Science Viscosity

GCSE Science – Investigative Skills Assignment – Marking Guidelines Chemistry 1.2 – Viscosity of Oils For submission in May 2007 or May 2008
Please mark in red ink, and use one tick for one mark. Subtotals for each part of each question should be written in the right hand margin. Please add annotations where necessary to explain why marks have or have not been awarded. Enter the marks for Section 1 and Section 2 and the total mark on the front cover of the answer booklet. The teacher must sign and date the front cover of the ISA. The papers must be kept in a secure place and must not be returned to candidates. SECTION 1 1 One mark for independent variable eg (How the viscosity of an oil) changes / varies with temperature 2(a) Any one from: (depending on the method used) • • • • • (b) cup viscometer – size of cup / size of cup hole / volume of oil falling ball-bearing – size of ball-bearing / distance the ball bearing falls trapped air bubble – size/diameter of tube / size of bubble / distance the bubble rises angled tile – angle of tile/slide / number of drops / tile surface etc correct answer based on the method used 1 mark 1 mark 1 mark 1 mark

Affects the timing measurement Explanation of how it affects the timing measurement eg the larger the hole the shorter the time it takes to empty the cup

3

Suggestion Explanation eg Uses pipette / burette / syringe (to measure volume) Measures out / delivers volume of oil more precisely or Smaller holes / smaller ball bearings / bigger tile etc Changes to the apparatus result in longer times or Details of a more precise timing method Suitable explanation

1 mark 1 mark

4

A continuous variable ticked for changing temperature or A categoric variable if different oils have been tested

1 mark

5

Amplified correct statement Simple correct statement for 1 mark only or

eg the viscosity of an oil decreases with increasing temperature (or converse) eg the viscosity of an oil changes with temperature