Science Semester 1 8th grade

Observation

gathering information using your five senses

Inference

a conclusion reached on the basis of observation

weather

the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy

atmosphere

the envelope of gases surrounding the earth or another planet

ozone

a colorless, unstable, toxic gas with a pungent odor, formed from oxygen that is exposed to ultraviolet light. It is oxygen with atoms O3 vs. normal oxygen O2

Water vapor

Water in a vaporous form, especially when below boiling temperature and diffused in the atmosphere

density

mass per unit of volume (density = mass/volume)

pressure

the continuous physical force exerted on or against an object by something in contact with it

air pressure

the force exerted onto a surface by the weight of the air. Air pressure is measured in mb, inches of mercury, lbs/in2 and kPA.

Barometer

An instrument used to measure atmospheric pressure and helps forecasting weather

altitude

the height of an object or point in relation to ground or sea level

troposphere

the lowest region of our atmosphere and where the majority of our clouds and weather systems occur

stratosphere

the layer of our atmosphere that is above the troposphere and below the mesosphere, also known as the ozone layer because this is the area where most ozone resides

mesosphere

the region of our atmosphere that is above the stratosphere and below the thermosphere

thermosphere

the region of our atmosphere that is above the mesosphere and below what’s referred to as space (no atmosphere)

Ionosphere 

the layer of our atmosphere that contains a high concentration of ions and is able to reflect radio

exosphere

the outermost region of our planet’s atmosphere, after which you would be in space

wind

the perceptible natural movement of air, especially in the form of a current of air blowing from a particular direction

anemometer

an instrument for measuring the speed of the wind or any stream of gas

wind chill factor

the perceived decrease in air temperature felt by the body on exposed skin due to the flow of air

sea breeze

a breeze blowing toward the land from the sea, especially during the day, mainly due to the warmth of the land as compared to the sea

land breeze

a breeze blowing towards the sea from the land, especially at night, mainly due to the warmth of the sea as compared to the land

coriolis effect

an effect whereby a mass in a rotating system experiences a force acting perpendicular to the duction of motion and on Earth causes weather systems to deflect east in the northern hemisphere

jet stream

a band of very strong (80-275 mph) predominately westerly air currents flowing around the globe, several miles above the earth

bernoulli’s principle

as the speed of a moving fluid increases, it’s pressure decreases

evaporation

the changing of a liquid in a gas on the surface of that liquid

humidity

a quantity representing the amount of water vapor in the atmosphere

condensation

the conversion of a vapor or gas to a liquid

dew point

the atmospheric temperature below which water droplets begin to condense and dew or condensation can form

condensation nuclei

a small particle that water vapor condenses on in the atmosphere to form clouds

International System of Units

A system of physical units (SI Units) based on the meter, kilogram, second, ampere, kelvin, candela, and mole together with a set of prefixes to indicate multiplication or division by a power of 10

motion

the action or process of moving or changing place or position in relationship to a reference point

reference point

a point used to find or describe the location of something (common points - north, south, east and west)

Meter

the fundamental unit of length and is approximately 39.37 inches when compared to the US Customary Units

Speed

An object’s distance travelled in a given amount of time

velocity

an object’s speed in a given direction

acceleration

the rate of change of velocity per unit of time: Vf-Vo/1 = a

variable

a characteristic, number or quantity that increases or decreases over time. There are two types: Independent - changes other variables and Dependent: is changed by the independent variable

Force

a push or pull on an object resulting from the objects interaction with another object. Forces are reported in Newtons (N) and by using F=ma (Newton’s second law of motion)

Newton

the SI unit of force and is equal to the force that would give a mass of one kilogram an acceleration of one m/s/s

Net force

is the sum of all forces acting on a object and is capable of moving or accelerating an object

unbalanced forces

force that causes a change in the motion of an object

balanced forces

two forces cting in opposite directions on an object and are equal in size

friction

the resistance that one surface or object encounters when over or through another

static friction

the friction that exists between a stationary object and the surface it’s resting on. Static friction disappears when motion happens

sliding friction

type of frictional motion between two surfaces in contact and is affected by the typo of surfaces involved and the force pushing them together

rolling friction

the force resisting motion when a body rolls on a surface

fluid friction

the resistance to an object’s motion through a liquid or gas

gravity

the natural attraction between two physical bodies and is affected by how much mass the objects have and the distance that separates them

mass

a measure of how much matter is in an object

weight

the force of gravity on an object and is measured in Newtons in SI

free fall

downward fall of an object with only gravity acting on it (we disregard friction forces)

air resistance

the frictional force air exerts against any moving object and is always present in our atmosphere

terminal velocity

the constant speed a falling object reaches when the air resistance to motion prevents further acceleration (happens when the upward force = downward force or fluid friction = gravity’s pull)

Inertia

An object at rest stays at rest and an object in motion stays in motion until acted upon by an unbalanced force (Newton’s First Law of Motion)

momentum

mass in motion and is described by how difficult it is to accelerate an object to zero speed

Law of Conservation of Momentum

For every force, there is an equal but opposite reaction force (Newton’s third law of motion)