Physical World
: How Does It Work: Eggtimer
Trend Task
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  Level: Year 4 and year 8
Approach: One to one
Focus: Explain the operation of measuring instrument and predict the effects of alterations of its components.
Resources: Household instrument: eggtimer.

Questions / instructions:
In this activity I want you to try to explain how a bit of equipment works.
Give the student the eggtimer.
First of all have a look at this.

mean score
1. What do people use this piece of equipment for?
not marked
If the student doesn't know, tell them it is used to show when a certain amount of time has passed.
2. What is this piece of equipment called?
30 (38)
55 (64)
If the student doesn't know tell them it is an eggtimer.
3. Can you explain how the eggtimer works ?
When you turn it over the sand runs
through, taking a fixed amount of time

clear and correct
18 (22)
41 (49)
limited understanding
63 (72)
53 (49)
4. What would happen if:
     • there was more sand?
longer time
65 (64)
87 (87)
     • there was a bigger hole in the middle?
shorter time
85 (93)
97 (97)
     • the sand had larger grains?
longer time
29 (25)
48 (41)
might not go through
64 (63)
58 (56)
     • the sand was damp?
stick together and not go through
76 (83)
86 (92)
5. How could you change the eggtimer to make the time longer?
more sand
59 (53)
77 (71)
smaller hole
18 (18)
42 (38)
larger grains
5 (5)
11 (11)
Students in 1999 appeared less familiar with this form of eggtimer than the 1995 students. There was, however, no clear difference between the two years in ability to understand the operation of the timer and implications of changes in its components. Year 8 students scored substantially higher than year 4 students on most questions.
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