practical

Question 1

steps to light a bunsen burner

+ safety precautions!

Answer 1

• safety precautions: wear goggles, move chemicals, books and papers away
  1. close the air hole
  2. turn on the gas tap
  3. hold lighter to top of the barrel & click (if repeated attempts fail, TURN OFF THE GAS TAP)
  4. adjust flame size with gas tap
  5. adjust flame type by turning collar (non-luminous -> open the air hole)

turn the gas off if flame not needed

Question 2

how to calculate magnification?

Answer 2

• X size of drawing/size of actual specimen
• use dotted lines to extrapolate accurate length of drawing

X is the unit (multiplication symbol)

Question 3

biological drawing guidelines?

hint: SLAPTM

Answer 3

S: size should be 2/3 space
L: lines should be unbroken and continuous
A: accuracy of details & horizontal labelling
P: proportion accurate relative to the specimen
T: title
M: magnification

Question 4

pointers when drawing tables

think space, what to draw with etc.

Answer 4

1. draw the table lines in pencil. everything else is in pen.
2. headings should contain appropriate SI units (in case of quantitative data)
3. draw the table before beginning the experiment.
4. leave space to the right of the table in case more columns must be added.
5. table should occupy 2/3 of space.

Question 5

SOURCE OF ERROR: different tissues have different starting water potentials/concentration of x substance etc. –> inconsistencies in results.

suggest how to minimise/avoid this.

Answer 5

take samples from the same part of the fruit/vegetative organ etc. to ensure they have the same concentration/amt./water potential etc.

Question 6

SOURCE OF ERROR: determining colour change/intensity for experiment is subjective –> inaccurate results.

suggest how to minimise/avoid this.

Answer 6

compare reaction mixture against a colour standard/chart

Question 7

SOURCE OF ERROR: temperature of water bath was not kept constant –> could affect rate of reaction etc.

suggest how to minimise/avoid this.

Answer 7

use a thermostatically-controlled water bath
OR
use a thermometer to measure the temperature of the water bath & add hot or cold water to keep the temperature constant