Measuring the Rate of Diffusion of Hydrochloric Acid (HCl)

through Agar Gel of different sizes

1 A Block10mm x 10mm x 10mm

Cut to produce 2 B Blocks

10mm x 5mm x 10mm

Cut to produce 4 C Blocks

10mm x 5mm x 5mm

Cut to produce 8 D Blocks

5mm x 5mm x 5mm

This diagram is on page 14 of your Handbook:

First cut 4 Agar Blocks dimensions: 10mm tall x 10mm wide x 10mm deep

1 A Block 2 B Blocks 4 C Blocks 8 D Blocks

10cm3 diluted HCl

Delay of 1 minute

Delay of 1 minute

Delay of 1 minute

START TIME 0s

Block Type A B C DStart 0min 1min 2min 3min

Finish __min__s __min__s __min__s __min__s

Total time Taken for block to change colour completely / S

sec sec sec sec

Rough work:

HCl (Acid)

SAFETYGoggles and lab coats on until I say to remove them. Long hair tied back. All bags and coats tucked under desks.

Hydrochloric Acid (HCl) and Ammonium Hydroxide (Alkali) and Creosol red dye

IRRITANTS-wash skin immediately if spillage occurs and report it to me.

Knife / Scalpel SHARP -Take care

TASKS TO DO:1.Write your group’s results onto the board.2.Copy all of the class data onto the table on p15 Handbook.3.Complete the table of calculations on p15 HB ASK FOR HELP IF YOU HAVE ANY DIFFICULTIES.4.Do the tasks found at the end of p15 HB ie GRAPH, WRITE A CONCLUSION, DESCRIBE ANY LIMITATIONS IN THIS EXPERIMENT.5. Print out the summary notes found on slides 7 and 8 from: MOODLE, Biology AS, UNIT 2, ‘Cells and Systems’, ‘Differentiation and Transport Systems’, ‘2. Surface Area to Volume ratio ppt’, just print out slides 7 & 8 only. FINISH FOR HW READY FOR NEXT LESSON.EXTENSION: Collect exam questions sheet from me and try to write answers to some of the questions on file Paper.

X

y

Surface Area / Volume RatioExpressed as a single value to 1dp.

Averagetimetaken foracid todiffuseintogel / s

= 1200= 1000= 800= 600

1000100010001000

1200:10001.2

1000:10001.0

800:10000.8

600:10000.6

6 sides of 5x5So 150mm2 per block.There are 8 blocks so:

(4 sides 10x5) + (2 sides 5x5)ie 200+50=250mm2 per blockThere are 4 blocks so:

(2 sides 10x10) + (4 sides 10x5) ie 200+200 = 400mm2 per blockThere are 2 blocks so:

6 sides of 10x10, = 6 sides of 100mm2

8 blocks4 blocks2 blocks1 block

5 x 5 x 55 x 5 x 1010 x 10 x 510 x 10 x 10

Total Volume / mm3

Surface Area/VolumeRatioAs a single value 1dp

Total Surface Area / mm2

Number of blocks of this type immersed in HCl (acid)

Dimensions of one block / mm

DCBABlock

Table to show the Relationship between Surface Area : Volume Ratio and Diffusion Rate

Block A B C D

Dimensions of one block / mm 10 x 10 x 10 10 x 10 x 5 5 x 5 x 10 5 x 5 x 5

Number of blocks of this type immersed in HCl (acid) 1 block 2 blocks 4 blocks 8 blocks

Total Volume / mm3

1000 1000 1000 1000

Total Surface Area / mm2600 800 1000 1200

Surface Area/VolumeRatio as a single value 0.6 0.8 1.0 1.2

Time Taken for blocks to all completely change colour /Seconds

Average time for diffusion (in seconds)

257 111 81 53

Table to show the Relationship between Surface Area : Volume Ratio and Diffusion Rate

Already Recorded times 257 111 81 53

X

y

Surface Area / Volume RatioExpressed as a single value to 1dp.

Averagetimetaken foracid todiffuseintogel / s

Graph to show………………………….....

X

y

Surface Area / Volume RatioExpressed as a single value to 1dp.

Averagetimetaken foracid todiffuseintogel / s

Graph to show the Relationship between the Surface Area : Volume Ratio and the Average Time for Diffusion

In this experiment the different sized jelly blocks were representing animals of different sizes with different surface areas:volume ratios.

WHAT ARE THE LIMITATIONS IN THIS INVESTIGATION?

END.

As x increases y increases at a GREATER rate

Interpreting Graphs

x

y1. 2.

x

y

As x increases y increases at a SMALLER rate

x

y

100

50

10 20

As x increases y increases at a steady rate. If x is doubled, y is doubled. We say that y is proportional to x

x

y

20

10

2 4

As x increases y decreases. It might be that if x is doubled then y is halved – in which case.. Y is inversely proportional to x

3. 4.