Kinetic Theory of Matter Matter is made up of particles which are in continual random motion Misconception: Only when a substance is in its liquid or gas state do its particles move because in these two states the substance is fluid (it flows). Truth: in order for the molecules of any substance to stop moving completely, the substance would have to be frozen to absolute zero, a temperature unattainable in nature.
The Four States of Matter Solid Liquid Gas Plasma
Particles of solids are tightly packed, vibrating about a fixed position. Solids have a definite shape and a definite volume. Sometimes the arrangement of particles is regular and geometric and crystals are formed and sometimes the material is amorphous.
Which one is more dense? Which ones in each set below have more population density and why? Set A Set B The one on the right has more density. MORE people, same space. They both have the same density. MORE people in the second one but MORE space as well
Which one is more dense Item A or Item B - and why? Ans. Item B is more dense. It occupies LESS space but has the SAME mass as Item A. That s why the scale is balanced. Item A Item B
Which Which one one is is more more dense dense and and why? why? Ans. Here we can t tell. Item A has MORE mass, but also occupies MORE space. Item B Item A
What is density? The density of a substance is the mass per unit volume it has, in other words, how compact the substance is. The formula for density is: density m ass units _gm_ cm 3 volum e
Elasticity Some objects stretch and return to their original shape. These objects are elastic. Objects that don t return to their original shape are inelastic. The amount of stretch (x) of an elastic object is directly proportional to the force (F) that stretches it. This is called Hooke s Law: 2 cm 10 kg 20 kg 4 cm 8 cm F x Elastic Inelastic 40 kg
Elasticity Example A certain spring stretches 45 cm when a weight of 100 N is suspended from it. How much will it stretch if a force of 20 N is suspended from it? 100 N 45 cm 20 N? cm F x F1 x 1 100N 45 cm F x 2 2 20N x 2 100x 2 20Nx 45cm 100x 2 900 x 2 9 cm
Scaling The SURFACE AREA and VOLUME of a cube (2 units on a side) are shown: 2 units long x 2 units wide x 6 sides S. Area: 24 un 2 2 units long 2 units wide x 2 units deep Volume: 8 un 3 Suppose we double the linear dimensions (length, width, and height). What happens to the SURFACE AREA and the VOLUME of our cube? 4 units long x 4 units wide x 6 sides S. Area: 96 un 2 4 units long 4 units wide x 4 units deep Volume: 64 un 3 DOUBLING (x2) the linear dimensions results in QUADRUPLING (x4) the surface area and OCTUPLING (x8) the volume
Densities of some common materials Density Density Material (in gm/cm 3 ) Material (in gm/cm 3 ) Osmium 22.6 Steel 7.8 Gold 19.3 Ice 0.92 Lead 11.3 Water at 4 C 1.00 5 cm Find the mass of the following objects: 2.5 cm 3 cm Gold 5 cm Ice Lead Volume = l x w x h Volume = r 2 h Volume = 4/3 r 3
Liquids have an indefinite shape and a definite volume. Particles of liquids are tightly packed, but are far enough apart to slide over one another.
Liquid Layers Which layer has the highest density? Which layer has the lowest density? Which is fresh water, oil, salt water, alcohol?
Where is the pressure greater? 5 m 10 m EVIDENCE: If one were to make a hole in the side of each container, the water would squirt out much further out of the bottom one
The volume of the water displaced equals the volume of the irregularly shaped object. How do you find the volume of an irregularly (non-geometrically) shaped object?
Where does bouyancy come from? In other words, why do objects feel lighter underwater? There is a pressure difference between the top and the bottom of the object which are at different depths. Bouyant Force
An object will float when F w the Bouyant Force is greater than the weight of the object
An object will float when F w the Bouyant Force is greater than the weight of the object
An object will float when F w the Bouyant Force is greater than the weight of the object
0 N 5 3 Archimedes Principle An immersed object is buoyed up by a force equal to the weight of the fluid it displaces Apparent weight of rock Weight of water displaced Total Weight of Object in air 3 N + 2 N = 5 N 0.0 2.0 N
Pascal s Principle Changes in pressure at any point in an enclosed fluid at rest are transmitted undiminished to all points in the fluid and act in all directions (because fluids are uncompressible)
Pascal s Principle If the pistons have different areas, then the pressure (force per unit area) will be the same. This allows heavy loads to be lifted (LARGE FORCE). However, they will be lifted over a small distance. d d
Principle of Flotation A floating object displaces a weight of fluid equal to its own weight. 0 N 0 N 5 N 5 N The trick to get something more dense than water to float is to shape it so that it displaces as much water as its own weight.
REMEMBER: the bouyant force is determined by the volume of water displaced, not by the weight of the object. That s why the same one ton piece of iron (see below) sinks when shaped like a block but floats when molded into a bowl shape F B F B F w F w
A 1-kg rock weighs 9.8 N. The water in the container below also weighs 9.8 N. When submerged underwater, the rock s apparent weight is 7.8 N. A. What is the bouyant force on the rock? B. If the container of water on the 7.8 N scale weighs 9.8 N, what is the scale reading when the rock is suspended beneath the surface of the water? C. What is the scale 0 N 0 N 0 N reading when the rock is resting on? N? N the bottom of the 9.8 N container? 9.8 N
Gases have an indefinite shape and an indefinite volume. Particles of gases are very far apart and move freely.
Both liquids and gases are fluids, and basically obey the same principles, but there are some differences... Ocean of Air Ocean of Water pressure with incr. depth. density at bottom. Temperature with incr. depth. pressure with incr. depth. Same density throughout. Temperature with incr. depth.
At sea level, one cubic meter of air at 20 C, has a mass of about 1.2 kg. 1 m 3 of air 1.2 kg
The weight of air upon one-square meter of ground at sea level is about 100,000 N (10,200 kg). So atmospheric pressure is about: 100,000 Newtons per square meter or 100,000 N/m 2 or 100,000 Pascals or 100 kpa
In order to keep the cabin pressurized at all altitudes, a commercial airliner like a 747 carries up to 1000 kg of additional air in tanks.
Air pressure pushing on well water Vacuum created here WATER PUMP. When you push down the crank, it sucks the air out of the chamber with a piston allowing air pressure to push down on the water in a well through one tube and making it rise to the surface through the other tube. Water rising to the surface
The varying pressure of the air on a dish of mercury can produce a measuring device called a barometer. 76 cm Normal Atmospheric Pressure Lower Atmospheric Pressure
Why is mercury, a toxic substance, used and not water, for example, in a barometer. 10.3 m Because of its high density, mercury only rises 0.76 m due to atmospheric pressure. A column of water (lower density) in a barometer would be 10.3 m high
P 1 V 1 = P 2 V 2 Boyle s Law P 1 and V 1 are the original pressure and volume and P 2 and V 2 are the final pressure and volume The product of the pressure and volume for a given mass of gas stays the same as long as the temperature doesn t change.
Bouyancy in Air Any object that has a mass less than the mass of an equal volume of surrounding air will rise. In other words, objects that are less dense than the air around it will rise.
Bernoulli s Principle When the speed of a fluid increases, the pressure drops. We are talking about the pressure IN the fluid not the pressure on things the fluid ACTS on.
Bernoulli s Principle Bernoulli s Principle explains why the wings of an airplane have LIFT and the plane can fly. The air travels faster on the upper side of the wing meaning there is less pressure on the upper side than the lower side so the wing rises. LIFT
1. This room (H9) has dimensions of 6 meters (wide) by 8 meters (long). A.What is the weight of the air on the floor? B. What is the air pressure on the floor? 2. Squeeze a balloon to a third of its volume, by how much will the pressure inside the balloon increase? Double the pressure on the balloon, by how much will its volume decrease? 3. A scuba diver 10.3 m below the surface of the water breathes compressed air into her lungs. If she holds her breath while retuning to the surface, by how much will the volume of her lung s increase?
PHASE CHANGES Description of Phase Change Solid to liquid Liquid to solid Term for Phase Change Melting Freezing Heat Movement During Phase Change Heat goes into the solid as it melts. Heat leaves the liquid as it freezes.
PHASE CHANGES Description of Phase Change Liquid to gas Term for Phase Change Vaporization, which includes boiling and evaporation Gas to liquid Condensation Solid to gas Sublimation Heat Movement During Phase Change Heat goes into the liquid as it vaporizes. Heat leaves the gas as it condenses. Heat goes into the solid as it sublimates.
B. Phase Properties Phase Solid Liquid Gas Particle Properties Proximity Energy Motion Volume Shape close little vibrational definite definite close moderate rotational definite indefinite far apart a lot translational indefinite indefinite
B u t w h a t h a p p e n s if y o u r a is e th e te m p e r a tu r e to s u p e r -h ig h le v e ls b e tw e e n 1 000 C a n d 1,000,000,000 C? W ill e v e r y th in g ju s t b e a g a s?
STATES OF MATTER PLASMA A plasma is an ionized gas. A plasma is a very good conductor of electricity and is affected by magnetic fields. Plasmas, like gases have an indefinite shape and an indefinite volume. Plasma is the common state of matter
STATES OF MATTER SOLID LIQUID GAS PLASMA Tightly packed, in a regular pattern Vibrate, but do not move from place to place Close together with no regular arrangement. Vibrate, move about, and slide past each other Well separated with no regular arrangement. Vibrate and move freely at high speeds Has no definite volume or shape and is composed of electrical charged particles
S o m e p la c e s w h e re p la s m a s a re fo u n d 1. Flames
2. Lightning
3. Aurora (Northern Lights)
T h e S u n is a n e x a m p le o f a s ta r in its p la s m a s ta te
COLD PLASMA
COLD PLASMA PEN