Solids, Liquids, and Gases

Kinetic Theory The kinetic theory is an explanation of how particles in matter behave. All matter is composed of small particles (atoms, molecules, ions) These particles are in constant, random motion. These particles are colliding with each other and the walls of their container.

Cool Science http://youtu.be/bPh1KXA8egU

Thermal Energy All objects have energy Potential Energy – from the bonds that hold the substance together Kinetic Energy – from the motion or vibration of the atoms and molecules The total energy of a material’s particles is called the thermal energy.

Thermal Energy More energy = more motion = higher temperature

Temperature Temperature measures the average kinetic energy of the particles in a substance.

Solids Particles are closely packed together Particles have different geometric arrangements. These arrangements determine the physical and chemical properties.

Carbon

Liquids Particles have enough energy to break free from the geometric arrangement. Substance flows and takes the shape of its container. Melting point – temperature at which a substance goes from solid to liquid Heat of Fusion – energy required to reach the melting point

Gases Particles have enough energy to escape the attractive force of the other molecules. Expand to take the size and shape of their container Heat of Vaporization – amount of energy required for a liquid to become a gas Diffusion – spreading out of gas molecules to fill their container.

Boiling Boiling point – temperature at which a substance goes from a liquid to a gas. Liquids stay in their container because of air pressure. Liquids boil because the internal pressure of the liquid becomes equal to the pressure of the air and the molecules are allowed to escape.

Heating Curves Graph that shows the states of matter of a substance. As a solid melts and a liquid vaporizes the temperature remains constant. The temperature increases after the phase change has happened.

Heating Curves

Plasmas High temperature gas with positively and negatively charged particles. Found in lightning and neon signs

Thermal Expansion Increase in the size of a substance when it is heated. Occurs in most solids, liquids, and gases. Water is the exception.

Weird Things Some substances do not react as expected when changing states. Amorphous Solids Lack the geometric pattern of other solids Glass and Plastic No definite melting/boiling point Liquid Crystals Keep their geometric arrangement when liquid Liquid Crystal Displays Non-Newtonian Substances Acts as different states based on certain conditions

Buoyancy The ability of a fluid (liquid or gas) to exert an upward force on an object immersed in it. If the buoyant force is equal to the weight of the object, the object will float. If the buoyant force is less than the weight of the object, the object will sink.

Archimedes’ Principle The buoyant force on an object is equal to the weight of the water displaced.

Density Mass ÷ Volume More dense objects sink Less dense objects float To increase the density you can: Decrease the volume Increase the mass To decrease the density you can: Increase the volume Decrease the mass

Pressure Pressure = Force / Area To increase the pressure: Increase the force Decrease the area To decrease the pressure: Decrease the force Increase the area

Pascal’s Principle Pressure is constant throughout a fluid In simple terms, pressure is the same in a fluid. Force 1 / Area 1 = Force 2 / Area 2 Hydraulic Lifts

Bernoulli’s Principle As the velocity of a fluid increases, the pressure decreases. Fast air = less pressure Slow air = more pressure Airplane wings are designed so that the air moves faster on the top. That means there is a small pressure pushing down and a bigger pressure pushing up. The airplane is then able to fly.

Viscosity The resistance of a fluid to flow Low viscosity = flows easily (water, milk) High viscosity = does not flow easily (syrup, ketchup)

Assignment Section 2 Reinforcement On the back, answer these questions: What are two opposing forces that act on an object floating in water? Why do helium balloons float and non helium balloons sink? Why are roofs lifted off houses during tornados? How is it possible for a heavy boat to float on water?