Physical Science
Matter- the "stuff" that all objects and substances in the univers are made of.
Physical properties of matter
Density- The amount of matter in a given volume(mass per unit volume)
Ductility- the ability to be pulled inot a thin strand, like a wire.
Malleability- the ability to be pressed or pounded into a thin sheet.
Boiling Point- the temperature at which a substance changes from a liquid to a gas.
Melting Point- the termperature at which a substance turns from a solid to a liquid.
Electrical Conductivity- how well a substance allows electricity to flow through it
Solubility- The ability to dissolve in another substance.
States of Matter
Solid
Keeps its shape and volume
Liquid
Takes on the shape of the container
Keeps the same volume, in a container or not
Gas
Takes on the shape and volume of its container
Can flow
Atoms
The smallest particle into which an element can be divided and still maintain the properties of that element.
Atomic Structure
Nucleus- the center of the atom where protons and neutrons stick together.
Protons- Positively charged particles loacted in the nucleus
Neutrons- Located in the nucleus, electrically neutral.
Isotopes- atoms of the same element that have different numbers of neutrons.
Electrons- Negatively charged particles found outside the nucleus of an atom.
Evolution of Atomic Theory
Greek Philosopher Democritus proposed the existence of atoms in 440 B.C.
British Chemist John Dalton proposed that all substances were made of atoms- small, hard dense spheres that could not be created, destroyed, or altered.
British Scientist J.J. Thompson proposed that atoms themselves were made up of smaller particles. He discovered that atoms contained negatively charged particles.
Ernest Rutherford proposed that atoms had a dense, positively charged nucleus surrounded by electrons in 1911.
In 1913, Danish Scientist Niels Bohr furthered the theory by suggesting electrons revolved around the nuclues in circular paths, called orbit.
The current model is known as the electron cloud model, electrons surround the nucleus, traveling in regions called clouds.
Elements, Molecules and Compounds
Elements are the simplest form of matter. There are 110 known elements in the universe.
Molecules- the combination of two or more atoms.
Diatomic Molecules- a molecule that only contains 2 atoms
Compounds- elements that are found in combination with other elements.
Example: Water is 2 Hyrdogen and 1 oxygen. H20
Forces and Motion
Force- a push or pull on an object.
Gravity- the force of attraction between objects that have mass
The strength of gravity depends on the mass of the objects and the distance between them.
Mass- a measure of the amount of "stuff" in an object. The greater the mass of either object, the stronger the gravity between them.
The closer together the objects, the stronger the gravitational force.
Electric Force- associated with unmoving charges.
Positive and negative charge attracts, positive and positive or negative and negative repels.
Magentic Force- associated with moving electric charges.
Magnet- any material that attracts iron.
Friction- the force that opposes motion between two surfaces that are in contact with each other. It could prevent motion from starting or oppose motion in progress.
Balanced and Unbalanced Forces
Balanced force produces no change in the motion of an object
Unbalanced force produces change in the motion of an object
Motion
Newton's Laws of Motion
Newtons's First Law of Motion
An object will not change its motion unless a force acts upon it
Newton's Second Law of Motion
The force of an object is equal to its mass times acceleration
Newton's Third Law of Motion
When two objects interact, they apply forces to each other of equal magnitude and opposite direction.
Machines
Inclined Plane
A flat surface that slopes to make an incline. This simple machine does not move. Example, ramp for wheel chair accessibility
Wedge
An inclined plane that moves to fulfill its purpose. Example, axe or door wedge
Screw
A long cyndrilacal piece of metal that holds two materials or objects together.
Lever
A long rigid bar that rests on and pivots around a support.
There are 3 types of levers, first-class, second-class, and third-class. The classification is in regard to the location of the fulcrum
Wheel and Axle
An axle is inserted through the middle of a wheel. Any force applied the wheel gets transferred to the axle and vice versa.
Pulley
A wheel with a rope or chain attached. the wheel rotates around a fixed axle and the rope rides the groove of the wheel making it easier to lift heavy or awkward objects.
Energy
Forms of Energy
Mechanical Energy
The energy an object has because of its motion or position
Kinetic Energy
The energy an object has because it is moving
Potential Energy
The energy an object has because of its position of shape
Thermal Energy
The energy related to the temperature of an object
Light Energy
The energy carried by light and other kinds of electromagnetic waves
Sound Energy
The energy carried by sound waves
Electrical Energy
The energy produced by electric charges
Chemical Energy
The energy stored in chemical bonds
Nuclear Energy
The energy contained in the nuclei of atoms
Waves- an oscillation that travels from one place to another with a certain velocity.
Mechanical waves are waves that travel through matter. Examples; sound waves, water waves.
Electromagnetic waves are waves that can travel through empty spaces. Examples; visible light, x-rays, radio waves.
Characteristics of waves
Amplitude- the distance a wave oscillates from its restion position.
Wavelength- the distance from any point on one wave to a corresponding point on an adjacent wave.
Frequency- the number of oscillations produced in a certain amount of time. Frequency is measure in hertz(Hz)
Wave speed- the distance a wave travels in a given amount of time.
Electricity and Magnetism
Laws of electric charges.
Like charges repel
+> <+
-> <-
Unlike charges attract
+< >-
The attractive or repulsive force between charged objects is called electric force. The strength of electric force between charged objects depends on the size of the charge and distnace between them.
Static Electricity- the build up of electric charge on an object by rubbing. Example; rubbing a balloon on your hair.
The sudden and brief flow of electrons is called static discharge. Example; touching someone and feeling a small zap, lightning.
Current Electricity is a continuous flow of electric charge
Direct current(DC) electricity is current in which the electric charge moves in one direction. Example; Batteries
Alternating current(AC) is current in which the electric charges flow in one direction, then in the reverse direction, over and over again.
Electric circuits- a path that electricity flows through. A closed circuit has no breaks in it, an open circuit has a break.
Parts of a circuit
Energy source- a battery with a negative and positive charged terminal.
Load- a device that the electric circuit is delivering the electrical current to. Example; light bulb.
Wires- used to connect the energy source(s) to the load(s).
Switch- opens and closes a circuit by bringing together or seperating two pieces of metal.
Magnet- any material that attracts iron. All magnets have two poles- a negative and positive pole. These poles are where the magnetic forces are the strongest.
A magnetic field is a region around a magnet that is affected by magnetic forces.
Electromagnetism- a magnetism resulting from electric charge in motion