The velocity of an object will not change unless the force or forces acting upon it are

not in balance.

INERTIA

WHAT ARE CHEMICAL REACTIONS?• Now that we know the how and why of chemical bonding, we

can look at some chemical reactions. Chemical reactions happen all around us: when we light a match, start a car, eat dinner or walk the dog. A chemical reaction is the pathway by which two substances bond together.

WHAT ARE ELEMENTS AND ATOMS?• All matter, everything that we can see and touch, is composed of just over 100 elements

in different combinations. For example:

• Water is a combination of two elements: hydrogen and oxygen.

• Table salt is composed of two elements: sodium and chlorine.

• Another atom is the smallest particles of an element that still retains the properties of that element. Atoms cannot normally be broken down any further.

ELECTROMAGNETIC WAVES • Light, microwaves, x-rays, and TV and radio transmissions are all

kinds of electromagnetic waves. They are all the same kind of wavy disturbance that repeats itself over a distance called the wavelength.

NEWTON’S 3ERD LAW OF MOTION• For every action there is an equal and opposite reaction.

This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard

WHAT IS MEANT BY THE CONCENTRATION OF A SOLUTION?• In chemistry, the concentration of a solution refers to the amount of a solute in a

solvent. When sugar is dissolved in water, sugar is the solute and water is the solvent.

WHAT IS SYMBIOSIS?• The word “symbiosis” comes from the Greek, meaning living (biosis) together (sym). It

refers to two or more organisms of different species that form close and long-lasting relationships that benefit one or both species.

WHAT IS EVOLUTION?• Evolution refers to the theory of natural selection, first put forth by Charles Darwin in the

19th century. He recognized that whole population of organisms could change over time, becoming larger, smaller, faster, or better suited to the habitat in some way.

WHAT IS DENSITY?• Density is the degree to which molecules are packed together. For example, ice is less

dense then water.

WHAT IS THE LIFE CYCLE OF THE CELL?• The five stages of the cell’s life cycle:

• Interphase

• Prophase

• Metaphase

• Anaphase

• Telophase

HOW ARE PLANT AND ANIMAL CELLS SIMILAR AND DIFFERENT?• Similarities

• Carry all the genetic material of the organism to which they belong

• Break down food and convert it to energy

• Produce various enzymes and proteins as required

• Are capable of reproducing by division

• Differences

• plant cells are surrounded by cell walls made of cellulose

• Plant cells contain chloroplasts, which use chlorophyll to convert water and carbon dioxide into simple sugars

WHAT IS THE ROLE OF PRODUCERS IN AN ECOSYSTEM ?• Producers are the plants and other photosynthesizing organisms in an ecosystem.

Producers are the only organisms capable of harnessing the energy of sunlight and converting it into a form that living cells can use. Without the producers to harness energy entering the system, all consumers would eventually starve and die.

WHAT IS CONTINENTAL DRIFT?• The continents we are familiar with today-North and South America, Europe , Africa, Asia,

Australia, and Antarctica-did not always exist in the same position. Because of activity far below the earth’s surface, in some places magma flows to the surface and causes the crust to spread apart. In other places, some of the earth’s crust is forced under another position. This very gradual process means that over many millions of years some continents can drift farther apart while others can move closer together, split, or even collide.