The Physical Sciences

Chapter Two: Science and Measurement

• 2.1 Inquiry and the Scientific Method

• 2.2 Distance, Time, and Speed

• 2.3 Experiments and Variables

2.3 Variables and Relationships

• A variable is a well-defined piece of information with a name and a value.

• Which is the variable and which is the value?

2.3 Experiments and variables• An experiment is a

situation specially set up to investigate the relationships between specific variables.

• Experiments test whether or not a hypothesis has scientific support.

2.3 Controlled Experiments• In a controlled experiment only one

variable is changed at a time.

2.3 Experiments and variables• The variables that you keep the same are

called control variables.

• The variable you change in an experiment is called the experimental variable.

2.3 Error• Error is the difference between a

measurement and the true value of what is measured.

Which of these values is has the LEAST amount of error?

Which value has the MOST error?

2.3 Averages• When you make many measurements of the same

thing you will notice that the values cluster around an average.

• To calculate an average, add up all the measurements and divide by the total number of measurements.

• Some measurements are more than the average and some are less.

How are averages useful?

2.3 Accuracy• In science, the word accuracy means how

close a measurement is to the true value of what is being measured.

Which of these values is the MOST accurate?

2.3 Estimating Error• In science, two measurements are considered

the same if their difference is less than or equal to the average of the measurments.

2.3 Significant difference

• Is the data from these two groups significantly different?

• Why or why not?

2.3 Drawing Conclusions• The point of experiments is to produce data

that allows scientists to come to conclusions.

Does either group’s data gives a more valid conclusion about the hypothesis?

Technology Connection

• Human eyes cannot see infrared light.

Amazing Infrared

• Let’s check out your TV, DVD, or stereo remote control device.

Activity

• A clock is a tool used to measure time.

• Inside a clock are parts that move with a constant repetition.

Make a Water Clock