Download 8th Grade Comprehensive Science

8th Grade Comprehensive
Science
Mid-Term Exam Review
2015
What we learned..
• Big Idea 1: The Practice of Science
• Big Idea 2: The Characteristics of
Scientific Knowledge
• Big Idea 3: The Role of Theories,
Laws, Hypotheses, and Models
• Big Idea 4: Science and Society
• Big Idea 5: Earth in Space and Time
The Practice of Science
• Scientific Inquiry is an activity requiring
many steps.
– Formulating an investigable question
– Planning an investigation to answer the
question
– The collection of appropriate data
– Drawing a conclusion based on the data
– Communicating the results of the
investigation
The scientific process does not
always follow the scientific method
• Other types of investigations include
observational studies
• Scientists must remain creative, not only
in their methods and processes, but also
in their questions and explanations
• Scientists may use a variety of models
such as physical or computer to simulate
things that are too dangerous, expensive,
big or small.
Scientific Argumentation
• Scientists must be prepared to debate or
validate the results of their scientific
inquiry.
• This is an important part of generating
new ideas and communicating results.
Observation vs. Inference
• Observation
• Inference
• Noting a fact or
• Arriving at a
occurrence
conclusion based
• Using one’s senses to
on an observation
perceive something
• An assumption
without any
based on
assumptions.
probability.
• Ex: The boy is
running at 5 pm.
• Ex: The boy is
running home for
dinner
A Science Experiment:
• A student asks the question: What fertilizer
will make my plant grow taller in one month.
• The student designs an experiment: 4
identical plants, in the same soil, in the same
size container, receiving the same amount of
light.
• 3 brands of fertilizer, brand a, brand b, brand
c.
• The student has seen several commercials
for brand b, does some research on all the
brands.
An experiment continued
• Based on the research, the student states
a hypothesis: “Brand B will make the
plant grow taller in one month than the
other brands.”
• The student carries out the experiment:
– Measures and records the starting height of
each plant.
– Gives each plant the same amount of soil,
water and sunlight keeping as many variables
constant as possible
An Experiment continued:
• The student puts equal amounts of each
fertilizer on different plants. One plant gets
no fertilizer. This is the control. (the
independent variable is not applied-used
for comparison)
• The type of plant, the kind and amount of
soil, the container, the amount of water,
fertilizer, and sunlight are all constants.
(the factors that must stay the same)
• The fertilizer brands are the independent
variable. (The factor being tested)
An Experiment continued
• The student gives each plant equal
amounts of water and measures each
plant carefully every three days for a
month. The amount of growth is the
Dependent Variable (What is being
measured)
• The student takes organized notes and
details the growth of each plant on a table.
• At the end of 30 days, the student is ready
to analyze and interpret the data.
Drawing a conclusion
• The student finds the plant that received
fertilizer A grew taller than the other plants
in 30 days.
• Has the student finished the project?
What must every experiment be in order to
be considered valid?
Repeatable!
• In order to be a valid experiment, a
scientists must conduct multiple trials.
• Other scientists must be able to perform
the same experiment.
• If after several trials, Fertilizer A continues
to produce the most growth, the scientist
states that the hypothesis was NOT
supported. (A hypothesis is never right
or wrong, it is either supported or not
supported by the evidence/data of the
experiment!)
Does this mean the experiment
was a failure?
• No! The student has acquired valuable
information.
• The student can now modify (change) the
hypothesis to reflect their new
knowledge.
• Based on this new information, the scientist
can perform further studies possibly using a
different type of plant or changing another
variable.
• A negative result can lead to further
investigation!
Empirical Data vs. Pseudoscience
• Empirical Data
• Obtained through
experimentation
• Provable through
experimentation
• Pseudoscience
• A theory or claim having
no scientific basis
• “pseudo” is Latin for false
Empirical data or pseudoscience?:
You see a commercial that says you will look
younger if you use their skin cream.
Science is knowledge of the
physical or material world gained
through observation and
experimentation
• Science can not explain or answer every
question about the supernatural, art,
philosophy, religion, ethics, or politics.
• Science can supply information to help
people make decisions. Ex: Cloning
• Political, social and economical concerns
can also effect science. Ex: ending the
space program in Florida
The Roll of Theories, Laws,
Hypotheses and Models
• Theories are well tested scientific
beliefs. They are believed to be true but
could change or modify if new information
were to be obtained.
• For example: For many years, people
believed the Earth was the center of the
solar system ( Geocentric model). This
theory changed when the telescope was
invented. (Heliocentric model)
Theories in science Have:
• Multiple lines of evidence
• Have been tested over time
• Are generally accepted as “true” by
scientists in that field
• Are predictive (can be applied to future
events)
Scientific Law
• Scientific laws are based on things that
do not change. They do not have to be
explained.
• Examples: the law of gravity, the law of
conservation of matter, the law of
conservation of energy, Newton’s laws,
etc.
Space!
• Our Solar System:
• There have been two models of the solar
system, heliocentric and geocentric.
• Our Sun is just one of the billions of stars in
the Milky Way galaxy.
• The distance between planets is very small
when compared to the distance between
stars.
• Nothing in our solar system is a light year
away.
Distance in Space
• Within our solar system we measure
distance in AU’s, or Astronomical Units.
• One AU is equal to the average distance
between the Earth and the Sun or
150,000,000 km.
• The inner planets are fairly close together
whereas the outer planets are very far
apart.
• The inner planets are all small and rocky.
• The outer planets are large and gaseous.
Objects in our Solar System
• In addition to the Sun and planets, our
Solar System contains:
• Moons- they stay in orbit around individual
planets.
• Asteroids- they are found in the asteroid
belt between Mars and Jupiter. They orbit
the Sun, not planets
• Comets- originate in the Kuiper Belt, travel
from the edge of the solar system, around
the sun, and back to the edge again.
• Meteors, Meteorites, Meteoroids
Gravity’s Impact in Space
• Gravity is responsible for the formation of
Stars and Planets
• Gravity keeps planets in orbit around the
Sun
• Gravity keeps moons in orbit around
planets
• Gravity keeps stars in orbit around the
center or galaxies
Earth Orbits the Sun, the Moon
Orbits the Earth
• How does this affect us?
• As the Earth orbits the Sun, sometimes it is
closer to the Sun (January), sometimes further
away (July). This does NOT cause us to have
seasons.
• We experience season’s on Earth because the
Earth is slightly tilted on it’s axis.
• The hemisphere tilted toward the Sun
experiences summer, the hemisphere tilted
away experiences winter.
The Moon Orbits Earth
• As the moon moves around Earth, varying
amount of it’s surface shows.
• This is because the moon does not
produce it’s own light. It only reflects
the light from the Sun.
• We call these varying amounts of light
phases. New moon, waxing crescent, 1st
quarter, waxing gibbous, Full moon,
waning gibbous, 3rd quarter, waning
crescent.
• The moon’s gravity causes tides on
Earth
Eclipses
• Sometimes the Moon moves into the Earth’s
shadow. This is called a Lunar Eclipse. Earth’s
shadow moves over the moon.
• Rarely, the moon casts a shadow on Earth. This
shadow is called the Umbra. When this
happens, the Sun is momentarily blocked from
view from Earth.
• The penumbra is the shadow around the umbra.
People in this area see a partial eclipse.
• Solar eclipses are rare because the moons
shadow is very small.
Outside of our Solar System
• The distance to everything outside of our solar
system is measured in Light Years.
• One light year is the distance light will travel in
one year. 186,000 miles per second or
300,000 km per second
• The closest star to our solar system is over 4
light years away.
• That means that when we look at that star, we
are seeing it how it appeared 4 years ago.
• Some of the stars we see in the night sky are
millions of light years away!
The magnitude of Stars
• Some stars in the sky appear to be
brighter than others. Sometimes they
only appear brighter because they are
closer.
• How bright a star really is, is it’s
Absolute Magnitude or Absolute
Brightness
• How bright a star appears from Earth
is it’s Apparent Magnitude.
The Sun and other Stars
• Stars produce light and heat through Nuclear
Fusion.
• Our Sun has many layers. Since the layers are
not solid, they rotate at different rates.
• Convection occurs at one layer which is the
rising and falling of gas.
• On another layer sunspots, prominences, and
solar flares occur.
• The color of a star indicates how hot the star
is.
• Blue stars are the hottest
• Red stars are the coolest
How stars are classified
• Stars can be classified on the HR diagram
according to their magnitude and
temperature.
• The stars the fall across the center of the
diagram are called “main sequence” stars.
• Our sun is a very average main
sequence star.
Electromagnetic Spectrum
• The electromagnetic spectrum makes
up the radiation that is sent to Earth from
the Sun.
Electromagnetic Spectrum
Continued..
• Although we can not see them all, these
waves are all around us:
– Radio waves carry communication and
television signals
– Microwaves also are used for communication
– Infrared waves are used by remote controls
– Ultraviolet waves cause sunburn and can
cause skin cancer
– X rays are used for medical purposes
– Gamma rays are used to kill cells
Electromagnetic Spectrum
Continued..
• Notice that radio waves have the largest
wavelength and that gamma rays have the
smallest.
• Waves with smaller wavelengths are
more dangerous to humans.
• Many of the dangerous waves from the
Sun are blocked by the ozone layer in
Earth’s atmosphere.
The Universe
• The Universe is made up of clusters of
billions of galaxies.
• Our Sun is in the Milky Way Galaxy
• Each Galaxy is made up of clusters of
billions of stars.
• Not all galaxies are the same shape, but
they all rotate around their centers.