flash cards from booklet
what is the IV
what you are changing
what is the DV
what you are measuring
what is the CV
what is remaining constant
e.g. enzyme concentration
same potato seeds from same variety and age
how is temperature best controlled
in a thermostatically controlled water bath
how is pH best controlled
using a buffer (works by resisting change in pH)
why are repeats needed?
-allow for the mean and standard deviation to be calculated
- a mean is more reliable than an individual reading
-standard deviation allows the spread of data around the mean to be identified
-repeats help to identify anomalous results
what to do if we get anomalous results when doing the experiment
do it again
what does a control experiment show
it shows the IV is the actual cause of changes in the DV
what would you need to do if you were asked to design a control experiment
need to describe one that eliminated the effect of the IV.
the IV is inactivated, experiment otherwise identiacal
after doing a control experiment, what would no change in the DV mean
shows it’s the changes in the IV that generates the different variables
what must you state when describing a control experiment
‘all other variables remain the same and experiment is conducted in the same way’
example of a control experiment
(related to enzyme activity)
the control would be to boil the enzyme for 5 minuted to denature them and then allow them to cool, to prove that any changes are as a result of the enzymes. the same volume of enzymes should be used
what is the hazard
object/chemical
e.g. naked flames/sharp instruments
what is the risk
and example
action in the method that can create a risk from the hazard (VERB NEEDED)
e.g. I could spill acid on my skin whilst POURING the acid into the beaker
what is the control measure
wear gloves to protect your skin
how to improve the accuracy
e.g.
usually changing some measuring techniques
e.g. using a colorimeter is a more accurate way of identifying a colour change compared to the naked eye (as this is subjective)
how to improve the validity
improved by controlling variables
often temperature or pH
how to improve reliability
improved by repeating the experiment and calculating a mean
what does your table need?
-correct column headings
-appropriate units of headings
-columns for sufficient repeats
-appropriate recordings of readings (same number of decimal places)
where do you put the IV and DV in your table
IV on the left (what you’re changing)
DV across the top (what you’re measuring)
what do range bars do
gives a good indication as to the reliability of your data
what do you need to do if asked to identify a trend
quote figures
how to comment on the consistency
use range bars (shouldn’t overlap if data is reliable)
if they are small you have consistent data (repeatable and reliable)
if data is wide spread you have inconsistent/unreliable data (Results deviate from the mean)
what is needed in a valid conclusion
sum up all your results into one brief statement
state whether the hypothesis was correct or not
what can be done with a calibration curve
can test the unknown solution in the same way as the known concentrations
use of calibrating the microscope
to measure the size of a structure on a microscope
how to calculate the actual size of an image (magnification)
if you are given the magnification
-measure the length of the line in mm (image size)
- convert to micrometers (um)—-x1000
- divide the image size by the magnification to give actual size in micrometers
what can the scale bar be used for
to calculate both magnification and actual size
mm to cm
divide by 10
um to mm
divide by 1000
mm to um
x1000
nm to um
divide by 1000
what type of microscope has greater magnification and greater resolution
electron microscope
what is the purpose of staining a microscope slide
used to give more contrast between cell structures and making them easier to see
when to reject the null hypothesis
when the value for x2 is greater than the value for the critical value
