Page 8 - 新思维科学学生用书6 样章
P. 8
Working like a scientist
• the water temperature is the independent
variable that we change
• the time it takes the solute to dissolve is the
dependent variable that we measure
• the amounts of water and solute and
number of times we stir the solution are the
control variables that we keep the same.
Observing over time
In investigations we often need to observe changes that are caused by the things we do.
How often we need to observe depends on the changes we are looking at. We can see
some changes straight away, such as the formation of a gas when we mix vinegar and
baking soda. If we observe what happens to our breathing rate when we exercise, we can
see the change in a few minutes. Observing changes in nature can often take longer. We
will need a month to observe the changes in the Moon’s appearance as it orbits the Earth.
first
quarter
waxing waxing
gibbous crescent
C
D B sunlight
Earth
full E A new
F H
waning G waning
gibbous crescent
third 7
quarter
