Transcript Physics practical work

Physics
investigations
Learning outcomes

analyse roles and effectiveness of practical activities in science

consider how to mitigate the damaging effect of assessed practicals

discuss the design and evaluation of standard experiments suitable for
GCSE students

develop a repertoire of physics questions suitable for open-ended
investigations

discuss collecting and recording data, ways of improving the quality of
data

master a variety of simple measurement techniques used in physics

use a straight line graph through the origin as a test for direct
proportionality
Defining ‘practical work’
‘Any teaching and learning activity which involves, at
some point, the pupils in observing or manipulating real
objects and materials.’
Practical work
Very diverse in nature and purpose
Primary learning objectives:
• developing knowledge and understanding of the natural world
• practical capability - using scientific equipment or following
standard procedures
• developing understanding of a scientific approach to enquiry
Scientific enquiry
The quality of evidence is always of concern.
When planning and carrying out practical investigations,
pupils need to ask, for example,
• Is my method valid?
• Can I rely on my data when drawing a conclusion?
• Are uncertainties in the measurements small enough?
• Does the difference between one measurement and another
reflect a real change in the thing being measured?
NASA Astronomy
Picture of the Day
February 7, 1998
COBE was launched in November 1989. By March 1991, the research team saw
this pattern emerge in their data, but they could not be sure what was noise and
what was real. Possible sources of systematic error were rigorously identified,
checked and cross-checked. Only in April 1992 were the team ready to go public.
Instruments used in physics
• micrometer screw gauge – readings on sleeve (0.5 mm
graduations) & thimble (2 x 50): reads to 0.01 mm
• callipers – vernier scale divides 1 mm by 10: reads to 0.1 mm
VPL’s two simulations can be used for practice.
other instruments with
vernier scales
– travelling microscope
– spectrometer
Now try this
In pairs:
1 Use a micrometer to measure the diameter or
thickness of various objects.
2 Use vernier callipers to measure a variety of lengths.
Another learning objective
Communication skills
Pupils need to learn how to:
• analyse and present data;
• draw conclusions from data;
• evaluate the quality of data;
• present an account of a practical task.
Now try this
In groups of three:
Investigate the relationship between the distance a ‘hot
wheels’ toy car is drawn back and how far it then
travels forward.
Record and analyse any data that you collect.
‘The language of measurement’
Booklet from Nuffield-ASE
Aims:
to achieve a common understanding of important terms that arise
from practical work in secondary science e.g. ‘accuracy’ and
‘precision’
as used by professional scientists (agreed among international
metrology institutes - in the UK, National Physical Laboratory,
LGC)
Target audience: teachers, ITE and CPD providers, publishers,
awarding bodies.
Straight line graphs tell a story
direct proportionality
y  x or y  kx
e.g. I  constant  V 
V
R
linear relationship
y  mx  c where m  gradient, c  y intercept
e.g. gas pressure v temperature
Straight line graphs tell a story
periodic time, T, for a pendulum, length l
l
Replot to check that T  2
g
4
T 
 l  constant  l
g
2
2
Boyles’ law
Equation:
pV  nRT
nRT
p
V
Graph: Plot p against 1/V
(dependent against independent variable)
Straight line, passing through the origin with gradient =
nRT
Specific heat capacity
Equation:
Q  mcT
Q is found by using
energy = power x time
energy = current x voltage x
time
Equation:
IVt = mcDT
so
IVt æ IV ö
DT =
= ç ÷× t
mc è mc ø
Graph: Plot temperature change ∆T against time t
IV
Straight line, passing through the origin with gradient 
mc
So c 
IV
m  gradient
Now try this
In pairs:
What graph you would need to plot to confirm the
following relationships?
1 Seafloor spreading hypothesis: separation distance of
magnetic stripes, x, increases with age of seafloor, t.
2 Intensity of a light source: I 
k
x
2
I = intensity, x = detector distance from source, k = constant
Another set of learning objectives
Personal development
Practical work can help pupils to:
• become more motivated to study science
• become more confident and self-reliant
• learn something about working effectively with
others
More effective practical work
Characteristics:
•
the task has a limited number of intended learning
outcomes
•
the task design highlights the main objectives and
keeps ‘noise’ to the minimum
Two worlds
domain of real
objects and
observable
things
domain of ideas
More effective practical work (2)
•
Stimulate the pupils’ thinking beforehand, so that
the practical task answers a question which the
pupil is already thinking about.
•
If the task requires the pupils to make links
between the domain of objects and observables
and the domain of ideas, ensure that the structure
of the task ‘scaffolds’ their thinking.
Open-ended investigations
In pairs:
Discuss experiments listed on the handout ‘Ideas for
investigations at KS4’. Which of them might work with
your pupils? what year/class?
There is also a different list for A-level Physics.
Teaching challenges
Various factors constrain opportunities for student investigations.
• assessment requirements from some awarding bodies. e.g.
affects what teachers value; students can be tempted to copy
what others are doing, even when it is ill-advised.
• apparatus & technician support available can limit the variety of
approaches to investigating a similar question.
Conclusion: It may be best to encourage lots of simple, open-ended
investigative work at KS3, with the aim of developing practical
skills and encouraging scientific thinking – not assessment.
Further reading
Breithaupt opening chapter ‘Units and measurements’
Robin Millar (2010) Analysing Practical Science Activities
to assess and improve their effectiveness. ASE
Peter Campbell (ed.) (2010) The language of measurement:
terminology used in school science investigations.
ASE
extracts of both ASE booklets: www.gettingpractical.org.uk/Books.php