Scientific Investigation

Science & Technology

Scientific Investigation 2

Scientific Investigation

Learning objectives: To identify the major steps in carrying

out a scientific investigation To acquire the skills in performing a

scientific investigation To collect, interpret, analyse and

evaluate scientific information

Scientific Investigation 3

Make Observations

Stretch a rubber band with both hands and record your observations.

Scientific Investigation 4

Make Observations

When you stretch the rubber band with greater force, the rubber band will become longer. That is, there is a direct relationship between the applied force and the extension of rubber band.

Scientific Investigation 5

Formulate a Hypothesis

Based on your observations, formulate a hypothesis relating the applied force with the extension of an elastic material such as rubber band, spring.

Scientific Investigation 6

Formulate a Hypothesis

The force exerted by a spring (an elastic material) is proportional to the distance the spring is stretched or compressed from its relaxed position.

F xF: applied force (e.g. weight ) x: extension of the spring

Scientific Investigation 7

Formulate a Hypothesis

x

unstretched spring

2x

F

2 F

F x

It takes twice as much force to stretch a spring twice as far.

Scientific Investigation 8

Test the Hypothesis

Materials provided: spiral spring with pointer stand with an adjustable mirrored

scale (15 cm) slotted weights (10 g, 20 g, 50 g)

Design an experiment to test the hypothesis.

Scientific Investigation 9

Test the Hypothesis Experimental design:

Perform several measurements to collect a set of data correlating the weights and the extension of spring

Plot a graph of weight vs. extension of spring to verify the formulated hypothesis

F xa plot of weight, F vs. extension, x should yield a straight line passing through the origin

Scientific Investigation 10

Discussion Questions for Lesson 1 of Chapter 2

What do you observe when stretching a rubber band with your hands?

Suggest some other scientific observations in your daily life.

What is a hypothesis? How would you formulate a

hypothesis?

Scientific Investigation 11

Suggested Answers for Questions (Lesson 1) What do you observe when stretching a

rubber band with your hands? When you stretch the rubber band with

greater force, the rubber band will become longer.

Suggest some other scientific observations in your daily life. Any free object will be falling downward due

to gravity A wooden block will float on water while a

metal block will sink

Scientific Investigation 12

Suggested Answers for Questions (Lesson 1)

What is a hypothesis? A tentative explanation of a scientific

question based on observations and past knowledge

How would you formulate a hypothesis? Formulating a hypothesis involves

inductive reasoning

Scientific Investigation 13

Test the Hypothesis (Suggested Procedure)

1.Set up the apparatus as shownin the figure.

Scientific Investigation 14

Test the Hypothesis (Suggested Procedure)

2.Record the starting position of the spring at its relaxed state as indicated by the marker.

3.Add 20 g slotted weight to extend spring to a measurable displacement (x). Record the weight and the length of spring to calculate the extension x.

Scientific Investigation 15

Test the Hypothesis (Suggested Procedure)

4.Repeat Step 3 for 4 more trials using different weight loads (e.g. 40 g, 60 g, 80 g, 100 g).

Scientific Investigation 16

Test the Hypothesis (Results)

Weight, F (g)

Length of spring (cm)

Extension of spring, x (cm)

0 0 0

20 1.0 1.0

40 2.0 2.0

60 3.0 3.0

80 4.0 4.0

100 5.0 5.0

Scientific Investigation 17

Test the Hypothesis (Results)

A Plot of Weight vs. Extension of Spring

0

20

40

60

80

100

120

0 1 2 3 4 5 6

Extension of Spring, x (cm)

We

igh

t, F

(g

)

Scientific Investigation 18

Draw Conclusion

Would you accept or reject the hypothesis? Why?

Scientific Investigation 19

Draw Conclusion

When the plotted graph is a straight line passing through the origin, there is a direct proportionality between the weight load (F) and the extension of a spring (x), i.e. F x. Hence, the hypothesis can be accepted.

If the plotted graph is not a straight line, the hypothesis should be rejected.

Scientific Investigation 20

Discussion Questions for Lesson 2 of Chapter 2

Describe briefly the steps required in order to test a hypothesis.

What is the purpose of drawing conclusion in a scientific investigation?

Scientific Investigation 21

Suggested Answersfor Questions (Lesson 2)

Describe briefly the steps required in order to test a hypothesis. Perform an experiment to collect,

interpret, analyse, and evaluate the data

Repeated experiments and control experiments are required

Scientific Investigation 22

Suggested Answersfor Questions (Lesson 2)

What is the purpose of drawing conclusion in a scientific investigation? A conclusion is a statement whether

the results support or falsify the hypothesis

Science progresses and the hypothesis may have to be modified in the future

Scientific Investigation 23

Overall Conclusion – Scientific Investigation

Make observations Formulate a hypothesis Test the hypothesis Draw conclusion

Scientific Investigation 24

Mind Map –Scientific Investigation

framed as a

reveals some

leads to

tested by gathering data in an

may lead to more

may lead to more may lead to

a

Careful observation(s)

Pattern

Conclusion

ExperimentHypothesis

Question(s)