Transcript Scientific Method – Conducting an investigation

Why do we trust that Scientists
have correct explanations for
how “things” work?
 Scientist
use observations during an investigation to
gauge how the process is going but they also make
many observations to design their investigations.
 How do we make observations?
 Are some observations more important that others?
 Activity:

Candle Observations
On a piece of paper, you will make as many observations
has you can about the candles that I show you. You may
organize your paper how ever you would like.
 Observation
 Hypothesis
 Experiment
 Data
Collection
 Conclusion
 Retest
 Gathered
through
your senses
 A scientist notices
something in their
natural world
A
procedure
to test the
hypothesis.
Variable –
factor in the
experiment
that is being
tested
A good or
“valid”
experiment
will only have
ONE
variable!
An
experimenter
changes one
factor and
observes or
measures what
happens.
The
experimenter makes a
special effort to keep
other factors constant so
that they will not effect
the outcome.
 Those factors are called
control variables.
Controls
are NOT being
tested
Controls are used for
COMPARISON
The
factor that is changed
is known as the independent
variable.
The
factor that is measured or
observed is called the
dependent variable.
 For
example, suppose you want to figure out
the fastest route to walk home from school.
 You will try several different routes and time
how long it takes you to get home by each one.
 Since you are only interested in finding a route
that is fastest for you, you will do the walking
yourself.
Varying
the route is the
independent variable
The time it takes is the
dependent variable
Keeping the same walker
throughout makes the walker a
control variable.
Two
groups are required --the control & experimental
groups
There should be only one
variable
A
suggested solution to
the problem.
 Must be testable
 Sometimes written as
If…Then… statements
 Predicts an outcome
 An
example of a
hypothesis might be
that the salamanders
have curved tails due
to a pollutant in the
moist soil where they
live.
1.
2.
3.
Do not use I, me, my, they – no possessive pronouns.
If possible needs to be in a independent – dependent
variable format. (IF this happens, THEN this will
happen. )
It is a statement not a question.
Example:
If salt is added to fresh water, then the water will take
longer to freeze.
The If statement explains how the manipulated
variable is going to be changed.
The then statement explains how the responding
variable is affected by changing the
manipulated variable.
 If
the mass of a paper helicopter is
increased, then the time it takes to drop to
the ground will decrease.
 If fertilizer is given to a plant, then the
growth of the plant will increase.
 If a ball is hit with a wooden bat, then the
ball will travel farther than an aluminum
bat.






Hypothesis 1: If plants are given fertilizer, then the
height of the plant will change.
*In hypothesis 1 the then statement is not specific enough.
Hypothesis 2: If a plants height increases, then it was
because of the fertilizer.
* In hypothesis 2 the dependent variable was talked about
in the If statement and the independent variable was
talked about in the then statement.
Hypothesis 3: If the height of plant that is given fertilizer
increases, then it is because the fertilizer gave the plant
added nutrients.
* Hypothesis 3 has two problems. The first problem is like
hypothesis 2, the if and then statements are mixed up. The
second problem is this hypothesis does not give a prediction
for the scientific question stated above. It gives a
prediction on why fertilizers make plants grow more.
 Amy
wants to see how the amount of water in a pot
affects the time that it takes for water to reach
boiling point. She boils 100, 200, 300 ml of water.
The time it takes for the water to reach boiling
point increases as the amount of water increases.
 List the independent variable, dependent
variable, and the needed controls
 Construct a possible Hypothesis
 Independent:
Amount of Water
 Dependent: Boiling Time
 Controls: Type of water, heating apparatus
Constructing a Hypothesis:
If water amounts increase, then the time needed for
water to reach the boiling point will also increase.

A study was done to see if leaves added to soil had an
effect on tomato production. Tomato plants were grown
in four large tubs. Each tub had the same kind and
amount of soil. The 1st tub had 15 kg of rotted leaves
mixed in the soil and 2nd had 10 kg. The 3rd tub had 5 kg
and 4th tub had no leaves added. Each tub was kept in
the sun and watered the same amount. The number of
kilograms of tomatoes produced in each tub were
recorded
 What
is the independent variable? Dependent
variable?
 What are the controls?
 Write a possible hypothesis for this experiment.
 Independent
Variable: Music being played
 Dependent Variable: Growth of plant
 Hypothesis:



If music is played to plant over a period of time,
then the growth of the plant will increase.
If music is played to plant over a period of time,
then the growth of the plant will decrease.
If music is played to plant over a period of time,
then the growth of the plant will have no effect.
 Independent:
Amount of Leaves
 Dependent: Kilograms of tomatoes produced
 Controls: Soil type and amount, Sun and
water amount.
 Hypothesis:


The larger amount of leaves added to soil will
produce larger amounts of tomatoes.
It is hypothesized that changing the amount of
decomposing leaves in soil will not effect
tomato growth.
James wondered if music had an effect on plant
growth. He set up an experiment where 25 bean
plants were placed in a chamber where music was
played and 25 bean plants were placed in an
identical chamber where music was not played.
The growth chambers were kept at the same temp
and all plants received the same amount of
sunlight, fertilizer, and water. At the end of 2
weeks plant height was measured.
 What is the purpose?
 What is the independent variable? Dependent
variable?
 Write a possible hypothesis for this experiment.

Results
of the
experiment
May be
quantitative
(numbers) or
qualitative
Must
be
organized
Can be
organized into
charts, tables,
or graphs
 Qualitative
Data - describes the situation and
reaction in descriptive terms. For example,
qualitative involves the senses including sight,
taste, hearing, touch, and smell. This would
include color and shape
 Quantitative - includes those things that can
be measured (length, time, mass, temp. etc.)
 Qualitative vs. Quantitative Data http://www.regentsprep.org/Regents/math/A
LGEBRA/AD1/qualquant.htm
 http://regentsprep.org/regents/math/algebra
/ad1/dataprac.htm
A
well-designed investigation must have
some type of MEASUREABLE data,
quantitative, but qualitative gives the
measurable data more description and
accuracy.
 Scientist use qualitative data to record
observations that are difficult to measure or
to give clarification to measured data.
The
answer to
the hypothesis
based on the
data obtained
from the
experiment
In order to
verify the
results,
experiments
must be
retested.
1)Identify a Problem
2) State Observations about
the problem
3) Form a Hypothesis about the
problem (if…then…)
4) Design an Experiment to test
the hypothesis
5) Collect Data
6) Form a Conclusion
7) Retest


A team of scientists wonder if the amount of Vitamin A
given to laboratory white mice would affect the number
of offspring born. An experiment is set up using the
same species of white mice. Each mouse in the study
gets the same amount of food, daily exercise, and is
kept at the same temperature. Once group of mice gets
extra vitamin A supplements added to their food. The
number of offspring are counted and recorded.
Which of the following is the best Hypothesis – Explain why the wrong
ones are incorrect.
1.
2.
3.
4.
Mice will have more offspring if they are given Vitamin A.
If the mice are exposed to Vitamin A, then the amount of
offspring will increase.
If you give mice Vitamin A, then they will have more
offspring
I think the offspring number will increase if the mice are
exposed to Vitamin A.
A
scientist wonders how acid might effect
salamander’s hatching and growth. A scientist places
100 salamander eggs (Group X) in a pond that is
exposed to acid rain. He places another 100 eggs
(Group Y) in a pond where acid rain has not been
detected. The conditions such as temperature,
mineral content of the water, amount of sunlight
are as similar as possible in both areas.
1. Determine Independent Variable? (2pts each)
2. What are some possible Dependent variables?
3. Construct an Hypothesis for this experiment.
Candy wondered if caffeine would affect the
breathing rate of goldfish. She went to the store and
purchased 10 goldfish of approximately the same age
and size, identical containers, food, and caffeine
tablets. In one container she placed 5 goldfish with
no caffeine. In the other container she placed 5
goldfish with caffeine tablets dissolved in the water.
She observed the goldfish behavior and counted the
operculum (plate that covers gills) movements in
both containers of fish.
1. Determine Independent Variable?
2. What are some possible Dependent variables?
3. Construct an Hypothesis for this experiment.

 English
System – we’re the only industrialized
nation that uses this system as it’s standard
measurement. (pounds, ounces/cups, miles,
Fahrenheit, etc.)
 History – was based off of body parts and
commonly used objects.
 Drawbacks: complex converting and same
names for different measurements such as
ounce for both weight and liquid capacity.
 Metric
(International System of Units SI)
universally used in scientific work, and widely
used around the world for personal and
commercial purposes.
 A standard set of prefixes in powers of ten
may be used to derive larger and smaller
units from the base units.
 Mass
– unit is grams (g), used for measure
how much matter makes up an object.
Tools used: triple beam balance, digital balance
 Unit
– liter (L) (in
class use mainly
mL)
 Used to measure
how much space a
liquid takes up.
 Tools: graduated
cylinders (most
accurate), beakers,
Flasks
 Solid
Volume – cm3
or m3is the unit,
used for measuring
the amount of space
an object takes up.
To find the volume of
a solid measure the
length, width, and
height. Multiply all 3
numbers together.
 Measuring Irregular
solids – use the water
displacement method
but you will still
record the volume
using cm3
 Ruler, graduated
cylinder and water

 Unit
– meters (m)
 Used for measuring the distance between
two points.
 Tools - rulers
 Unit
– Celsius, C
 Used to measure the movement of molecules
in a substance. The more movement the
higher the temperature.
 Tool: Thermometer
 Celsius is based on the freezing and boiling
point of water. 0 degrees for freezing and
100 degrees for boiling.
 Fahrenheit is less accurate.
1.
2.
3.
4.
5.
6.
How much matter in a calculator?
How much space dr. pepper takes up in
your drinking cup?
How much space a textbook takes up in
your book bag?
The distance from Main Hall to Math Hall?
How much space a paper clip takes up?
The height of your desk?
1.
How much matter in a calculator?
use a balance and measure in grams
2.
How much space dr. pepper takes up in your
drinking cup?
use a graduated cylinder and measure in milliliters
(mL)
3.
How much space a textbook takes up in your
book bag?
use a ruler, LxWxH, unit cm3
4.
The distance from Main Hall to Math Hall?
ruler, meters
5.
How much space a paper clip takes up?
water displacement method, cm3
6.
The height of the your desk?
ruler, centimeters (cm)
 The
amount of matter in a given volume
 Mass (g)/ volume (mL3) = Density (g/mL3)
 Practice Problems:
1.
You have a rock with a volume of 15cm3 and a
mass of 45 g. What is its density?
2.
You have a different rock with a volume of
30cm3 and a mass of 60g. What is its density?
3.
Which rock is heavier? Which rock is more
dense?
A
golden-colored cube is handed to you. The
person wants you to buy it for $100, saying
that is a gold nugget. You pull out your old
geology text and look up gold in the mineral
table, and read that its density is 19.3
g/cm3. You measure the cube and find that it
is 2 cm on each side, and weighs 40 g. What
is its density? Is it gold? Should you buy it?