Transcript Temperature (°C) - Rosshall Academy

National 5
Biology
Experimental
design,
presentation
and
interpretation
skills
Experiments
Every experiment needs:
• A control experiment.
• To be reliable.
• To be designed so that it is possible to
draw valid conclusions from a valid
experimental design.
• Well presented results and conclusions.
• Correct calculations
You can move to each section by clicking on the link
You can return here by clicking the symbol
The Control Experiment
A control experiment allows you to be
certain that the variable that you are
investigating is the variable that is
causing the effect.
What do you do?
• You do the experiment again.
• You leave out the variable that
you are investigating.
A Control Experiment examples:
• A scientist wants to know the effect of heat
on the enzyme pepsin.
• Pepsin will turn a cloudy solution of protein
clear as it digests the insoluble protein into
soluble peptides
• Test tubes of pepsin and protein are placed
in water baths at 10, 20, 30, 40 and 50ºC
• The time taken to clear is recorded
What is needed
for a control
experiment?
Do a second
experiment with boiled
*click*
(destroyed)
enzyme
?
A Control Experiment examples:
Investigating the
production of heat
from germinating
peas
Do a second
*click*
experiment
with boiled
(killed) peas
Investigating the
effect of acid rain on
the growth of
seedlings
Do a second
experiment using
distilled *click*
water instead
of the acid
?
?
Reliability
A reliable experiment is an experiment that
you can be sure will give you an repeatable
result every time you do it.
To ensure that you have not, by chance, got
a result from one of the extreme ends of the
normal range of variability.
What do you do?
Replicate (repeat) the experiment several
times and get an average of the results.
Valid Conclusions and Valid
Experimental Design
A valid experimental design is an experiment
where you control all the variables apart from
the one you are investigating.
If the design is valid then you are able to
draw valid conclusions.
Good Words and Bad Words
Some descriptive words linked to variables are
not acceptable
Bad words
Amount
Quantity
Size
Good words
Mass
Volume
Length
Width
Height
Volume
Warmth,
coldness,
heat, cold
Temperature
Acidity, alkalinity
pH
For example (1):
In an experiment to test the effect of
temperature on enzyme activity you must
control:
•pH
•The concentration of the enzyme
•The concentration of the substrate(s)
•The volume of the liquid
•The shapes of the containers
For example (2):
In an experiment to test the effect of light on
rate of photosynthesis you would need to
control:
•pH
•The temperature
•The concentration of Carbon dioxide
•The volume of the watering liquid
•The shapes of the containers
Results
Results can be presented as a table, as a
graph or both.
To draw a table.
•Lines are drawn with a ruler and surround
the table.
•There must be headings for each row or
column including SI units where
appropriate.
•There are no units in the body of the
table.
Temperature (°C)
Bubbles (number/s)
10
20
30
40
50
1
5
7
5
0
SI units
Do not use any other units or abbreviations
 1000
Type
Unit
x 1000
Length
metre (m)
kilometre millimetre
(km)
(mm)
Volume
litre (l)
kilolitre
(kl)
millilitre
(ml)
milligram
(mg)
other
micrometre
(µm)  1M
Temperature degrees
Celsius (ºC)
Mass
gram (g)
kilogram
(kg)
Energy
Joules (J)
kilojoules millijoules
(kJ)
(mJ)
Time
seconds (s)
tonnes
milliseconds minutes
(ms)
hours, days
For every experiment you need:
to know the input variable.
outcome variable
Experiments - Presentation
y
input variable
•The variable you change.
•This goes along the x-axis.
•This is the top row or first column in a table.
The outcome variable.
•The variable you measure.
•This goes along the y-axis.
•This is the bottom row or last column in a
table.
x
A Bar Chart –
Temperature (°C)
Bubbles (number/s)
separate bars
10
20
30
40
50
1
5
7
5
0
1.
Draw the axes
2.
Mark in the labels
3.
Mark the x scale
4.
Mark the y scale
6
5.
Draw the bars
5
6.
If you have time
shade in the bars
8
7
Bubbles
(number/s)
4
3
2
1
0
10
20
30
Temperature (°C)
40
50
A Histogram –
Temperature (°C)
Bubbles (number/s)
joined bars
10
20
30
40
50
1
5
7
5
0
1.
Draw the axes
2.
Mark in the labels
3.
Mark the x scale
4.
Mark the y scale
6
5.
Draw the bars
Bubbles
5
(number/s)
4
6.
If you have time
shade in the bars
8
7
3
2
1
0
10
20
30
40
Temperature (°C)
50
A Line graph
Temperature (°C)
Bubbles (number/s)
10
20
30
40
50
1
5
7
5
0
1.
Draw the axes
2.
Mark in the labels
3.
Mark the x scale
4.
Mark the y scale
6
5.
Draw the points
5
6.
Join the points
with straight lines
8
7
Bubbles
(number/s)
4
3
2
1
0
0
10
20
30
Temperature (°C)
40
50
A Pie Chart
Temperature (°C)
Bubbles (number/s)
10
20
30
40
50
3
6
12
3
0
3/24
6/24
12/24
3/24
0/24
⅛
¼
½
⅛
0
1.
Find the total
2.
Calculate the fractions
Fraction
Simplified fraction
3.
Draw a circle
4.
Mark off the
segments
5.
Make a key
Total
24
Temperature (°C)
10
20
30
40
50
Averages
Temperature (°C)
Bubbles (number/s)
10
20
30
40
50
4
8
14
4
0
To find the average number of bubbles …
1.
Find the total number of bubbles
2.
4 + 8 + 14 + 4 + 0 = 30
Divide the total by the number of items
There are 5 items in the table
30  5 = 6
3.
Don’t forget units in your answer
Average = 6 bubbles/s
Try this example …
Temperature (°C)
Bubbles (number/s)
Click here for answer
10
20
30
40
50
0
2
8
3
2
Percentages
Temperature (°C)
Bubbles (number/s)
10
20
30
40
50
4
8
14
4
2
To find the percentage of bubbles at 20ºC …
1.
Find the total number of bubbles
2.
4 + 8 + 14 + 4 + 2 = 32
Divide the number of bubbles at 20ºC by the total number
8  32 = 0.25 this is the decimal fraction
3.
Multiply the decimal fraction by 100 to get the percentage
0.25 x 100 = 25%
25% of the bubbles are produced at 20ºC
What percentage of bubbles are produced at 30ºC?
Ratios
Temperature (°C)
Bubbles (number/s)
10
20
30
40
50
4
8
14
4
2
To find the simple whole number ratio of bubbles at 10
degrees compared to bubbles at 20 degrees …
1.
Write down the ratio of the numbers
10ºC
4 bubbles
2.
:
:
20ºC
8 bubbles
Find a number that will divide into both numbers to give a whole
number – in this case 2
4 bubbles  2 : 8 bubbles  2
= 2 bubbles
:
4 bubbles
3. Repeat step 2 until you cannot divide again without getting a
fraction
2 bubbles  2 : 4 bubbles  2
= 1 bubble
:
2 bubbles
Ratios
Temperature (°C)
Bubbles (number/s)
10
20
30
40
50
4
8
14
4
2
To find the simple whole number ratio of bubbles at 20
degrees compared to bubbles at 30 degrees …
1.
Write down the ratio of the numbers
20ºC
8 bubbles
2.
:
30ºC
: 14 bubbles
Find a number that will divide into both numbers to give a whole
number – in this case 2
8 bubbles  2 : 14 bubbles  2
= 4 bubbles
:
7 bubbles
3. You cannot divide any more without getting a fraction so …
the simple whole number ratio is:
4
:
7
Percentage Increase
• To work out a percentage increase you can use
the following formula:
End value – Start Value
X 100
Start Value
• Example:
=
25
X
50 100
75 – 50
50
X 100
1
=
2
X
100
=50%
Percentage Decrease
• To work out a percentage increase you can use
the following formula:
Start value – End Value
X 100
Start Value
• Example:
=
25
X
50 100
50 – 25
50
X 100
1
=
2
X
100
=50%