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Physical Science

THE ATOM

The atom is the smallest unit of all physical matter.  Everything is made of atoms. It would take billions of atoms lined up in a grid to cover your screen right now.

An atom contains three component particles.

1.      The proton has a positive (+) charge.

2.      The neutron is neutral.  It has no charge

3.      The electron has a negative (-) charge.

The nucleus, or center, of the atom is made up of protons and neutrons.  Electrons occupy a region around the nucleus.

Atoms can have an electrical charge when the number of electrons does not equal the number of protons.  A charged atom (one that loses or gains electrons) is known as an ion.  If an atom has a higher proportion of electrons, then it is a negatively charged ion (cation).  If an atom has a higher proportion of protons, then it is a positively charged atom (anion). All atoms have a nucleus that contains both protons and neutrons. The total amount of protons and neutrons gives us the mass number of the atom. The total number of protons alone gives us the atomic number of the atom.

FORMS OF MATTER

There are three basic states of matter:  Solid, liquid and gas. Anything that takes up space, has mass, and resists change is called matter.

For example:

Water is liquid at room temperature

It is solid (ice) at water’s freezing point (31 degrees Fahrenheit, 0 degrees Celsius).

It is gas (water vapor) at water’s boiling point (212 degrees Fahrenheit, 100 degrees Celsius).

Different substances have different boiling and freezing points.  Oxygen is gaseous at room temperature.  Iron is frozen as a solid at room temperature.

There is a fourth form of matter called plasma, but it occurs only at extremely high temperatures, like those found on the sun. Plasma consists of high-energy, ionized particles.  It is best described as ionized gas. Most of the matter in the universe is in the state of plasma.

ENERGY

Energy cannot be created or destroyed. It can change forms but never ceases to exist. Heating up water is an example of using energy.  In this case, it is heat energy.  When you heat water, you are actually making the molecules of the water move faster.  When something is in motion it is said to have kinetic energy.

Matter can be converted into energy and vice-versa.  Energy can be stored up to be used later.  We call this potential energy.  An example of stored, potential energy is fuel.  Any fuel has complex and ordered chemical bonds that are broken down when the energy is used.

The law of conservation of energy states that since energy does not get destroyed, it is always somewhere. It is said to be conserved. Because of this, the total energy of the universe remains constant.

Another characteristic of energy is that it is always getting dispersed.  The dispersal or spreading around of energy is known as entropy.  Another way to think of the spreading of energy in a system is to think of there being a tendency toward less order or disorder.

CHEMISTRY

Chemistry is one of the oldest branches of science. It deals with chemicals or compounds and their interactions.  The most basic chemicals are the elements.  Elements are substances that cannot be broken down any further at the molecular level.

Table salt, for example, is a compound made up of sodium and chloride (a form of chlorine).  One could separate the sodium from the chlorine.  But one could not separate the sodium or chlorine into constituent components.  They are elements.

One could also do the reverse.  That is, one could combine the elements sodium and chlorine to create sodium chloride (table salt).  This is a chemical reaction where individual sodium atoms actually combine with chlorine atoms to create sodium chloride molecules.  

Click Here to view the full-size Periodic Table of Elements
periodic table of elements

The Periodic Table of Elements lists all the known elements. It is divided into periods (the rows), groups (the columns), and families. The study of the behavior of matter is based on the abilities of the elements to bond. Bonding is a process in which the elements transfer and share electrons in order to form compounds and other matter.

2

He

Helium

4.003

- Atomic Number:  The number of protons in the atom

- Symbol

- Name

- Atomic Weight

A mole is a unit of measure that is a specific number of atoms of an element.  Since atoms are of different size as we move along the periodic table, the same number of atoms of one element will be heavier than the same number of another.

The number of atoms in a mole is approximately 6.0221415 × 1023 (known as Avogadro’s number)

One mole of carbon (atomic weight =12) would be 12 grams while one mole of copper (atomic weight=63.546) would be 63.546 grams.  And if you could count the individual atoms in each quantity they would be about the same, Avogadro’s number.

Question:

1. On the periodic table, which of the following do elements increase in?

A. Atomic structure

B. Number of energy levels

C. Mass number at energy levels

D. Both mass and number of energy levels

E. Only mass

Answer: D

SOLUTIONS

A solution is a state where one substance is dissolved into another. The substance that is dissolved is called the solute and what it is dissolved into is the solvent. Forces of attraction between particles are what produce a solution. The bonds produced by these forces of attraction as well as the temperature will determine the solubility of the solute.

An example is salt dissolved into water.  It forms a salt water solution

A solution is said to be saturated when the amount of solute is the maximum amount the solvent can take.

The saturation level of a solvent can be raised by heating it.

Example:


Viscosity is the measure of the internal resistance of a fluid to flow. For example, water is less viscous than motor oil. The viscosity of a fluid will change with temperature. Look at the graph below for an illustration of how the viscosity of oil changes with temperature.

Under which situation will the oil’s viscosity increase?


A. As temperature goes down

B. When mixed with water

C. As volume goes down

D. As flow goes up

E. As resistance stabilizes

Answer: A

NEWTON’S LAWS OF MOTION

Isaac Newton studied the nature of physical objects around us.  A common story that is told about Newton is that watching an apple fall from a tree helped inspire his thoughts on gravity.  While there is no way of knowing how true this is, it does illustrate an important point about all the objects we see around us.  That is there is some unseen force pulling everything down toward the earth.

Newton came up with three laws of motion which form the basis of how we understand motion and force today.

Newton’s 1st law of motion:  Unless acted upon by a force, objects at rest tend to stay at rest and objects in motion tend to stay in motion at the same velocity and in the same direction.

This is also known as the law of inertia, the idea that an object will tend to keep doing what it is doing.

Now, your common sense will tell you that if you throw an object at the sky it will not go flying off into space at a constant speed.  And this might seem to contradict Newton’s law.  However, everyday objects on the surface of the earth are acted upon by gravity and air resistance.

A clearer example of inertia would be to think of your body in a vehicle.  Or, better yet, a drink with no lid that you are holding in a vehicle.  If you are stationary and then start moving, the liquid in the cup tends to stay in the same position.  And the result is that it spills over the back of the cup.  Once the liquid is in motion at a constant speed and you brake to slow down, the liquid tends to maintain that speed and may spill over the front of the cup as it tries to maintain that speed.

An object, such as a rock traveling through the airless vacuum of space, will maintain its speed and direction indefinitely, meaning forever, until it encounters a force.

Velocity (v) is the rate of change of distance over time.

v = distance/time

If George walks 10 meters in 5 seconds George is walking at 2 meters per second.

If he then starts to jog and covers 20 meters in 5 seconds, his velocity is now 4 meters per second.  He has changed his velocity, increased it by 2 more meters per second.

The speed of sound is 775 miles per hour.

Light travels at 186,282.4 miles per second.

A change in velocity is known as acceleration (a).

a          =         v1 – v2

                                         t

                        =          meters/second

                                           second

                        =          m  . 1

                                     s     s

                        =          m/s2


Newton’s 2nd law of motion: Force = mass * acceleration.  The force on an object is equal to the mass of the object times the acceleration the object is undergoing.

            F          = m * a

                        = kg * m/s2

Newton’s 3rd law of motion: Every action has an equal and opposite reaction. This is explained in the push or pull that one body exerts on another body, which is also called force.

For example, a space vehicle fires a jet in one direction to make it go in the opposite direction.

Momentum is a concept like force.  It depends on the mass of an object.  But instead of looking at how much the object is being pushed, we look simply at how fast the object is traveling.

Momentum = mass * velocity

When a ball knocks into another ball, it transfers its momentum to that object.  If a larger ball hits a smaller ball, that smaller ball will go a lot faster than the larger ball did.

Question:

Which object has more momentum?

A. a 3000 kg car traveling at 30 km/s

B. a 30 kg cannon ball traveling at 300 m/s

C. a 30000 train gravelling at 3 km/s

D. a 3 milligram bullet (0.003 kg) bullet traveling at 3000 km/s

E. a 3,000,000 kg house standing still

Multiplying the mass times the velocities provides us with answer A. being the largest at a momentum of 9000,000 kg m/s

WAVES

A wave can be thought of as a traveling vibration. There are all kinds of waves: sound waves, light waves, and water waves.  Waves are caused by a disturbance in a medium.  Waves carry energy. A wave is often described as a “wiggle in space and time.”

Every wave has certain characteristics

A wave is measured in wavelengths. The wavelength is the distance from one crest to another.  Amplitude is how high (crests) and low (troughs) the wave travels from the center line.  A larger amplitude means the wave is carrying more energy.

The frequency is how many cycles, or repetitions, a wave goes through in a second. The unit of frequency is the Hertz, which is cycles per second.

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