Density
3 marks · EasyA student wants to compare the density of water and cooking oil in the lab.
Describe how she could measure the volume of 100 g of cooking oil.
State why the measuring cylinder must be placed on a flat surface when finding the volume.
Explain why repeating the measurement several times and averaging is useful.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Pour the oil into a measuring cylinder and read the scale at eye level. · must show pour into cylinder, read scale at eye level
(b) So the reading is accurate and not slanted/parallax error is avoided. · must show accurate reading, parallax error
(c) It reduces errors and gives a more reliable average value. · must show reduces random error, more reliable/average
Must show: measuring volume with cylinder, flat surface for accuracy, repeat for reliability
Common mistakes: Ignore parallax; Only say reduces error, no detail
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Describes measuring volume using a measuring cylinder.
B2 (b) · 1 mark · States reason for placing the cylinder on a flat surface (accuracy or avoiding parallax error).
B3 (c) · 1 mark · Explains the use of repeats: to reduce random errors/more reliable result.
Worked solution
a) Pour the oil into a measuring cylinder and read the scale at eye level. b) To ensure the reading is not slanted and avoid parallax error. c) Repeating and averaging reduces errors and gives a more reliable value.