Topic #1.1Variables & Relationships

OutcomesA2 – Analyze graphs or charts of situations to identify specific informationC10 – Describe real-world relationships depicts by graphs, tables of values and written descriptions

Think about it…Tree farming is an important business in

Atlantic Canada. Tree farmers want to make sure that each year there are enough Christmas trees of the right size to sell. When tree farmers try to predict the size of trees, they must consider the factors that affect growth.

Questions:1.Why is it important to predict the size of trees

from year to year?2.How are Christmas trees priced?3.How can this help the farmer to predict income?

Mind MappingVisual graphics that show relationships

between factors.

Add the following 4 factors to the mind map below:Wind speed;Number of pests that live in the trees;Amount of space that the trees have in which to grow;Number of people available to tend the tree farm

Adequate rainfall increases growth

Lightning can cause forest fires

Pollution from cars can slow growth

Add at least 2 other factors you can think of that can affect tree growth.

Which factors can the farmer control?Factors the farmer can control How the farmer can control them:

Types of VariablesIndependent variable: A factor that

affects another factor in an experiment or a relationship.

Dependent Variable: The factor that is affected by the other factors in an experiment of a relationship. It can be thought of as the result or “what you measure”. This “depends” on what you did to it.

For example:

How well you do on a test might depend on the number of classes you attended, how much you

participated in the class activities, or how long you studied for the test.

In this example, what you measure (the result) is your test score. It is the DEPENDENT VARIABLE. What you did to achieve your test score (attending class,

participating in class activities and length of time studying) are the INDEPENDENT

VARIABLES.

Control VariablesIn order to know exactly how one particular variable

will affect another, you must hold all other possible variables constant.

You must make sure that only one variable changes during an experiment and everything else is kept the same.

All the other factors that might possibly affect the results of your experiment are known as “CONTROL VARIABLES”.

For example, if you want to know what affect light will have on the growth of tomato plants, WHAT WOULD YOU DO?

Control VariablesWhat did you suggest?

Grow many plants (e.g. 10 plants)Use 10 identical pots,Add exactly the same amount and type of soil to each pot, Plant the same number and type of seeds in each pot, Add the same type and amount of fertilizer to each pot, andWater the pots with the same amount of water.

The ONLY thing that should be different is the amount of light you expose each of the plants to during the experiment.

That way you will know that any difference between the plants is caused by the different light conditions and not some other variable.

Journal Entry #1

Write a reflection on your understanding of variables.

Describe at least one other the real-world cause-and-effect relationship.

Identify the independent, dependent and control variables.

Check you Understanding #11. Identify the independent and dependent

variables in each of the followingSituation Independent Variable Dependent Variable

AJim says that the amount of lumber that he can cut depends upon the time that he spends in the woods

B

Karina says that the amount of time that you spend walking to school depends mainly on the distance of your home from the school.

CKim earns more money in a 6 hour shift that she earns in a 4 hour shift.

D

Rob drives a transport truck. He is interested in the relationship between the amount of diesel fuel he uses and the size of the load in the trailer.

Check you Understanding #1Complete the following table:

DescriptionCause-and-Effect

Relationship (Yes or No)

Variables

Dependent Variable Independent Variable

AThe length of a candle and the amount of time it has been burning.

BThe mark you get on a test and the time you spend studying.

CThe speed of a car and the distance from the nearest gas station.

D The length of a movie and the admission price.E The age of a car and its current value.

FThe population of a community and its distance from the coast.

GThe faster you drive and the number of speeding tickets you receive.

HThe length of a beach and the size of the waves that crash on it.

IThe number of pages of the test paper and the time permitted to write the exam.

Check you Understanding #1Ski jumping is a popular event at the Winter

Olympic Games. The following factors may affect the distance a skier jumps:Length of the ramp;Force with which the skier pushes to start;Wind speed;Wind direction;Model of the skis;Slope of the ramp.

Draw a mind map to illustrate the relationships between the dependent and the independent variables.

Check you Understanding #1Factors the skier can control Factors the Jump Designer can control Factors outside the control of anyone

Check you Understanding #1Taylor wants to see how the prices of various

types of trees depend upon the height.

Douglas Fir, 2.4m, $25

Douglas Fir, 2.0m, $15

Douglas Fir, 2.2m, $20

White pine, 2.0m, $20

White pine, 2.4m, $35

White pine, 2.2m, $25

Scotch Pine, 2.6m, $55

Scotch Pine, 2.2m, $40

Scotch Pine, 2.0m, $30

Example of your bar graph…