Lab Equipment, Procedures and Safety
Symbols
Use a graduated cylinder to accurately measure
liquids in milliliters (ml). You always
want to choose the graduated cylinder that holds the smallest amount possible
while not being smaller than the amount you are measuring-this allows it to be
the most accurate. When measuring, we
look at the bottom of the curve in the surface of the liquid (the meniscus). Beakers and Erlenmeyer flasks can be
used for storage and mixing, but are not as precise.
Use a triple-beam balance to measure mass in grams
(g).
Use a meter stick to measure length in meters (m)
or centimeters (cm).
Use a thermometer to measure temperature in
degrees Celsius (°C).
Use a spring scale to measure force in Newtons
(N).
Microscopes allow us to see object that are much
smaller than we can see with our eyes. When
carrying a microscope, carry it with one hand on the base and the other on the arm
of the microscope. To find the
magnification, multiple the magnification of the first lens by the
magnification of the second lens.
|
Light Microscope
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Electron Microscope
|
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Can view living
things
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Specimens must
be dead
|
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Can see color
and movement
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Black and white,
no movement
|
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Not very good
magnification
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Really good
magnification
|
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Easy to use, not
expensive
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Hard to use,
really expensive
|
Bunsen burners are used to heat up objects in the
lab. When using a Bunsen burner, make
sure that you keep your hair and cloths tied back so they don’t start on
fire. When heating a substance in a test
tube, make sure you don’t fill it all the way to the top and you point the top
of the test tube away from you so chemicals don’t splatter onto you. Also make sure nothing flammable is around
the flame.
The eye wash station is available to clean out
your eyes if chemicals get into them.
The safety shower is available if you get chemicals on your skin
or clothing. Make sure that you wear safely
goggles when working with chemicals to protect your eyes.
·
If you break glass, there is a special container
for broken glass-make sure you sweep it up and don’t touch it with your
hands-the edges are sharp and can cut you.
·
If a fire breaks out, use the fire extinguisher
and PASS (Pull the pin, Aim the nozzle, Squeeze the handles and Sweep the
nozzle side to side).
·
If you need to dispose of living tissues, use
the biohazard container.
·
If you ever find something that you can’t identify,
spill something, break something, or hurt yourself in any way, let the teacher
know!
Safety Symbols:
Radiation
Biohazard
Poisonous/Toxic
Flammable
Corrosive
No
food or drink
Hypothesis and Scientific Method
A
hypothesis is an educated prediction of what we think will happen. Hypotheses are often written as an If…then….
statement. If..then…statements always
make a prediction about what will happen if we change something. The most important thing to remember is that
a hypothesis needs to be something I can
test. Saying rap music is better
than pop music is not a hypothesis because we cannot test that. Saying more people prefer rap music in this
room than country music is a hypothesis because we can test that by taking a
poll.
The
scientific method is a systematic way to figure out the answer to a problem.
- Make
an observation or ask a question
- Gather
information
- Create
a hypothesis: an educated prediction of what is going to happen
- Design
and conduct an experiment
- Analyze
the data
- Draw
a conclusion
If
the data supports our hypothesis, then we can keep it and perform another
experiment to see if it still holds true.
If the data does not support our hypothesis, then we will reject the
hypothesis. If many experiments support
our hypothesis, then we call it a theory.
Theories have support from
many different experiments and many trials of each of those experiments. If something in science seems to always be
true, we call it a law.
Experiments
Experiments are how scientists determine relationships in
the world around them.
Independent
Variable: The variable that we change or vary to see what happens. If our hypothesis was an
if…then… statement, the IV would be the if.
Dependent
variable: The variable we measure to see what change has taken place. This will be the then of our
if..then…statement.
Constant: Something that does not change or remains the
same. Everything in an experiment other
than the independent variable should be constant.
Control is the group you are
going to compare everything to. It is the group where you don’t change
anything-it is the normal state of the IV.
Replicability: Doing an experiment multiple times to make
sure that you get the same results over and over
Common pitfalls of experiment designs:
·
Forgetting to have a control. A control is needed in order to tell if a
change has taken place. If you don’t
have a control, you don’t know if changing the IV has caused a change in the DV
(you have nothing to compare the experimental group to!).
·
Having
more than one IV. If we manipulate more
than one thing, it is impossible to know which manipulation caused the
differences we see in the DV. This is
why you only have one IV and everything else is kept constant.
·
Not
replicating the experiment. If you only
do it once, you cannot tell if that is the result you will always get. Replicability allows you to prove that this
will always happen. Part of replicability is having a large sample size when we
do experiments-if your sample is small, it is difficult to conclude that
something happens all the time.
Graphs
Parts of a graph:
Title-goes across the top. Tells you what the graph is about. Usually is
written to explain the variables you are comparing.
Axes
labels or legend- gives you information on what they represent and how they
are measured.
X-axis: the
horizontal one (side-to-side). Always
has the independent variable.
Y-axis: the vertical one (up and down). Always has the dependent variable.
Types of graphs:
Bar Graph: Used to compare data between groups.
Line
Graph: Used to compare data for an
independent variable that is continuous (can get larger and smaller like time
or temperature)
Pie Chart:
Used to show parts of a whole.
The information is given as percentages.
Creating Scales:
When you are deciding what value to make each division
along an axes, you need to take the largest value you have for each axes and
then divide that value by the number of divisions you have on that axes. You will then round up to the nearest value
that makes sense for the graphs (nearest whole number, nearest multiple of 5,
10, 100, ect.)
