Practical C4. RATE of OSMOSIS

Practical C4. RATE of OSMOSIS

Practical C4. RATE OF OSMOSIS

BACKGROUND

All living organisms consist of cells and all cells are surrounded by a membrane. One of the major functions of the membrane is to regulate the passage of materials into and out of the cell. These materials include dissolved gases, sugars, salts and water. Cell membranes are ‘partially-permeable’ or ‘semi-permeable’ which means that some substances can easily pass through them, whereas others cannot. Most materials move by simple diffusion from high concentration on one side of the membrane to a lower concentration on the other. Some substances may be actively transported, which requires the provision of energy.

Water is the most abundant and one of the most important substances in cells. The diffusion of water across a partially-permeable membrane is called osmosis.

Vegetables are storage organs of plants which consist of cells and the products of cells. The cells are surrounded by a cell wall and, inside that, a plasma membrane. Vegetable tissue provides an excellent model to assist the understanding of the structure and function of membranes.

Part A Validating the technique

MATERIALS REQUIRED (per group)

1 large fresh potatoknife

spoonpaper towelling

ruler100 mL 10% NaCl soln

100mL distilled water2 x 250 mL beakers

accurate triple arm or electronic balance

METHOD

  1. Read right through this method and prepare a suitable data table in the space provided on the next page to record the masses.
  2. Obtain a large fresh potato, peel it and use a ruler to measure and a knife to cut four 2cm x 2cm cubes, split them into 2 pairs and use a balance to determine the mass of the pairs as accurately as possible.
  3. Place one pair of the cubes in one of the beakers and add the 10% salt solution so that the cubes are fully covered and leave it for 20 minutes, remove excess water and weigh and record the mass again. Calculate the change in mass and calculate % loss or gain and also enter this in the table. Also record any other observations.
  4. Place the other two cubes in the other beaker and cover them with distilled water and leave it for 20 minutes, remove excess water and weigh and record the mass again. Calculate the change in mass and calculate % loss or gain and also enter this in the table. Also record any other observations.
  5. When you have finished with your potato cubes please dispose of them as instructed.

RESULTS

In this space construct a table to record your measurements, possibly draw a graph and note any difficulties you encountered with the materials or techniques and how you will resolve them in Part B.

Part B ‘Design your own’ Practical

At the discretion of your teacher you may now be required to use the technique and knowledge from Part A to Design, Conduct and Report on your own practical investigation of this or another factor that may affect diffusion in agar or osmosis in potatoes.

You will need to:

  • prepare an Abstract after you have finished your experiment
  • write an Introduction
  • List the Materials you will need and explain the Method you will use
  • Record your Results in whatever form(s) you think appropriate
  • Write a Discussion of your method and results
  • State a Conclusion about the validity or otherwise of your hypothesis

You may refer to the Assessment Table on the last page for more detail about the relevant Intended Student Learnings and suggested marks for each of these headings.

C4 - Student Performance against the Assessment Design Criteriaand Performance Standards

Name of student Class

Specific features / Comment/evidence with regard to meeting Performance Standards / Grade
Investigation / I1Design of biological investigations.
I3Manipulation of apparatus and technological tools to implement safe and ethical investigation procedures.
I4The obtaining, recording, and display of findings of investigations using appropriate conventions and formats.
Analysis and Evaluation / AE1Analysis of data and concepts and their connections, to formulate conclusions and make relevant predictions.
AE2Evaluation of procedures, with suggestions for improvement.
Application / A2Use of appropriate biological terms, conventions, formulae, and equations.
A3Demonstration of skills in individual and collaborative work.
Knowledge Understanding / KU1Demonstration of knowledge and understanding of biological concepts.
KU3Communication of knowledge and understanding of biology in different formats
© S.T.A.R. 2014. Unauthorized copying prohibited.

Other comments:

______

C4 - Student achievement against specific Report headings

A.
D.
C. / Report headings and Intended Student Learnings
In their laboratory work and their written report, students should provide evidence of how well they have achieved the following student learnings:
KU3 / Abstract
  • Write a (concise) report of an investigation that includes a description of its purpose and procedure, results, analysis, interpretation, and conclusions.

I1 / Introduction
  • State the purpose of the investigation or experiment.
  • State the key ideas or background biology
  • State a testable hypothesis
  • Formulate a question for an investigation
  • Suggest possible investigations to test the question

I1
I3,4 / Materials and Methods
  • Identify and classify variables (independent and dependent)
  • Identify any factors that are deliberately held constant
  • Design and carry out investigations or experiments
  • Describe the steps of an investigation or procedure
  • Draw or interpret diagrams of the apparatus
  • Collect data using measurements that can be reproduced consistently.
  • Select an instrument of appropriate resolution

I4 / Results
  • Record and analyse observations
  • Use measurements to an appropriate number of significant figures
  • Distinguish between quantitative and qualitative evidence.
  • record careful and honest observations
  • use a table to present data
  • Plot a graph of dependent variable versus independent variable
  • Draw a line of best fit through a series of points on a graph

AE1
AE2 / Discussion
  • Identify sources of errors and uncertainty
  • Distinguish between random and systematic errors
  • Explain the importance of increasing the number of samples
  • Explain the importance of repeating a practical investigation
  • Determine which of two or more sets of measurements is most reliable
  • Use averages or graphing as a means of detecting or minimising random errors.
  • State which result of two or more experiments is most accurate
  • Describe a pattern observed in the results
  • Using the scatter in the graphs to compare the random errors.
  • Analyse and evaluate information, interpret results and suggest improvements

AE1 / Conclusion
  • Write a conclusion that is based on the results of an investigation

A2
A3 / Application skills
  • Use biological terminology, conventions, and symbols
  • Use concise language and graphics to present information.
  • Work ethically with animals
  • Report accurately and honestly
  • Recognise hazards and work safely
  • Demonstrate initiative and focused work skills
  • Negotiate procedures with the other members of the team
  • Perform the role of a team member.

KU1
KU3 / Communication
  • Demonstrate knowledge and understanding of biological concepts
  • Communication of knowledge and understanding of biology

© S.T.A.R. 2014. Unauthorized copying prohibited.

Name of studentClass Practical Date

Investigation / Analysis and Evaluation / Application / Knowledge and Understanding
A / Designs a logical, coherent, and detailed biological investigation.
Critically and logically selects and consistently and appropriately acknowledges information about biology and issues in biology from a range of sources.
Manipulates apparatus and technological tools carefully and highly effectively to implement well-organised safe and ethical investigation procedures.
Obtains, records, and displays findings of investigations using appropriate conventions and formats accurately and highly effectively. / Critically and systematically analyses data and their connections with concepts, to formulate logical and perceptive conclusions and make relevant predictions.
Critically and logically evaluates procedures and suggests a range of appropriate improvements. / Applies biological concepts and evidence from investigations to suggest solutions to complex problems in new and familiar contexts.
Uses appropriate biological terms, conventions, formulae, and equations highly effectively.
Demonstrates initiative in applying constructive and focused individual and collaborative work skills. / Consistently demonstrates a deep and broad knowledge and understanding of a range of biological concepts.
Uses knowledge of biology perceptively and logically to understand and explain social or environmental issues.
Uses a variety of formats to communicate knowledge and understanding of biology coherently and highly effectively.
B / Designs a well-considered and clear biological investigation.
Logically selects and appropriately acknowledges information about biology and issues in biology from different sources.
Manipulates apparatus and technological tools carefully and mostly effectively to implement organised safe and ethical investigation procedures.
Obtains, records, and displays findings of investigations using appropriate conventions and formats mostly accurately and effectively. / Uses clear and well-organised analytical skills to examine connections between data, concepts, and issues in biology.
Evaluates procedures and suggests some appropriate improvements.
Uses mostly logical analysis and evaluation of data and other evidence to formulate consistent and relevant conclusions. / Applies biological concepts and evidence from investigations to suggest solutions to problems in new and familiar contexts.
Uses appropriate biological terms, conventions, formulae, and equations effectively.
Applies mostly constructive and focused individual and collaborative work skills. / Demonstrates some depth and breadth of knowledge and understanding of a range of biological concepts.
Uses knowledge of biology logically to understand and explain social or environmental issues.
Uses a variety of formats to communicate knowledge and understanding of biology coherently and effectively.
C / Designs a considered and generally clear biological investigation.
Selects with some focus, and mostly appropriately acknowledges, information about biology and issues in biology from different sources.
Manipulates apparatus and technological tools generally carefully and effectively to implement safe and ethical investigation procedures.
Obtains, records, and displays findings of investigations using generally appropriate conventions and formats with some errors but generally accurately and effectively. / Uses generally organised analytical skills to examine connections between data, concepts, and issues in biology.
Evaluates some procedures in biology and suggests some improvements that are generally appropriate.
Analyses and evaluates data and other evidence to formulate simple and generally relevant conclusions. / Applies biological concepts and evidence from investigations to suggest some solutions to basic problems in new or familiar contexts.
Uses generally appropriate biological terms, conventions, formulae, and equations with some general effectiveness.
Applies generally constructive individual and collaborative work skills. / Demonstrates knowledge and understanding of a general range of biological concepts.
Uses knowledge of biology with some logic to understand and explain one or more social or environmental issues.
Uses different formats to communicate knowledge and understanding of biology with some general effectiveness.
D / Prepares the outline of a biological investigation.
Selects and may partly acknowledge one or more sources of information about biology or an issue in biology.
Uses apparatus and technological tools with inconsistent care and effectiveness and attempts to implement safe and ethical investigation procedures.
Obtains, records, and displays findings of investigations using conventions and formats inconsistently, with occasional accuracy and effectiveness. / Describes basic connections between some data, concepts, and issues in biology.
For some procedures, identifies improvements that may be made.
Attempts to extract meaning from data and other observations and to formulate a simple conclusion that may be relevant. / Applies some evidence to describe some basic problems and identify one or more simple solutions, in familiar contexts.
Attempts to use some biological terms, conventions, formulae, and equations that may be appropriate.
Attempts individual work inconsistently, and contributes superficially to aspects of collaborative work. / Demonstrates some basic knowledge and partial understanding of biological concepts.
Identifies and explains some biological information that is relevant to one or more social or environmental issues.
Communicates basic information to others using one or more formats.
E / Identifies a simple procedure for a biological investigation.
Identifies a source of information about biology or an issue in biology.
Attempts to use apparatus and technological tools with limited effectiveness or attention to safe or ethical investigation procedures.
Attempts to record and display some descriptive information about an investigation, with limited accuracy or effectiveness. / Acknowledges that connections exist between data, concepts, and/or issues in biology.
Acknowledges the need for improvements in one or more procedures.
Attempts to organise some limited data or observations. / Identifies a basic problem and attempts to identify a solution in a familiar context.
Uses some biological terms or formulae.
Shows emerging skills in individual and collaborative work. / Demonstrates some limited recognition and awareness of biological concepts.
Shows an emerging understanding that some biological information is relevant to social or environmental issues.
Attempts to communicate information about biology.
Performance standards (© SACE Board 2011)
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