Topic 1 Practicals Flashcards
Vitamin C practical: name the dependent variable
the volume of fruit juice used/ the vit. C concentration in fruit juice - read off the calibration curve
Vitamin C practical: name the dependent variables (organism)
- source of fruit
- type of fruit juice
- storage time/conditions of juice
- ripeness of fruits
Vitamin C practical: why is DCPIP used?
DCPIP is an indicator that when oxidised is blue but then as it is reduced turns pink then finishes as colourless when fully oxidised. vit. C will reduce DCPIP
Vitamin C practical: what is the technique used?
titration
Vitamin C practical: why should only pale fruit juices be used?
So that the colour change of DCPIP can be easily seen
Vitamin C practical: state and justify a suitable control
Distilled water/0% vitamin C solution, for comparison to prove that it is the electrons from the vitamin C that change DCPIP from oxidised to reduced
Vitamin C practical: explain how to construct a vitamin C calibration curve
Titrate 5 solutions of known vitamin C concentration into a known volume of DCPIP and record the volume of vitamin
Vitamin C practical: state the purpose of the calibration curve
to find the vit. C concentration
Vitamin C practical: state the environmental controlled variables
Temperature
Vitamin C practical: state the procedural controlled variables
- volume of DCPIP
- conc. of DCPIP
- conc. of juice
Vitamin C practical: How many repeats should be carried out for each juice?
minimum of 5
Why are repeats necessary?
- recognise and remove anomalies
- calculate mean
- increase reliability and validity
Vitamin C practical: state the safety hazards and the precaution taken to minimise each one
- DCPIP may damage eyes - wear safety goggles
- Glass may cut skin - take care with glassware
Explain how to calculate the mean average from 3 sets of date
add the data up and divide by 3
Daphnia practical: what is the dependent variable?
the heart rate of the daphnia
Daphnia practical: sat and justify a suitable control
the heart rate of a daphnia in natural water or pond water
for comparison to prove that change in heart rate was due to caffeine
Daphnia practical: how many different caffeine solutions should you use?
at least 5
Daphnia practical: how many times should you repeat for each caffeine conc.?
at least 5
Daphnia practical: how should you aim to control temperature?
- turn microscope light off when not being used
- keep room temp. the same
- keep solutions at same temp. using a water bath
Daphnia practical: why are daphnia a good organism to use?
- they are transparent so the heart can be seen without dissection
- invertebrate, less ethical issues
Daphnia practical: why should you count the number of heart beats for 15s then x4, instead of for 60s
data is more reliable as high heart rate is difficult to count
Daphnia practical: what is the independent variable?
the caffeine concentration
Daphnia practical: state the controlled variables relating to the daphnia
- age
- gender
- size
- type/species
Daphnia practical: If the heart rate is measured, and values of 200, 204, 211, 199 and 197 are obtained, calculate the mean heart rate AND the range
mean: 202.2
range; 14
Daphnia practical: What is the ethical absolutism view about using Daphnia for this investigation?
under no circumstances should Daphnia be used in this investigation
Daphnia practical: What is the ethical relativism/utilitarianism view about using Daphnia for this investigation?
If the benefits outweigh the risk to the Daphnia, they should be used
Daphnia practical: How could you control the pH of the caffeine solution, to prove that this wasn’t affecting the heart rate?
Use a buffer and check the pH using a pH meter
Daphnia practical: Daphnia are found in nature in ponds. Suggest the optimum temperature for the enzymes inside Daphnia
between 5 and 10 *C
Daphnia practical: Define poikilotherms
effected by changes in environmental temperature
Daphnia practical: why do we use a cavity slide?
the depression in the slide helps the drops of solution stay on the slide
What are range bars
these show you the highest and the lowest values in a data set, on either side of the mean
What is standard deviation? (SD)
standard deviation is used to tell how far apart on average any point is from the mean
How should readings be recorded in a titration?
- from the bottom of the meniscus
- recorded to 2 d.p. ending in 0 or 5
