# Page 1 Science Study Guide for the TASC

## How to prepare for the TASC Science Test

### General Information

The TASC Science Test covers topics covered in physical science classes, such as chemistry, astronomy, geology, and physics. The remainder of the questions concern biological science ideas that are mostly from biology instruction.

Here, we provide the basics. If there are any topics you do not understand fully, you will need to seek further explanation from online sites, textbooks, and/or high school equivalency classes.

Note: Concepts from life and earth sciences are more heavily emphasized on this test than those from physical sciences, but you should have a firm grasp of all of these scientific ideas.

## Physical Science Topics

### Matter

#### The Periodic Table

The periodic table organizes the chemical elements according to their atomic structure and chemical behavior. The smallest atoms are at the top and the largest ones at the bottom. Atoms increase in size from left to right in each row. Elements in the same column have similar atomic structure, usually because the number of electrons in their outermost shell is the same. This gives elements in each column similar chemical properties and reactions.

#### Simple Chemical Reactions

Simple chemical reactions are based on the number of electrons in the outer shell. Atoms will donate, accept, or share atoms so that they end up with 8 electrons in the outer shell (the exception is Hydrogen whose outer shell has 2 electrons). For example, sodium ($Na$) has 1 electron in the outer shell and chlorine ($Cl$) has 7. One atom of sodium will donate an electron to 1 atom of chlorine, forming sodium chloride, $NaCl$. Oxygen ($O$) has 6 outer electrons and will accept or share 2 others. Hydrogen ($H$) has only 1 outer electron, so 2 atoms of $H$ are needed to complete the outer shell of $O$, resulting in water, $H_2O$.

#### Electrical Forces Between Particles

Electrical forces occur between particles. Negative and positive charges act on the particles to attract them to and repel them from each other. The strength of these forces will determine the phase (solid, liquid, gas) of a substance and properties such as melting and boiling points. Stronger attractive forces require higher temperatures to separate the particles. For example, substances with strong attractive forces between the molecules will tend to be solid at room temperatures and have a higher boiling point.

#### Energy in Chemical Reactions

A chemical reaction may require a net input of energy or it may yield a net output of energy. If the energy contained in the chemical bonds (bond energy) of the reactants is greater than the bond energy in the products, the reaction will release energy. If the products have a greater bond energy than the reactants, the reaction will consume energy. Energy is conserved, so the energy consumed or released will match the difference in energy between reactants and products. Note that many reactions require an initial activation energy, even if they eventually release energy.

#### Temperature and Chemical Reactions

The rate at which a chemical reaction occurs depends on the interactions between the reacting particles. There are 2 ways to speed up these reactions: increase the speed of the particles or increase the amount of particles so they find each other faster. The speed of particles is increased by increasing the temperature. Increasing the concentration of the reactants will increase the amount of particles.

#### Creating Equilibrium

Le Chatelier’s Principle states that if the equilibrium of a reaction is disturbed by changing the conditions, the equilibrium will move to counteract these changes. For example, if more reactants are added, the system will counteract this and increase the rate at which these extra reactants are converted into products. This principle can be used to manipulate reactions to yield products at a faster rate.

#### Showing Conservation of Mass

Mass can not be created or destroyed. Atoms interact during a chemical reaction and the their mass is unchanged by the chemical reaction. A balanced chemical reaction is a visual model showing that mass is conserved in a chemical reaction. For any atom in the reaction, the total number on the left side of the equation, before the reaction, is the same as the total number on the right side, after the reaction. Atoms are not created or destroyed in a reaction. The atoms only change how they are combined with other atoms.

#### Fission, Fusion, and Radioactive Decay

In fission, fusion, or radioactive decay, the actual structure of the atom changes and it gains or loses electrons, protons, or neutrons. If the number of protons changes, the atom is transformed into a different type of atom. Matter is converted directly into energy in these reactions. A very small amount of matter release an enormous amount of energy in these processes. This discovery was summarized in Einstein’s famous equation $E =mc^2$.

### Motion and Forces

#### Newton’s Second Law of Motion

Newton’s second law of motion describes the relationship between the net force on an object ($F$), its mass ($m$), and the acceleration of the object ($a$) as the mathematical relationship, $F = ma$. If we know any 2 of these properties, we can calculate the third one. If we plot these 3 quantities for a moving object, we will see a distinct pattern because of this relationship.

#### Momentum

The momentum of an object is defined as the product of its mass and velocity, $momentum = mv$. For any pair of objects with no outside forces acting on them, the total momentum is conserved. If these objects interact with each other, such as in a collision, any momentum gained by one of the objects is balanced by a loss of momentum from the other object.

#### Collision Force

When an object collides, its momentum changes. The change in momentum is caused by a force exerted for a duration of time. The product of the force and the time duration is called impulse, $impulse = Ft$. Since momentum is conserved, the impulse is equal to the initial momentum of the object. The product $Ft$ is constant for any given collision, and $F$ and $t$ balance each other. If the time of the collision can be increased, the force will decrease so that the product $Ft$ remains the same. Cushioning works to protect objects during impact because it lengthens the time of impact, thus reducing the force of impact.

#### Newton’s Law of Gravity and Coulomb’s Law

Newton’s law of gravity states that $F = \frac{Gm_1m_2}{d^2}$. $F$ is the gravitational force between the objects; $G$ is a constant; $m_1$ and $m_2$ are the masses of the objects, and $d$ is the distance between them. This formula shows that the force will increase if the masses of either object increases, and the force gets much smaller when the distance increases. If the distance increases by a factor of 3, the force decreases by a factor of $3^2 = 9$. This is known as an inverse square law.

Coulomb’s law for electrostatic force is very similar: $F = \frac{kq_1q_2}{d^2}$. In this, $q_1$ and $q_2$ represent the electrostatic charges; $k$ is a different constant; $F$ is electrostatic force and $d$ is the distance.

#### Magnetic Fields and Electric Currents

Magnetism and electricity are closely interrelated. A magnetic compass placed near a working electric circuit will change its heading, showing the presence of a magnetic field around the flowing electricity. A magnet moved through a coil of wire will produce an electric current. This can be seen if a bulb is connected in a circuit with the wire coil. This is the basis of how electricity is generated for use in homes and industries.

#### Molecular Structure and Design

Molecular structure and the electrostatic charges of molecules will often determine how a given material might function. Long, chained molecules such as cellulose in plants produce strong, light structures such as wood. Electrical properties of molecules will determine if they can be used as conductors or insulators. This is usually related to how well electrons can move within the material.

### Energy

Energy is commonly defined as the ability to do work. Energy content in molecular bonds will determine whether a particular reaction will occur. The conversion and transfer of energy is at the heart of biological and ecological processes and much economic activity.

#### Energy in a System

Energy is neither created nor destroyed. If the energy of one component of a system changes, this change can be accounted for by changes in other components in the system or by flow of energy into or out of the system. In principle, if all of these can be measured, it is possible to calculate the change in one component if all of the other changes and the energy flows are known. An energy budget for the system can describe this process quantitatively.

#### Particles and Energy

The total energy of an object is the sum of its energy due to motion (kinetic energy) and its energy due to its position. For example, a ball that has been thrown upwards has kinetic energy due to its motion, and potential energy due to its height above the ground. As it gains altitude, it loses speed and the kinetic energy decreases. However, since it is higher, it has gained an equal amount of potential energy, and the sum of potential and kinetic energy remains constant.

#### Energy Conversion

Energy can be converted from one form to another. For example, the chemical potential energy in a battery can be converted into electrical energy. The electrical energy might power a motor that converts electrical energy to mechanical energy to do work. However, these conversions are never 100% efficient. Some energy is always lost as heat energy. The efficiency of a process is the ratio of the total useful energy output compared to the original energy input.

#### Thermal Energy

Thermal energy will always move from areas of higher temperature to areas of lower temperature. If two objects of different temperatures are in a closed system (heat cannot enter or leave), thermal energy will flow from the hotter to the cooler object, and the result will be an intermediate temperature. If liquids of different temperatures are mixed, the resulting liquid will be an intermediate temperature.

#### Interactions with Electric and Magnetic Fields

Objects that interact through electrical charges or magnetic fields can either attract or repel each other. Opposite charges or magnetic poles attract; similar charges or poles repel. These forces follow an inverse square law and diminish rapidly when the distance between the particles increases. When the distance gets too great, the force is so weak that it will not affect the motion of the particles. Less than this distance, there is a zone where the particles will not be able to stay. They will be repelled farther away until the force is too weak to affect them or they will be attracted to each other the distance between them is zero.

### Waves and Technology

Light, radio, and microwaves are all forms of electromagnetic radiation. Along with sound, they travel as waves. Understanding the nature of waves was vital in making widespread use of sound waves and electromagnetic radiation in our modern technologies.

#### Frequency, Wavelength, and Speed

For any wave, the speed of the wave is the product of its frequency and its wavelength. If you know any 2 of these variables, you can calculate the third one. The speed for a wave is a constant in any given medium. For example, the speed of sound waves in air is 330 to 350 meters per second, depending on the temperature. The frequency and wavelength for any sound will multiply out to this constant speed, no matter what the pitch, or frequency of the sound, is.

#### Digital Transmission and Storage

Digital transmission and storage of information is done by encoding the information as a series of 0s and 1s (binary code). The code itself does not degrade over time, as might happen with the pages of a book. Digital information can be copied and transmitted repeatedly without any loss. Each copy is just as high quality as the original. Digital information can easily be stolen and it is also very easy to erase by accident.