation: To find the relative molecular mass of a compound, you simply add the relative atomic masses of its constituent elements, multiplied by the number of times each element appears in the molecule. Example Calculation For example, to calculate the relative molecular mass of sulfuric acid (H₂SO₄): 1. Identify the elements and their relative atomic masses: Hydrogen (H): 1 Sulfur (S): 32 Oxygen (O): 16 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 5  2. Determine the number of each atom in the molecule: H₂SO₄ has: 2 hydrogen atoms 1 sulfur atom 4 oxygen atoms 3. Calculate the relative molecular mass: 💡 Mr(H₂SO₄) = (2 × Ar(H)) + (1 × Ar(S)) + (4 × Ar(O)) = (2 × 1) + (1 × 32) + (4 × 16) = 2 + 32 + 64 = 98 Conclusion The relative molecular mass of sulfuric acid (H₂SO₄) is 98. This value is dimensionless and provides a comparative measure of the mass of the molecule relative to the carbon-12 standard. Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 6  Avogadro Constant Avogadro's Constant 💡 Definition: Avogadro's constant is the number of atoms or molecules in one mole of a substance, which is approximately 6.022 × 10²³. Key Points 1. For Elements: When you take a mass of an element equal to its relative atomic mass in grams, it contains 6.022 × 10²³ atoms. For example: Carbon (C): 12 g has 6.022 × 10²³ atoms. Hydrogen (H): 1 g has 6.022 × 10²³ atoms. Chlorine (Cl): 35.5 g has 6.022 × 10²³ atoms. 2. For Compounds: When you take a mass of a compound equal to its relative molecular mass in grams, it contains 6.022 × 10²³ molecules. For example: Water (H₂O): 18 g has 6.022 × 10²³ molecules. Carbon Dioxide (CO₂): 44 g has 6.022 × 10²³ molecules. Glucose (C₆H₁₂O₆): 180 g has 6.022 × 10²³ molecules. Conclusion Avogadro's constant helps us understand how many atoms or molecules are in a given amount of a substance, making it a fundamental concept in chemistry. Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 7  Mole A mole is a unit used in chemistry to measure the amount of a substance. It's like using a dozen to measure eggs - just like a dozen always has 12 eggs, a mole always has 6.022 × 10²³ particles (atoms, molecules, or ions). Some key points about the mole: 1. Definition: One mole is equal to 6.022 × 10²³ particles. This number is called Avogadro's number. 2. Particles: The particles can be atoms, molecules, ions, or any other tiny thing in chemistry. 3. Relationship to mass: One mole of a substance has a mass equal to its molar mass. For example, one mole of carbon-12 atoms has a mass of exactly 12 grams. 4. Counting particles: The mole helps us count the number of particles in a substance. For instance, if you have 3 moles of water (H₂O), you have 3 × 6.022 × 10²³ = 1.81 × 10²⁴ water molecules. 5. Balancing chemical reactions: Moles are used to balance chemical equations. For example, in the reaction 2H₂ + O₂ → 2H₂O, the coefficients represent the molar ratios of the substances. In simple terms, a mole is just a way to count particles in chemistry, similar to how a dozen is used to count eggs. It's a very large number (6.022 × 10²³), but it helps us understand the amounts of substances involved in chemical processes. Molar Mass Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is calculated by adding together the atomic masses of all the atoms in a molecule or formula unit of that substance. Key Points 1. Definition: Molar mass (M) is the mass of a chemical compound divided by the amount of substance measured in moles. It tells you how much one mole of that substance weighs. Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 8  2. Units: The standard unit for molar mass is grams per mole (g/mol), but it can also be expressed in kilograms per mole (kg/mol). 3. Calculation: To calculate the molar mass: Identify the elements in the compound and their respective atomic masses (found on the periodic table). Multiply each element's atomic mass by the number of times it appears in the formula. Sum these values to get the total molar mass. For example, for water (H₂O): 💡 Hydrogen (H) has an atomic mass of about 1 g/mol, and there are 2 hydrogen atoms: 2 X 1 = 2g/mol 💡 Oxygen (O) has an atomic mass of about 16 g/mol: 1 X 16 = 16 g/mol. 💡 Total molar mass of water = 2 + 16 = 18g/mol 4. Importance: Molar mass is essential for converting between the mass of a substance and the number of moles, which is important in chemical reactions and stoichiometry. In summary, molar mass is a crucial concept in chemistry that helps quantify the mass of substances in relation to the amount present, facilitating calculations in chemical reactions. Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 9 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 10 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 11 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 12 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 13 Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 14  Summery Quantification of Elements and Compounds - මූලද්‍රව්ය හා සංයෝග ප්‍රමාණනය (Science Grade 10 Lesson 7) 15