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 makinggraph 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.