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Questions and Answers
What occurs to gases at extremely low temperatures, close to absolute zero?
The Law of Conservation of Energy states that energy can be created or destroyed in a chemical reaction.
False
Who discovered the electron and in what year?
J J Thomson in 1897
The density of water is _______ g/mL.
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Match the following terms with their description:
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Which branch of chemistry focuses on the study of compounds containing carbon and hydrogen?
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Weight and mass are two terms that can be used interchangeably without any differences.
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What is the definition of a pure substance?
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The energy possessed by an object due to its motion is known as __________ energy.
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Match the following states of matter with their properties:
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Study Notes
Introduction to Matter
- Chemistry explores matter, its properties, changes it undergoes, and associated energy.
- Matter is defined as anything that occupies space and has mass.
Mass vs Weight
- Mass measures the quantity of matter within a sample.
- Weight is the gravitational force acting on an object's mass.
Branches of Chemistry
- Organic Chemistry: Focuses on carbon-based compounds.
- Inorganic Chemistry: Covers all other compounds, including some simpler carbon compounds.
- Analytical Chemistry: Involves the detection and quantification of substances.
- Physical Chemistry: Merges physics principles with chemical systems.
- Biochemistry: Addresses chemical processes in living organisms.
Energy
- Energy is the capacity to perform work and induce changes in matter, existing in forms like mechanical, light, heat, and electrical.
Kinetic and Potential Energy
- Kinetic Energy: Energy due to an object's motion.
- Potential Energy: Energy stored in an object due to its position or condition.
Energy Changes in Chemical Reactions
- Exothermic Reactions: Release energy to surroundings (e.g. combustion).
- Endothermic Reactions: Absorb energy from surroundings (e.g. melting ice).
Changes of Matter
- Chemical Change: Alters the chemical composition and identity of substances (indicated by color changes, gas evolution, precipitate formation, temperature variations).
- Physical Change: Changes only the appearance without altering composition (e.g. melting of ice).
Composition of Matter
- Pure Substance: Consistent composition and distinct qualities; cannot be decomposed physically.
- Mixture: Combination of substances that retain identities, can be separated physically.
Properties of Matter
- Chemical Properties: Describe how substances react to form other substances (e.g. flammability, susceptibility to corrosion).
- Physical Properties: Observable without chemical alteration; characteristics include color, density, and melting point.
- Extensive Properties: Depend on the amount of material (e.g. mass, volume).
- Intensive Properties: Independent of material amount; includes color and density.
Classification of Matter
- Homogeneous Mixture: Uniform composition throughout (e.g. solutions).
- Heterogeneous Mixture: Non-uniform composition with distinguishable properties (e.g. oil and water).
States of Matter
- Solid: Definite shape, rigid structure; slightly compressible.
- Liquid: Defined volume, takes shape of its container; flows easily.
- Gas: No fixed volume or shape, highly compressible and expandable.
- Plasma: Ionized gas at high temperatures, consists of charged particles.
- Bose-Einstein Condensate: Occurs at temperatures near absolute zero, leading particles to condense.
Measurements of Matter
- Uses International System of Units (SI Units) for standardization.
- Mass measured in kilograms, length in meters, and temperature in Kelvin.
- Density is calculated as mass per unit volume (g/cm³ or g/mL).
Natural Laws
- Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.
Discovery of Atomic Structure
- J.J. Thomson discovered the electron in 1897 through cathode ray tube experiments, revealing its charge-to-mass ratio.### Atomic Theory of Matter
- Robert Millikan determined the electron’s charge as ( -1.602 \times 10^{-19} ) C through the oil-drop experiment.
- The electron mass is approximately ( 9.11 \times 10^{-31} ) g.
Law of Conservation of Mass
- Proposed by Antoine Lavoisier; states that matter is conserved in chemical reactions.
- The total mass of reactants equals the total mass of products.
- J.J. Thomson's charge-to-mass ratio supported this law.
Law of Conservation of Matter and Energy
- Asserts that the total amount of matter and energy in the universe remains constant.
Law of Definite Proportion/Composition
- Joseph Louis Proust found that pure compounds always have consistent compositions by mass.
- Example: 100 g of calcium carbonate (CaCO3) contains consistent ratios of elements.
Law of Multiple Proportions
- John Dalton expressed that if two elements form more than one compound, the masses of one element, when combined with a fixed mass of the other, are in small whole number ratios.
John Dalton's Contributions
- Referred to as the father of modern atomic theory; published ideas in 1808 based on experimental data.
- Proposed foundational atomic principles:
- Atoms are indivisible and fundamental.
- All atoms of an element have identical properties but differ from other elements.
- Atoms cannot be created or destroyed in reactions.
- Compounds form in simple whole-number ratios.
Drawbacks of Dalton's Atomic Theory
- Atoms are divisible into subatomic particles (protons, electrons, neutrons).
- Presence of isotopes means atoms of the same element can have different masses.
- Complex organic compounds do not always follow simple whole-number ratios.
- Existence of allotropes challenges the notion that atoms of different elements have completely distinct properties.
Nuclear Model of the Atom
- Proposed by Ernest Rutherford with Hans Geiger through gold foil experiments, leading to the identification of the nucleus.
- Nucleus contains protons and neutrons; electrons orbit at a distance.
Ions and Net Charge
- Ions are atoms that have gained or lost electrons, resulting in net charges:
- Anions: negatively charged (gain of electrons).
- Cations: positively charged (loss of electrons).
Atomic Number and Mass Number
- Atomic number equals the number of protons in an atom.
- Mass number is the total of protons and neutrons.
Isotopes
- Frederick Soddy introduced "isotopes" for atoms of the same element with different masses due to varying neutron numbers.
- Example: Uranium-235 and Uranium-238, both with 92 protons but different neutron counts.
Atomic Mass
- Atomic mass (or atomic weight) is the weighted average of isotopic masses based on relative abundance.
- Conversion factor: 1 amu is approximately ( 1.66054 \times 10^{-24} ) g.
Discoveries in Radioactivity
- Henri Becquerel discovered that uranium compounds emit high-energy radiation.
- Marie and Pierre Curie explored the radioactivity of uranium, leading to isolation of radioactive sources.
- Gamma rays, alpha particles, and beta particles were identified, expanding nuclear physics.
- James Chadwick discovered neutrons, leading to a deeper understanding of atomic structure.
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Description
This quiz explores the fundamentals of matter, including its properties, composition, and the various changes it undergoes. It delves into the principles of chemistry and how matter interacts with energy. Perfect for students seeking to solidify their understanding of these key concepts.
