J001- BIOLOGY FINAL PRACTICALS.
Photosynthesis practical - CORRECT ANSWERS-1. Place a boiling
tube 10cm away from an LED light source.
2. Fill boiling tube with sodium hydrogen carbonate solution. This
releases carbon dioxide which is needed for photosynthesis.
3. Place piece of pond weed into boiling tube with cut end at top.
Leave for 5 minutes to acclimatise to conditions in boiling tube.
4. Should see bubbles of gas from cut end. This is oxygen, produced
by photosynthesis.
5. Start stopwatch and count number of bubbles produced in one
minute.
6. Repeat twice and calculate mean number of bubbles produced in 1
minute.
7. Repeat whole experiment, but move boiling tube to a distance of
20cm, them 30cm, then 40cm.
Two problems with photosynthesis practical? Solution? - CORRECT
ANSWERS-Number of bubbles can be too fast to count accurately,
and bubbles are not always the same size.
Solution: measure volume of oxygen produced instead.
Place pondweed under a funnel and catch bubbles in a measuring
cylinder filed with water. Use measuring cylinder to measure volume
of oxygen gas produced.
Inverse square law for photosynthesis - CORRECT ANSWERS-Light
intensity= 1/distance squared
Double the distance, number of bubbles falls by a factor of 4 because
light intensity falls by 4.
Food tests practical - CORRECT ANSWERS-Simple sugars, such as
sucrose and glucose: blue Benedict's solution turns brick red on
heating if present.
Photosynthesis practical - CORRECT ANSWERS-1. Place a boiling
tube 10cm away from an LED light source.
2. Fill boiling tube with sodium hydrogen carbonate solution. This
releases carbon dioxide which is needed for photosynthesis.
3. Place piece of pond weed into boiling tube with cut end at top.
Leave for 5 minutes to acclimatise to conditions in boiling tube.
4. Should see bubbles of gas from cut end. This is oxygen, produced
by photosynthesis.
5. Start stopwatch and count number of bubbles produced in one
minute.
6. Repeat twice and calculate mean number of bubbles produced in 1
minute.
7. Repeat whole experiment, but move boiling tube to a distance of
20cm, them 30cm, then 40cm.
Two problems with photosynthesis practical? Solution? - CORRECT
ANSWERS-Number of bubbles can be too fast to count accurately,
and bubbles are not always the same size.
Solution: measure volume of oxygen produced instead.
Place pondweed under a funnel and catch bubbles in a measuring
cylinder filed with water. Use measuring cylinder to measure volume
of oxygen gas produced.
Inverse square law for photosynthesis - CORRECT ANSWERS-Light
intensity= 1/distance squared
Double the distance, number of bubbles falls by a factor of 4 because
light intensity falls by 4.
Food tests practical - CORRECT ANSWERS-Simple sugars, such as
sucrose and glucose: blue Benedict's solution turns brick red on
heating if present.
