Chapter 9

Topic 3

Study Guide notes

Item #1

• The metric system is a system of measurement units that is used by scientists and most countries around the world.

• It is used in science so that scientists from different countries can compare measurements using consistent units that they can all relate to.

Item #2

• Accurate and complete measurements require:– The use of precise measurement tools– Multiple measurements by multiple people

• Accurate measurements should be in agreement

– Being labeled with appropriate units• Values for a measurement depend on units

– Being neatly recorded in a table and/or graph

Item #3

• Length of a football field = meters (m)– 1 meter is a little longer than a yard

• Mass of a human adult = kilograms (kg)– 1 kilogram weighs about 2.2 pounds (Earth)

• Volume of a bucket of water = liters (L)– 1 liter is close to a quart (3.8 L = 1 gallon)

• Outdoor air temperature = Celsius degrees – Water freezes at 0 C ; boils at 100 C ; room

temperature is about 15 C

#3 continued

• Length of human foot = centimeters (cm)– 2.54 centimeters = 1 inch

• Mass of a paper clip = grams (g) or milligrams (mg)– A small paper clip is about 0.5 g or 500 mg

• Distance between cities = kilometers (km)– 1.61 kilometers in 1 mile (a 5K run = 3.1 mi)

• Volume of a dose of cough medicine = milliliters (mL)– 1 teaspoon = 5 mL

Canadian road signs

Item #4 - A

• Graphing data using a line graph:– Independent variable plotted on x-axis– Dependent variable plotted on y-axis– Graph is titled (y variable) vs (x variable)– Axes are labeled with units of measurement– Axes should have little “dead space” ; maximum value

should appear near top and minimum value should appear near origin.

– X values increase from right to left; Y values increase from bottom to top

– Increments of units for each grid are equal (take range of values / # of grid spaces to determine scale)

Determining scale for line graph

• Example:– The value for an independent variable ranges from 30

units up to 100 units on a graph that has 20 grid spaces from origin to edge.

– Range of values = 70 units– 70 / 20 = 3.5 per grid– It would be best to scale the graph such that each grid

represents an increment of 4 units, starting with 30 at the origin. This will result in a minimum amount of dead space at the edge and the highest precision in taking readings.

– graph making

Item #4 - B

• The temperature dropped from 18 C down to –52 C as altitude increased from 0 to 15 km.

• At an altitude of 17 km the temperature would be approximately –55 C. (extrapolation)

• At an altitude of 12.5 km the temperature would be approximately –50 C. (interpolation)

• The y-axis (temperature) is the dependent variable ; the x-axis (altitude) is the independent variable.

• As the altitude increased, the temperature decreased.

Item #5

• Relationships between dependent and independent variables may be:– DIRECT : dependent variable increases as a

result of increases in independent variable.– INVERSE : dependent variable decreases as

a result of increases in independent variable. (teeter-totter effect)

Direct proportions

Inverse proportions

Item #7

• A conclusion states whether or not the results of the experiment validate (support) the original hypothesis or not.

• A conclusion is:– Logical (makes sense to most people)– Accurate (correctly reports and interprets

data)– Supported by evidence from the investigation– Relevant to the original hypothesis

Item #8

• Results of investigations should be communicated to others so that they may repeat the experiment in an effort to verify results.

• Allowing others to review procedures, data, and conclusions helps to reduce the risk of bias and encourages others to build on what was learned.