Phase Changes in Matter PDF

# Phase Changes in Matter ## Evaporation Evaporation is the process by which liquid turns into gas. This happens when molecules at the surface of the liquid gain enough energy (usually from heat). ## Melting Melting is the process of a solid turning into liquid when heated, as its particles gain...

# Phase Changes in Matter ## Evaporation Evaporation is the process by which liquid turns into gas. This happens when molecules at the surface of the liquid gain enough energy (usually from heat). ## Melting Melting is the process of a solid turning into liquid when heated, as its particles gain energy and move more freely. ## Condensation The process where a gas turns into a liquid. As the gas cools the molecules lose energy, slow down and come closer together, forming a liquid. ## Heating Is the process of adding heat energy to a substance causing its particles to move faster and potentially leading to phase changes like melting or evaporation. ## Cooling Cooling is the process of removing heat from a substance which causes its particles to slow down. As a result, a substance may undergo phase changes such as freezing (liquid to solid) or condensation (gas to liquid). # 3 Sub-atomic Particles of an Atom ## Proton A proton is a sub-atomic particle with a positive electric charge that is found in the nucleus of an atom. - Symbol: p+ indicates that the proton carries a positive charge. - Charge: +1.6 x 10^-19 - Actual Mass: 1.6726 x 10^-27 kilograms - Location: Proton is located in the nucleus of an atom - Actual mass: Very small compared to protons and neutrons, approximately 9.109 x 10^-31 kg. ## Neutron A neutron is a subatomic particle that is one of the fundamental parts of an atom. - Nucleus: Central part of an atom. - Symbol: n or n° - Indicates that it has no electric charge (NEUTRAL) ## Electron An Electron is a fundamental subatomic particle that plays a crucial role in the structure of atoms and the behavior of matter. - Atom: Smallest particle of an element. - Symbol: e- - 2: Denotes the particle itself. - -: Indicates its negative charge. - Charge: Negative charge (-1.6024 x 10^-19 coulombs). ### Atomic Model #### Early Philosophical Concepts First Greek philosophers, notably Leucippus and Democritus, proposed the concept of the atom, they envisioned atoms as tiny, solid, indestructible particles of different shapes and sizes, forming the basis of all matter. However, this was purely philosophical speculation lacking experimental evidence. #### Dalton's Atomic Theory (Early 1800s) John Dalton's atomic theory marked a significant shift towards a scientific understanding. Based on experimental observations of chemical reactions, Dalton proposed: - All matter consists of invisible atoms. - Atoms of the same element are identical in mass and properties. - Atoms of different elements have different masses and properties. - Atoms combine to form molecules in simple whole-number ratios. #### Thomson's Plum Pudding Model (1899) Thomson proposed the plum pudding model, challenging Dalton's model. Thomson proposed a plum pudding model where atoms are positively charged spheres with negatively charged electrons embedded within it. #### Rutherford's Nuclear Model (1911) Ernest Rutherford's gold foil experiment revolutionized atomic theory. By bombarding a thin gold foil with alpha particles, he observed that most passed straight through while a few were deflected at a large angle. This led to the nuclear model: - Atoms are mostly empty space. - a small dense positively charged nucleus resides at the atom's center. - Negatively charged electrons orbit the nucleus. #### Bohr's Model (1913) Niels Bohr addressed the stability issue by proposing that electrons orbit the nucleus in specific energy levels or shells. Electrons can only exist in these quantized orbits, and transitions between orbits involve the absorption or emission of energy. This successfully explained the hydrogen atom's spectrum but failed to accurately predict the spectra of more complex atoms. #### The Quantum Mechanical Model (1920s) - The quantum mechanical model developed by Schrodinger, Heisenberg, and others is the current accepted model. # Periodic Table - Trace the development of the periodic table from earlier versions based on similarities and properties of elements.