State of Matter Chapter 4 - p Blue

Chap. 4 States of Matter Objectives 1) Understand the relation of atoms, molecules and matter. 2) Understand and know the difference between the three states of matter. 3) Understand the kinetic theory of matter. 4) Understand Pascal’s Principle. 5) Know and be able to explain certain vocabulary words. Chap. 4 – States of Matter - What does the state of matter tell you? Whether a material is solid, liquid, or gas IE – water Why are they solids, liquids, or gases? …you have to start with the particles that make up matter… - Matter: anything that takes up space and has mass… …anything that you can smell, taste or touch NOT matter…thoughts, emotions, light, heat… - What makes up matter? - Atom: smallest particle that makes up a given type of matter IE – atoms make up elements on the periodic table…gold only has gold atoms…

Two or more atoms combined = molecule –Atoms make up molecules… 1827 – Scottish Botanist – Robert Brown – noticed pollen grains moving constantly and randomly in water under a microscope… Today, scientists understand molecules move due to their continuous collisions with other molecules… –Brownian Motion…constant, random motion of tiny particles of ALL matter… This lead to…Kinetic Theory of Matter: idea that particles of ALL matter are in constant, random motion –Kinetic Energy: energy of moving particles

What does temperature do to matter? Higher temperature = molecules moving faster Lower temperature = molecules moving slower Do molecules ever stop moving? Only at absolute zero = C = temperature where particles cease to move… What happens when matter of higher temperature touches matter of a lower temperature? –energy is transferred from faster to slower particles –IE – walk outside on a cold day, faster molecules (your skin)…transfers energy to slower molecules (cold air) your brain tells you to go inside because you’re losing too much energy! –Heat is transferred energy from higher temperature matter to lower temperature matter… –What happens on a hot day? –(energy transferred from ? to ?…)

Matter in solid state… –IE – ice at …–250 C…molecules barely moving… –as temperature rises molecules move faster (shake more in all directions) but molecules stay in original position… –This is how Kinetic theory describes a solid = arrangement of shaking particles Two types of solids: 1) crystalline: particles are arranged in repeating geometric patterns 2) noncrystalline (amorphous): particles have no definite pattern or form Solid into a liquid –temp at which a substance changes from a solid to a liquid= melting point –IE – ice…as temp rises, molecules shake faster…still held in place by molecules around them until temp reaches 0 C…molecules break free from attractive forces, crystal structure collapses, solid becomes free flowing molecules in liquid state… –If not crystalline…glass…just get softer and softer as heat is added…begin to flow about 1000 C…above 2000 C…you can cut it with scissors…glass blowers continually turn it so it won’t drip off

Opposite of melting point, cooling a liquid… Attractive forces begin to trap particles and crystals form…= freezing point (same temp as a solid’s melting point) Liquid State particles move more freely than particles in a solid takes shape of the container fills container – if able gravity holds them on the bottom of container Forces Between Molecules How do insects stay on the top of water? Surface tension = attraction between water molecules IE – water beading up on a waxed car… Liquid Becoming a Gas IE – Heating up water… warm water rises, cool sinks, gets hotter, begins to bubble up (boil), water enters gaseous state… = Boiling Point = 100o C (for water) also called vaporization What about water that isn’t boiling? Temp. below 100o C – but it still disappears after awhile…

If you could watch molecules in a glass of water – some are moving fast…some are moving slow… Temp. is average kinetic energy of all molecules together… Fast molecules hit the surface of the water and break attractive forces Therefore, they escape into the air… = evaporation: process where individual particles of a liquid escape from the surface that is not boiling and form a gas For this to happen… –speed of molecules –near surface of water –heading in right direction (up) –avoid hitting other molecules

Cooling by evaporation: as fast molecules evaporate, molecules that remain are slower… Temperature: HOTTER = faster movement of molecules COOLER = slower movement of molecules Therefore…evaporation cools the liquid & anything it touches… IE – when sweat evaporates, it leaves us cooler IE - after a storm rain absorbs energy from everything around it…leaves the air cooler

Matter in Gas State molecules are much farther apart than in liquid & solid state a gas completely fills container it is in… bottle…room… as a gas cools, its particles slow down when they get slow enough, their attraction brings them together, which forms droplets of liquid = condensation Behavior of Gases & Liquids cooking bread in the kitchen… …where can you smell it in the house? warm molecules move faster…fills entire container…=…house! Ability to flow = liquids & gases are called fluids…

Gas particles are far apart, so they mix easily Mixing of particles = diffusion: when particles move from an area of high concentration to an area of low concentration IE – Some gases you can’t smell, but they are there…carbon monoxide…dangerous! Pressure: Amount of force applied per unit area Pressure = force/area Unit for pressure = pascal (Pa) Pascal’s Principle: pressure applied at any point to a confined fluid is transmitted throughout the fluid Squeeze container, fluid will find the exit IE – toothpaste, water bottle, mustard… IE – Your Heart… blood pressure…

Gas Pressure What causes gas pressure? = particles are constantly colliding with each other & the sides of the container IE – pump up tire/ball, you increase the number of particles in container… more particles, more collisions pressure limit on tires…? Atmospheric Pressure Particles in air collide with you… Ears popping at high altitudes…? - 17th century – French physician Blaine Pascal Measured pressure at different altitudes Experiment: carry balloon to the top of a mountain, balloon expanded as it got higher… Why? …Air is thinner…fewer particles >>> less pressure… Ears? …air gets trapped in ears…as you go higher…less pressure… Releases air in ears…POPS!

Float or sink? Density –D = M/V –Find mass, find volume –Then divide mass by volume. –Tells us what? Higher than 1 = sink Lower than 1 = float density of water = 1 –Density is used to identify objects Buoyancy: difference in pressure results in an upward force on an object immersed in a fluid If buoyant force is equal to the weight of the object, the object will float If buoyant force is less than the weight of the object, the object will sink decrease in weight caused by the buoyant force Archimedes’ Principle: the buoyant force of an object is equal to the weight of the fluid displaced by the object - Beaker filled with water, place object in beaker, water spills out. - weight the spilled water = buoyant force of object