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Energy and States of Matter Unit 1 Physical Science HS Credit Mrs. Rubel The States of Matter • States of matter are the physical forms in which a substance can exist: Solid (crystalline and amorphous) Liquids (with surface tension and viscosity) Gas (pressure, Boyle’s Law and Charles's Law) Plasma (conductivity) Solids • When matter has a definite shape and volume. The particles are so close together that the atoms or molecules move, but not fast enough to overcome the gravitational attraction between them. Each particle is locked into place by the particles around it. 2 Types of Solids • Crystalline solids – atoms/molecules are arranged in repeating pattern of rows. Ex: diamonds, ice and iron. • Amorphous solids –atoms/molecules are not in a particular order or organized pattern. Ex: wax, rubber. Liquids • Liquids take the shape of the container they are in. The atoms can move fast enough to overcome the attraction between them. The volume remains the same, regardless of the container. Buoyancy • The ability of a fluid to exert an upward force on an object immersed in it. • If the buoyant force is equal to the object’s weight, then the object will float. • If the buoyant force is less than the object’s weight, then the object will sink. Archimedes’ Principle • Archimedes and the Volume of Gold • Object will sink until the weight of the water displaced equals the weight of the object. How does a steel ship float? • Bottom portion of the ship will sink until the weight of the ship and the buoyancy of the water are balanced. This is possible because of the compartments of air. • Titanic vs. iceberg (guess who wins?) Pascal and Hydraulics Pressure = force per unit area F P A Pascal’s Principle states that pressure applied to a fluid is transmitted throughout the fluid (ex: hydraulics) • Hydraulics: when liquids in a container are pressed, the liquids move outward, causing pressure. This pressure can be a force that can do work. Examples: dentist chair, car brakes. Bernoulli’s Principle Bernoulli realized that, as the velocity of a fluid increases, the pressure exerted by the fluid decreases. Examples: chemical sprayers (see page 488), airplane wings Liquid Properties • Surface tension – the force that acts upon the particles at the surface of a liquid, causing the liquid to form spherical drops. Viscosity – A liquid’s resistance to flow. The stronger the attraction between a liquid’s particles, the more viscous the liquid is. Example: Honey and motor oil (yum!) LCDs • Liquid Crystals have characteristics of both solids and liquids. They will begin to melt at melting point, but they do not lose their arrangements – they retain their geometric order in specific directions. • Because they respond to electromagnetic fields, they can be used in the displays of watches, calculators, etc. Gases • Gas – the matter can change both shape and volume. The atoms/molecules move so fast they can break away from the attraction from each other. As gases expand, there is actually empty space between particles. • Pressure – The amount of force exerted on a given area. The more gas you have in a given area, the more the crowded particles collide with each other at a faster rate. Gases Fill Their Containers • When the attractive forces between particles is overcome, then the movement/collision between particles will cause diffusion. Diffusion is the spreading of particles throughout a given volume until they are uniformly distributed. Diffusion can occur in solids and liquids, but most rapidly in gases. Gas Laws (think pressure and volume) • Boyle’s Law – For a fixed amount of gas at a constant temperature, the volume of this gas increases as it’s pressure decreases. Example: Balloons. If you squeeze a balloon, you are applying pressure to the gas inside. The particles of gas are forced to move close together. If you let go and release pressure, than the gas expands in volume. How Boyle’s Law Works Boyle’s Law and Weather Balloons • When meteorologists release weather balloons, they only put a small volume of gas in each balloon. The balloon will travel to the upper layers of our atmosphere to get the information, where the air is thin. • Partner share: How does this apply to Boyle’s Law? Boyle’s Law • A balloon has a volume of 8.0 L at a pressure of 90 kPa. What will be the new volume is the pressure drops to 40.0 kPa? Boyle’s Formula = P1V1 = P2V2 • P1 = 90.0 kPA V1 = 8.0 • P2 = 40.0 kPA V2 = ? So… P1V1 (90.0 kPa) (8.0 L) • V2 = P2 V2 = 40.0 kPa = 18 L Charles Law (think temperature and volume) • For a fixed amount of gas at a constant pressure, the volume of the gas increases as its temperature increases. The volume of gas will decrease as the temperature decreases. Why? When the temperature increases, the particles of gas move faster and expand as much as they can (increase volume). If it is cooler, the particles slow down and do not expand (decrease volume). Charles’s Law Using Charles’ Law V1 V2 T1 = T2 (Pressure must remain constant) A 3.0 L balloon at 10.0oC was placed in a container of ice water (2.0oC). What is the resulting volume? V1 = 3.0L T1 = 10 0oC V2 = ? T2 = 2.0oC Charles’ Law • Absolute Zero - Temp at which... – the volume of a gas would equal zero. – all particle motion would stop. -273°C or 0K Last State of Matter: Plasma • Plasma doesn’t have a definite shape or volume, and the particles have broken apart. • However, plasma has conductivity, which means that an electric current can go through it. Electric and magnetic fields can affect plasmas, but not gases. • Natural plasmas are found in lightning, fire and in the aurora borealis (Northern Lights). • The artificial plasmas created in fluorescent lights are created by passing electrical currents through the gasses. Artificial and Natural Plasma Changes of State • All changes of state are physical changes. • The change requires a change in energy. If energy is removed, then the particles move slower (water to ice). If energy is added, then the particles move faster (raising the temperature). • Heat, which is a transfer of energy, causes temperature changes, which causes a change in state. The 4 Changes of State 1)Melting Solids to Liquids – the melting point is the temperature when a solid becomes a liquid. Melting point is a characteristic property of a substance. • Melting is an endothermic change, because energy is absorbed by the substance as it changes state. This energy increases the motion of the molecules until they can overcome their attractions to each other. The 4 Changes of State (continued) 2) Freezing Liquids to Solids- This is at the substance’s freezing point. Remember, you don’t loose energy (it changes form) Proof that freezing and melting points are the same…… Heating Curve of a Liquid When thermal energy (heat) is added, the liquid begins to change state. The freezing/melting points are equal, as are the points for boiling/vaporization. At 0oC, all energy is put into the ice to overcome attractive forces of particles. At 100oC, the water is using all energy for boiling or vaporization. See the graph on page 480. Ice Water: The energy added to 0oC will melt the ice, but it was removed at the same temperature to freeze the water! So why doesn’t the water freeze? The 4 Changes of State (continued) 3) Vaporization: Liquids to Gases - boiling is vaporization that occurs when a substance reaches its boiling point, which then leads to evaporation. - Evaporation – vaporization that occurs at the surface of a liquid below it’s boiling point. The particles at the surface move fast enough to break away from the surrounding particles, and thus become a gas. Thermal Expansion • Thermal expansion is an increase in the size of a substance when the temperature is increased. • When the temperature of an object is lowered, particles slow down. The attraction between the particles increases, so they move closer together. Thermal Expansion and Density • When heat is added and particles begin to expand, then there is a increased distance between the particles. This expansion means a decrease in density. • This is why air is heated in a hot air balloon. The air inside the balloon is less dense than the outside air, so the balloon will rise. Boiling Point and Pressure • Question: • You visit a friend in Denver, Colorado. You are cooking pasta, and you notice that it takes very little time for the water to boil. It appears to boil much faster than it did in Atlanta. There must be some relationship between the higher altitude and the boiling point of water. What is it? The 4 Changes of State (continued) 4) Condensation – Gases to Liquids The condensation point of a substance is the temperature at which the gas becomes a liquid and the same temperature as the boiling point at a given pressure. Example: at sea level the same temperature that causes evaporation creates steam (condensation). The energy is removed (exothermic change) so that the molecules of the evaporated gas cool enough to slow down and clump together. The “5th State” Sublimation Sublimation - when solids go directly into a gas. This can only occur when the atoms or molecules must move from being very tightly packed to being very spread apart (completely overcoming the attraction). This also requires energy (endothermic change). Example: dry ice. Once heat energy is added, it goes from a solid to a gas.
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