What You Learned in 7th Grade
Scientific Methods
The Scientific Method
The scientific method is for learning about anything. The experiment—what many
people focus on—is only a part of learning something new.To complete the scientific
method correctly, you’ve got to think about several things. First, how will you find the
answer to your question? In other words, what steps will you use to find the answer?
1) Ask a question.
(What do you want to know, based on some observation?)
2) Create a hypothesis.
(What is your prediction of what you will find?)
3) Test your hypothesis.
(This is where you perform a controlled experiment.)
4) Analyze the results of your experiment.
(What did you observe during the experiment?)
5) Draw a conclusion.
(Based on what you observed during the experiment, how can you
answer your original question?)
6) Communicate the results.
(Letting other people know what you’ve learned is how we—as
human civilization—build knowledge.)
Let’s look at an example:
You want to know which type of soil is best for growing sunflowers. So,
you plant three sunflowers: one in the dirt from your backyard, one in the dirt in
your yard but with mulched fertilizer on top, and one in the dirt in your yard but
with Miracle Grow pellets poured into the hole you dug. You plant each
sunflower right next to each other so they get the same amount of sunlight and
water each day. You measure the heightof each sunflower each week using a
meter stick.
Question: What type of soil is best for growing sunflowers?
Hypothesis: I think that________because________
Controlled experiment:
Independent variable (the one you change, the cause): type of soil
Dependent variable (the one that gets changed, the effect): height
of the plant
Controls: amount of water, sunlight, yard dirt
Analysis:Here, I’d make a graph (like the one below) to display the data I
collected.
Conclusion: Mulched fertilizer is best for growing sunflower plants.
Even though the Miracle Grow works very quickly, it slowed down in
Week 4.
Communicate:Tell somebody!
The Engineering Design Process
The engineering design process is similar to the scientific method, but it’s meant
for building something new. To build something new, you should:
1) Identify a need.
(Why are building this thing? What is its intended benefit?)
2) Develop possible solutions.
(Like a hypothesis, you’re predicting what you could build to meet
that need. There are many possibilities.)
3) Build a prototype.
(Build a working model of the best possible solution).
4) Test the prototype.
(Make your product do what it’s intended to do. If it’s a plane, see
how it flies. If it’s a new kind of fertilizer, see how it helps plants
grow. This helps you identify unintended consequences).
5)Improve your design.
(Based on your test, you saw how well it completed its intended
benefit and observed any unintended consequences. Now, make it
do the intended benefit better, and minimize any negative
unintended consequences).
You can also engineer, or build, products for living organisms.
Adaptive bioengineered products permanently change an organism.
Ex: organ transplants, laser eye surgery, microchips in dogs,
vaccines
Assistive bioengineered products are not permanent; they help only for as
long as you “wear” them.
Ex: crutches, eyeglasses
Earth Science
The Layers of the Earth
We talked about two classifications for the layers of the Earth:
The three main:
And the five physical:
The earth’s inside layers help to shape its outside layer. The hot, dense solid inner core
generates heat—enough heat to melt the metal in the outer core into a liquid. This hot
liquid metal is hot enough to melt the rock around it—the lower part of the mantle, the
mesosphere. This hot rock rises through the mantle until it’s far enough from the core to
start cooling down. This cooler rock solidifies into the weak rock of the asthenosphere.
Furthest from the core is the coolest, most solid rock of the lithosphere (the crust is the
upper part of the lithosphere). The lithosphere is broken into pieces called tectonic plates
Plate Tectonics
The heat generated by the core creates a convection currentthrough the mantle. Hot
liquid rock rises from the mesosphere to the asthenosphere, and cool rock sinks from the
asthenosphere to the mesosphere. So, as a result, the asthenosphere moves. When it
moves, it carries the tectonic plates with it at a rate of a few centimeters per year. The
earth’s tectonic plates can move in three ways:
Convergent:
Boundary
Convergent
Result
Example
1. Folded Mountains
(continental-continental)
2. Volcanic Mountains
(continental-oceanic)
3. Volcanic Islands
(oceanic-oceanic)
1. Himalayas
2. Andes
3. New Zealand
Transform:
Divergent:
Transform
Divergent
Earthquakes
Sea-floor spreading
(where new oceanic
lithosphere is made)
San Andreas Fault
Mid-Atlantic Ridge
Rocks and Minerals
In part because of the convection currents inside the Earth and, therefore, the movements
of the tectonic plates, we find rocks and minerals (as well as water) on and in the Earth’s
crust.
Minerals
Minerals meet four criteria:
1) Minerals are solid.
2) Minerals are inorganic—the substances in the mineral were never at
any time alive (unlike coal, which is made from plant remains).
3) Minerals are naturally formed. A diamond found in a mine would be
considered a mineral, but a manufactured (human-made) is not.
4) Minerals have a crystalline structure at the atomic level.
We classify minerals in a variety of ways—by their color, luster, streak, special
properties, density (remember Archimedes!), cleavage or fracture (how they
break), and hardness. We measure hardness using the Mohs Hardness scale:
Rocks
Rocks are made out of a combination of minerals. Three types of rock exist:
igneous, metamorphic, and sedimentary. Though it’s called a rock “cycle”
because rocks are constantly being re-shaped, any type of rock can turn into any
other type of rock.
Life Science
This year, you learned the fundamental parts and processes of life. First, we learned
about the smallest unit of life—cells. We talked about the organs (organelles) of cells,
how cells have energy for those organelles to work, what they use that energy for
(making more cells), how cells know what to do (DNA), and how cells join together to
make the tissues, organs, and organ systems of large organisms. We often used plants as
an example for talking about these parts and processes.
Cells
Cells are the building blocks of all life and can be broken down into two main
categories:prokaryotes and eukaryotes.
We focused on eukaryotes (since they make up animals and plants) to explore the
different types of organelles.
Image
Function
Organelles
The control center for a cell.
Contains DNA
Nucleolus is in its middle.
Nucleus
Nucleolus
Inside the nucleus
Makes ribosomes.
Endoplasmic
Reticulum (ER)
Golgi
Ribosome
Mitochondrion
Attached to the nucleus
Transports proteins inside the cell
Rough (with ribosomes) and smooth (no ribs)
Packages and ships proteins outside the cell
Wraps proteins and molecules inside vesicles
Make proteins
More of this organelle than any other in the
cell
Creates energy (ATP) for the cell
Cellular Respiration happens here
Chloroplast*
Creates food for plant cells
Photosynthesis happens here
Lysosome*
Cleans waste out of cells
Membrane
Protective outer layer of all cells
Semipermeable so that only some substances
can pass through
Cells and Energy: Photosynthesis and Respiration
Cells need energy so that all these different organelles can function. In order to get
energy, they first need food. All cells get food from producers that perform
photosynthesis, so you could say that the source of energy for all life is the sun. Once
cells have food, they break it down in their mitochondria in a process called respiration
that creates energy.
Photosynthesis works like this:
Cellular respiration is the reverse of this equation. So, these two processes work
as a cycle to perpetuate cells’ ability to get food, and then energy from that food.
You might wonder how carbon dioxide and oxygen are traded between plant and
animal (or plant and plant) cells. You can find oxygen even where they are no
plants because of diffusion.
Diffusion means that particles (of oxygen, for instance) move from
crowded areas to less crowded ones.
Since the diffusion of water is so important for all cells, it’s given a
special name—osmosis.
Making more cells: cellular division and mitosis.
Cells need energy for lots of things, but one of those most important of those things is
making new cells. Living organisms are constantly making new cells to replace older
ones.
I Personally Made A Turkey Cry. (IPMATC)
Interphase, prophase, metaphase, anaphase, telophase, and cytokinesis are the stages
of cell division. The four middle stages make up the process of mitosis—how a cell
makes a nucleus for a new cell. In plants, the process looks like this:
Multicellular organisms need to make lots of cells so that they can join together to make
up tissue, which join to form organs, which make up organ systems. This allows
organisms to do much, much more than single-celled organisms since the cells are
specialized.
For instance, the human cardiovascular (or circulatory) system pumps blood—
and the oxygen and carbon dioxide it carries—to all our cells. The respiratory
system takes in the oxygen we need for cellular respiration to make energy and
gets rid of the carbon dioxide waste that is a product of respiration.
Heredity
You might ask how cells—with all their complicated parts, that do all these complicated
processes—know what to do. Well, they have instructions written in your DNA.
Your DNA, located in the nucleus of your cells, is made up of chromosomes—
long strands of DNA that each contains different genes, or traits.
Your DNA comes from your parents. All sexually reproducing organisms contain
exactly 50% of DNA from Mom and 50% DNA from Dad. Even if you look or
act more like one of your parents, each still gave you half of your DNA. This has
to do with genes.
For every gene, you receive a set of alleles from Mom and a set from
Dad. Alleles are either recessive or dominantso that their mixture (your
genotype) determines which trait you’ll have. We can predict these traits
using Punnett squares that show the probability the offspring of certain
parents will express a gene.
‘R’ is the dominant allele and ‘r’ is the recessive allele.
‘RR’ or ‘rr’ is a homozygous genotype. ‘Rr’ is a heterozygous one.
‘Round’ is one possible phenotype and ‘wrinkled’ the other.
Plant Reproduction
Gregor Mendel first discovered the principles of heredity—how dominant and recessive
traits are passed from parents to offspring. He performed experiments on pea plants since
he knew how they reproduce.
Flowering plants have both male and female reproductive systems. This structure
meant that Mendel could cross plants with different traits and then use a single
plant that to true-breed meaning both parent sex cells (from the same plant)
would have the exact same genotype. Because the offspring of true-breeding
plants weren’t always the same, Mendel discovered how dominant and recessive
traits work.
The pistil is the female reproductive system that creates eggs—ovules, the female
sex cell in plants.
Stigmas collect pollen. Pollen sticks here to start fertilization.
The pollen then travels down the styleto the ovary where ovules are made.
The stamen is the male reproductive system that creates pollen—the male sex
cells of plants.
The filament holds up the anther so that the pollen made on the anther has
a better chance of being picked up by birds, bees, or even wind to fertilize
a plant.
Physical Science
We studied why things move the way they do. First, we described motion with Newton’s
three laws. Then, we measured the motion of a moving object using speed and velocity.
We can use the mathematical equation for work to describe how much energy it takes to
make an object move. The six simple machines can help transfer that energy to make
moving an object easier. Finally, we discussed how energy moves through particles as
waves.
Laws of Motion
Isaac Newton systematically described the physical laws that govern an object’s motion.
It might sound complex, but he broke it down into three simple ideas.
Law 1 (Inertia)—Objects at rest will stay at rest until an unbalanced force makes
the move. Likewise, objects in motion will remain in motion (at the same
velocity) until an unbalanced force changes that motion.
Law 2 (Acceleration)—We can measure how much force it takes to make an
object move (its acceleration, or change in motion) by dividing the force applied
to the object by its mass.
Law 3 (equal and opposite)—Forces act in equal and opposite pairs; for every
action, there is an equal and opposite reaction.
Speed and Velocity
Speed and velocity are related; speed describes how the distance an object travels in a
certain amount of time, and velocity measures the same idea but in a specific direction.
Speed, or the rate of movement, can be measured with the equation:
For instance, if I wanted to know the speed of a car that drives 150 miles in three
hours, I would divide the distance (150) by the time (3). The speed of the car is
50, and I use the units the example gives me to finish the answer: 50 miles per
hour.
Measuring velocity would give me the same answer, but I would also know the
direction the car is moving—50 miles per hour west.
Work
Work is another measure to describe the motion of an object. Using the example above,
the work equation would reveal how much energy it takes to move the car for 150 miles.
To measure work, multiply the force that was applied to the object by the distance
it traveled.
Notice how the direction of the force and the direction of the object’s movement
(the distance) are the same.
To find out how much work it takes to move the car 150 miles, we need to know
the weight of the car. That may seem strange, since the equation above wants the
force you apply to it. It relates to Newton’s first and second laws of motion. If I
want the object at rest to move, I have to apply a force. The law of acceleration
tells me how much force I need to apply to make the car move. Weight is simply
a measure of how much gravity is pulling the object down. So, we’ll say the car
weighs about 3,000 pounds. 3,000 pounds is equivalent to about 13,000 Newtons
of force. So, to find out how much energy it takes to move the car:
Work (joules) = Force x Distance
? = 13,000N x 150 miles
=1,950,000 joules of work
(Yes, that much! Cars are heavy and 150 miles is a long way!)
Simple Machines
The six simple machines can help make work easier. We used the mnemonic Weird
People Sit With Large Iguanas to help us remember the six simple machines:
Wedge, pulley, screw, wheel and axle, lever, and inclined plane.
How do machines make work easier? They change the direction or size of the force
necessary to make the object move.
Direction
Size
Notice that in the example to the right, the force (effort) has to travel a longer
distance. Mathematically, if the distance increases, then the force must decrease.
The amount of work, or energy, it takes to move an object a certain distance is
ALWAYS the same.
So, if it took 100 joules of work to move this box (50N) two meters
without the lever, it would take less force but over a longer distance when
I do use the lever. The equation would change something like this:
WITHOUT the lever: 100j = 50N x 2m
WITH the lever: 100j = 25N x 4m
So, the force is applied over a longer distance, but that means it
takes less effort; the machine made work easier.
Waves
A wave is the movement of energy. We focused on two types of waves, or ways that
energy moves.
In a transverse wave, the energy moving causes the medium, or particles, to move
up and down. An example of a transverse wave would be how a guitar string
moves when you pluck it. They look like this:
In a longitudinal wave, the energy causes the particles to move back and forth.
Sound is the most common example of longitudinal waves.