“Standard Model”
What our current understanding of subatomic particles is known as
Atom
building block of matter
Element
Material composed of only one kind of atom
How many elements are known?
- 90 occur naturally.
Every simple, complexing, living, or nonliving substance in the known universe is put together…
from a pantry containing less than 100 elements.
Atoms are so small that there are about…
10^23 atoms in a gram of water.
Atoms in body have been around since…
more than 4.6 billion years ago.
Brownian motion
perpetual jiggling of particles that are just large enough to be seen.
Brownian motion is evidence…
that atoms exist, as it results from the motion of neighboring atoms and molecules. They bump into the larger particles that we can see.
Molecule
Smallest particle of a substance consisting of two or more atoms that bond together by sharing electrons.
Molecules can be made up of…
atoms of the same element or of different elements.
Compound
Substance that is made of atoms of different elements combined in a fixed proportion.
Chemical formula
Tells the proportions of each kind of atom for a compound.
Compounds have properties different from those of…
the elements of which they are made.
Nucleus
Where almost all of an atom’s mass is packed into a dense central region.
Nucleons
Principal building blocks of the nucleus.
Neutrons
Nucleons in an electrically neutral state
Protons
Nucleons in an electrically charged state
Isotope
Atoms of the same element having different numbers of neutrons.
Deuterium
When proton is accompanied by a neutron
Tritium
When two neutrons are in a hydrogen nucleus.
Atomic number
The number of protons in the nucleus.
Ion
Atom with a net charge.
Shell model of atom
- electrons are pictured as orbiting in spherical shells around the nucleus.
- there are seven different shells, each has its own capacity for electrons
The arrangement of electrons in the shells around the atomic nucleus dictates…
the atom’s chemical properties.
Four phases of matter
Solid, liquid, gaseous, and plasma
Plasma
Consists of positive ions and free electrons. Phase exists only at high temperatures.
Crystals
Regular geometric shapes whose component particles are arranged in an orderly, repeating pattern.
The shape of a crystal mirrors the…
geometric arrangement of atoms within the crystal.
Density
Measure of how much matter occupies a given space.
density = mass/volume
The density of a material depends upon…
the masses of the individual atoms that make it up, and the spacing between those atoms.
Weight density
Amount of weight a body has per unit of volume.
weight density = weight/volume
Specific gravity
Standard measure of density. The ratio of mass (or weight) of a substance to mass (or weight) of an equal volume of water.
Elastic
Material that returns to its original shape after is has been stretched or compressed.
A body’s elasticity describes…
how much it changes shape when a deforming force acts on it, and how well it returns to its original shape when the deforming material is removed.
Inelastic
Materials that do not resume their original shape after being distorted.
Hooke’s Law
The amount of stretch (or compression), x, is directly proportional to the applied force F.
F ~ (change in)x
-law holds only as long as the force does not stretch or compress the material beyond its elastic limit.
Elastic limit
The distance at which permanent distortion occurs.
A horizontal beam supported at one or both ends is under stress…
from the load it supports, including its own weight. It undergoes a stress of both compression and tension (stretching).
Scaling
The study of how size affects the relationship between weight, strength, and surface area.
When linear dimensions are enlarged, the cross-sectional area (as well as the total surface area) grows as…
the square of the enlargement, whereas volume and weight grow as the cube of the enlargement.
As the linear size of an object increases, the volume…
grow faster than the total surface area.
Which five elements make up most living things?
Carbon, oxygen, hydrogen, nitrogen, calcium
Why are atoms too small to be seen with visible light?
Light is made up of waves, and atoms are smaller than the wavelengths of visible light.
Provide two kinds of evidence that atoms exist.
- Brownian motion of matter: results from the motion of neighboring atoms and molecules, which bump into larger particles we can see.
- Other evidence: atoms are observable with scanning electron and scanning tunneling microscopes.
A fluid is…
anything that flows. Both liquids and gases flow; so both are fluids and have some properties in common
Density links…
the properties of pressure and buoyancy
Liquids exert…
pressure. Pressure is NOT dependent on volume, but on depth.
Archimedes principle
The buoyant force on an immersed object is equal to the weight of the fluid it displaces. True for both liquids and gases.
Pascal discovered that if you apply pressure to a liquid in a closed system…
that pressure gets applied evenly across the entire liquid.
Which of the following statements are true?
a. Pascal’s principle was discovered in the seventeenth century.
b. The SI unit for pressure is named after Pascal.
c. Pascal’s principle is employed in a hydraulic press.
a and c are true
Pressure
= force/area
The pressure of a liquid at rest depends only on…
gravity and the density and depth of the liquid.
pressure due to liquid
= density * g * depth = pgh
Buoynacy
The apparent loss of weight of objects when submerged in a liquid.
Buoyant force
Net upward force exerted by a fluid on a submerged or immersed object.
When the weight of a submerged object is greater than the buoyant force…
the object will sink
When the weight is less than the buoyant force…
the object will rise to the surface and float
A submerged object’s…
volume - not its weight - determines buoyant force
Three rules for sinking and floating
- an object more dense than the fluid in which it is immersed sinks
- an object less dense than the fluid in which it is immersed floats
- an object with density equal to the density of the fluid in which it is immersed neither sinks nor floats
The principle of flotation states that…
a floating object displaces a weight of fluid equal to its own weight
Pascal’s principle
Describes how changes in a pressure are transmitted in a fluid.
Liquids are almost…
completely un-compressible
gases can be…
compressed a great deal
Why don’t we feel air?
- we are used to it.
- Air is a fluid, and, since fluids exert pressure in all directions, the air is exerting pressure on me from below as well as from above.
- The body is designed to have an equal amount of pressure pushing out from the inside.
Which of the following statements are true?
a. The amount of water that flows past any section of the pipe changes with pipe width.
b. The water will slow down in a wider part of the pipe.
c. The water will speed up in a narrower part of the pipe.
d. The amount and speed of the water in the pipe does not change.
b and c are true
Earth’s atmosphere consists of…
molecules that occupy space and extends many kilometers above Earth’s surface.
Earth’s atmosphere has no…
definite upper surface
Barometer
Instrument used for measuring the pressure of the atmosphere.
-The height of the mercury in the tube of a simple barometer is a measure of atmospheric pressure
Aneroid barometer
Instrument that measures variations in atmospheric pressure without a liquid
An aneroid barometer uses a…
small metal box that is partially exhausted of air. the box has a slightly flexible lid that bends in or out as atmospheric pressure changes.
Boyle’s law
Relationship between the pressure and volume of a gas.
Equation: P(1)V(1) = P(2)V(2)
Boyle’s law states that…
The product of pressure and volume for a given mass of gas is a constant as long as the temperature does not change.
Any object less dense than the air around it will…
rise
Bernoulli’s Principle
Relationship between the speed of a fluid and the pressure in the fluid.
-holds only for steady flow
Bernoulli’s principle in its simplest form states that…
when the speed of a fluid increases, pressure in the fluid decreases
Streamlines
Smooth paths, or trajectories, of the bits of fluid
Eddy
A changing, curling path. B
Lift
The upward force created by the difference between the air pressure above and below the wing
When lift equals weight…
horizontal flight is possible
What causes atmospheric pressure?
weight of air, just as water pressure is caused by the weight of water.
What would happen to Earth’s atmosphere without the sun?
The molecules in the atmosphere would eventually cool and end up as matter on the ground.
Below what level is 99% of the atmosphere of Earth found?
30km
Name three things that can cause variations in atmospheric pressure.
Differences in altitude, moving air currents, and storms.
Remember that you increase length, width and height by a factor…
of 10 so that increases volume (and thus mass) by 10,000X.
