2C
BIO
If 10 meters of wire
needs 50 volts to
maintain 1.5 amps,
8 x 10 = 80m of
wire
and 8 x 50 = 400 volts
The graph shows how the voltage needed to maintain a
constant current of 1.5 amps through a wire conductor varies
with the length of the wire. If the trend continues, what is the
most likely voltage needed to maintain a 1.5-amp current
through 80 meters of the wire?
A
B
C
D
10 volts
18 volts
250 volts
400 volts
D 11/06
2C
BIO
B
11/05
A researcher determined the percentage of electrical energy
transformed into different forms of energy by a toaster. The
best way to communicate these results is to display the data
using a ---
A
B
C
D
histogram
circle graph
line graph
box-whisker graph
Average Radius of Trees in a Forest
Age of trees
(years
Average Radius
(cm)
1
2.2
2
2.6
2C BIO
C
10/06
3
4
5
6
4.4
The data table shows how the thickness of tree trunks in a certain forest
is related to tree age. Use these data to plot points on a graph. Draw a
straight line to show a linear relationship for the data. According to these
data, what is the most likely average radius of 4-year-old trees in this
forest?
A. 3.0 cm
B. 3.3 cm
C. 3.6 cm
D. 3.9 cm
2C BIO
C
10-04
According to the graph,
about how much
hemoglobin would be
saturated at an O2 pressure
of 7.3 kPa?
A
B
C
D
32%
67%
89%
92%
On the TAKS test, you will be tested
over your knowledge of how to design
and carry out a scientific experiment.
So what are the steps in planning and
implementing a valid experiment?
Dictionary Help: VALID means
acceptable, or legitimate,
trustworthy.
Dictionary Help:
IMPLEMENTING means doing the
experiment, taking the steps to
make it happen.
Asking questions: Can you look at an experimental
set-up and figure out what question the scientist was
trying to answer? Look for clues in the drawing or
paragraph! What are they measuring? What does the
data tell you?
The diagram shows an experimental
setup. Which of these questions was
this experiment designed to answer?
A Does water boil when exposed to
air?
B Will fire turn a gas into a liquid?
C Does air expand when heated?
D Will heat turn a gas into a solid?
Heat
Formulating Testable Hypothesis
Can you recognize a valid hypothesis? Can you
create one?
Is it a statement that you can prove with data?
What question
Is it testable?
might these
students be trying
to answer?
What hypothesis
might these
students write to
test their question?
Is the experiment valid?
Factors affecting the validity (trustworthiness)
of the experiment
• A control group is used
• The hypothesis has measurable variables
(“Flowers grown indoors will have the ‘best’
smell,” is not a measurable variable!)
• Sample size is large enough. You have to
run lots of test over and over again to get
reliable results
• Only one variable is tested at a time! “Will
limiting sunlight and water effect plant
growth?” is not a valid question!
Your teacher has given you two unknown white solids.
Your task is to mass out a sample of each compound
for each test and determine the following:
Procedure
Equipment
Procedure
Equipment
Procedure
Equipment
1. Melting Point
2. Conductivity
of solution
3. Solubility
Variables
• The dependent variables (the ONES
THAT ARE CHANGING)
• The independent variables (the
MANIPULATOR – CAUSE THE
CHANGE)
The picture shows an experiment using
different colors of light with elodea
Wavelength (Color
of light)
plants.
Sunlight
Green
Red
Blue
Dependent variable: What is being
changed?
Question
answered in this
experiment:
Hypothesis:
Control Group:
Independent Variables: What is causing Controlled Variables:
the changed?
What is the
manipulator?
mL of Oxygen
Produced in 10
minutes
20
3
18
16
READ CAREFULLY!
30. The table shows the time it took trees of the same type and
size to drop all of their leaves after being grown in different
atmospheres. For the experiment to be valid, which of
these must be a constant for all the trees?
Dependent variable
F The height of all the trees during the entire experiment
All of the independent variables but one (gases added) must
remain constant for the experiment to be valid.
G The amount of water available to all trees during the experiment
Dependent variable
H The mass of fallen leaves collected from each tree
Dependent variable
J The rate of photosynthesis in all trees during the experiment
Selecting the correct procedure and equipment:
Sometimes you will be asked to select correct
equipment or the correct procedure from a particular
lab set-up.
Which procedure is best to use when determining the density of a rock?
F Place the rock in a water-filled beaker and find the height at which the rock
floats above the water.
G Use a ruler to measure the rock’s dimensions and then find its mass using an
analytical balance.
H Measure the mass of the rock on a balance and then find the volume of water
it displaces in a graduated cylinder.
J Place the rock in three liquids with different known densities and observe
which liquid the rock floats in.
Formula Chart to the
RESCUE!!!!