The Structure of Atoms

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  • Topic: Atom, Neutron, Proton
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4Chapter 2: the Structure of the Atom
A) Matter 1. Matter 2 3 Element Compound 4. Atom 5. Molecule 6. Ion 7. Diffusion Is anything that occupies space and has mass. Is made up of tiny and discrete particles. There are spaces between these particles. These particles may be atoms, molecules or ions. Matter exists in three states  solid, liquid and gas Is a substance that consists of only one type of atom Is a substance that contains two or more elements that are chemically bonded together Molecule, Ion An atom is the smallest particle of an element that can participate in a chemical reaction. Metals and some non metals such as carbon and helium exist as atoms. Fe, Al, Mg, Au Is a group of two or more atoms which are chemically bonded together O2, H2 , H2O, CO2 Is a positively-charged or negatively-charged particle. Sodium Chloride, NaCl: Na+, ClOccur when particles of a substance, move in between the particles of another substance. Occur most rapidly in gases, slower in liquids and slowest in solids.

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The Kinetic Theory of Matter i. Solid a solid has a fixed volume and shape a solid cannot be compressed the particles are packed closely together in an orderly manner there are strong forces between the particles the particles can only vibrate and rotate about their fixed positions

ii. Liquid a liquid has fixed volume. It does not have a fixed shape but takes the shape of the container a liquid cannot be compressed easily The particles are packed closely together but not in orderly arrangement The particles are held together by strong forces but weaker that the forces in a solid The particles can vibrate, rotate and move through the liquid. They collide against each other

iii. Gas a gas does not gave a fixed shape or volume a gas can be compressed easily the particles are very far apart from each other and in a random motion there are weak forces between the particles ,the particles can vibrate, rotate and move freely. The rate of collision is greater that the rate of collision in a liquid © MHS 2009

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The change in the state of matter

Sublimation: Solid  Gas / Gas  Solid Melting : Solid  Liquid

Freezing: Liquid  Solid Evaporation or Boiling: Liquid  Gas Condensation: Gas  Liquid

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The kinetic theory of matter i. when a solid is heated, the particles in the solid gain kinetic energy and vibrate more vigorously the particles vibrate faster as the temperature increases until the energy they gained is able to overcome the forces that hold them at their fixed positions At this point, the solid becomes a liquid. This process is called melting. Melting point is the temperature at which a solid changes into a liquid at a particular pressure

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Example: Naphthalene C10H8

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The curve shows the changes in temperature when solid naphthalene melts

© MHS 2009

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At point A naphthalene exists as solid When the solid is heated, heat energy is absorbed. This cause the particles to gain kinetic energy and vibrate faster This is why the temperature increases from point A to point B

At point B solid naphthalene begins to melt during the melting process, the temperature 0Cof naphthalene does not rise, even though heating continues the temperature remains constant because the heat energy absorbed by the particles is used to overcome the forces between particles the solid can turn into liquid this constant temperature is the melting point of naphthalene at this temperature, both solid and liquid are present

At point C all the solid naphthalene has melted from point C to D, the particles in liquid naphthalene absorb heat energy and move faster the temperature increases from point C to point D

ii. When a liquid is cooled the particles in the liquid lose energy and move slower As the temperature continues to drop, the particles continue to lose more energy until they do not have enough energy to move freely At this point, the liquid changes into solid. This process is called...
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