Year 10 Practical Assessment Skills – Lesson 2 Conclusions

Aim: to be able to make conclusions by using results and graphs

Must: make simple conclusions using “er” statements

Should: be able to identify patterns in results

Could: identify errors in results and account for them, suggesting possible improvements

Say what you have found out Using “er” statements

• After completing an experiment it is important to say what you have found out.

• If possible it is best to use an ER statement.

• Change the following to an ER statement.

• A block of wood will burn quicker if it is cut up into small bits.

• The smaller the wood the quicker it burns

GCSE Biology Coursework Osmosis Practical Example

Background Science Osmosis is the diffusion of water molecules across a partially permeable membrane, from a region of high concentration to a region of low concentration. The partially permeable membrane contains a series of small holes, allowing only water molecules to pass through. For example glucose molecules are too big to fit through the membrane. As there are a greater number of water molecules on one side, there is a steady net flow into the other side with fewer water molecules, i.e. into the stronger solution

GCSE Biology Coursework Osmosis Practical Example

Factors which could have an affect on osmosis in plant cells. • Surface area of the potato plug – It may make the process of

osmosis slower, if a large potato plug is used in the experiment. • Sucrose concentration – Osmosis may be quicker if the

concentration is stronger. • Age of potato – Osmosis may be more efficient in newer potatoes

than older ones. • Variety of potato – Osmosis is likely to differ if a different variety of

potato cells are used. • Temperature – If the temperature is hotter, this may speed up the

process of osmosis. • Mass of the plug – Again, it may slow down osmosis if the potato

plug is many cells thick compared to only a few cells thick.

Osmosis Practical Results: Set 1

Sucrose Concentration

Mass Before (g)

Mass After (g)

Mass Change (g)

% Mass

Change

1M 2.19 1.91 ▼0.28 ▼12.79

0.8M 2.08 1.93 ▼0.15 ▼7.21

0.6M 1.90 1.81 ▼0.09 ▼4.74

0.4M 2.06 2.01 ▼0.05 ▼2.43

0.2M 2.21 2.18 ▼0.03 ▼1.36

0M 2.49 2.61 ▲0.12 ▲4.82

Osmosis Practical Results: Set 2

Sucrose Concentration

Mass Before (g)

Mass After (g)

Mass Change (g)

% Mass Change

1M 2.17 1.95 ▼0.22 ▼10.14

0.8M 2.30 2.16 ▼0.14 ▼6.09

0.6M 2.12 2.04 ▼0.08 ▼3.77

0.4M 1.99 1.96 ▼0.03 ▼1.51

0.2M 1.89 2.00 ▲0.11 ▲5.82

0M 2.18 2.41 ▲0.23 ▲10.55

Osmosis Practical Results: Set 3

Sucrose Concentration

Mass Before (g)

Mass After (g)

Mass Change (g)

% Mass

Change

1M 2.19 2.00 ▼0.19 ▼8.68

0.8M 2.18 2.06 ▼0.12 ▼5.50

0.6M 2.31 2.22 ▼0.09 ▼3.90

0.4M 1.99 1.95 ▼0.04 ▼2.01

0.2M 2.29 3.00 ▲0.01 ▲0.44

0M 2.16 2.41 ▲0.25 ▲11.57

Osmosis Practical Results: Averages

Sucrose Concentration

Average Mass Change (g)

Average % Mass Change

1M ▼0.23 ▼10.54

0.8M ▼0.14 ▼6.27

0.6M ▼0.09 ▼4.14

0.4M ▼0.04 ▼1.98

0.2M ▲0.03 ▲1.63

0M ▲0.20 ▲8.98

Graph Showing % Mass Change when Potato are placed in Sucrose Solution

Sucrose Concentration (M)

% M

ass

Ch

ange

GCSE Biology Coursework Osmosis Practical Example

TASK: From the information you have now be given on the osmosis practical write a conclusion for the experiment.

Help

• Remember you are trying to say what you have found out from the experiment or analysing the data.

• If possible it is best to use an ER statement.

Key “er” Words (examples);

“bigger”; smaller; “faster”; “slower”; “heavier”; “lighter”

Other Practical Examples

On the following slides try to make a conclusion and if possible identify any errors in the data.

Rolling a car down a ramp and measuring speed at a fixed point.

Height of ramp (cm) Speed (m/s)

5 1.2

10 1.5

15 0.7

20 2.1

25 2.4

30 2.7

35 3.0

40 3.3

• How can the data be made more reliable? • Are there any anomalies? • What variables need to be controlled?

Speeds reached

0

0.5

1

1.5

2

2.5

3

3.5

5 cm

10cm

15cm

20cm

25cm

30cm

35cm

40cm

• How can the results be showed more clearly? • What other improvements are needed?

Conclusion

• “The speed of the car always increases if the ramp is made higher”

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Examples of conclusions

• Example 1

My results show me that some rocks fizz and some do not when acid is added.

Hydrochloric acid made calcium carbonate fizz, sulphuric acid made sodium carbonate fizz and copper carbonate made hydrochloric acid fizz. Fizzing also happened between zinc carbonate and nitric acid and iron carbonate and hydrochloric acid. None of the other rocks fizzed. The reason for this is that there is a reaction between some types of minerals that might be in rocks and acids. You could use this as a test for some minerals, but you could not tell which is which. The bubbles mean that a gas is made in the reaction. The gases I know about are hydrogen, oxygen and carbon dioxide, it could be one of these, but I would need to test them.

Examples of conclusions • Example 2

My results show me that fizzing only occurs with those minerals that contain carbonate. The results also show that it doesn’t matter what type of acid you use. I conclude that carbonates react with acids to produce a fizz. You could use acids to test whether rocks contain carbonates or not.

The fizz means that a gas is given off. This gas is probably carbon dioxide, because it comes from a carbonate and the names are similar. I could test and be sure by seeing if the gas turns limewater milky.

To be completed

Conclusion 1 Strengths Conclusion 1 Weaknesses

Conclusion 2 Strengths Conclusion 2 Weaknesses