1. Science 7

2. Review From Previous Class
Did you…?
Finish the Twizzler Lab? Name? Hand in?
Finish the Qualitative vs Quantitative Worksheet? Name? Hand in?
Did you finish your Observation and Inference Demo worksheet? Name? Hand in?
What are we up to now?
What are the steps of the scientific method we’ve covered so far?

3. Brainpop-Scientific Method

4. Hypothesis
A hypothesis is: an educated guess or proposition that attempts to explain a set of facts or phenomenon.

5. Hypothesis A hypothesis should always:
Explain what you expect to happen
Be clear and understandable
Be testable
Be measurable
Contain an independent and dependent variable
Ex: Tim and Moby stated their hypothesis as “Fig plants do best if you only water them once a week”

6. Hypothesis
It is usually written in the form: If__________ then ________ will happen because___________________________.
Based on our observations, inferences and background knowledge we can make a TESTABLE hypothesis

7. Variables There are 3 different types of variables
Dependent
Independent
Controlled/Constants
Variables are what changes and can be changed throughout an experiment
Scientists need to be aware of variables so that their experiment is valid

9. Independent Variables
The variable that we intentionally control and change
Ex: Tim and Moby changed the amount of water the plant received

10. Variables Example

11. Dependent Variable
The responding variable, the variable that may or may not change as a result of changing the independent variable
Ex: In Tim and Moby’s experiment it is the plant growth
It depends on manipulation of the independent variable

12. Variables Example

13. Controlled Variables
All other conditions that “can” vary but that we attempt to control in order to prevent our results from being skewed
Ex: Tim and Moby would place all plants in the same window so they receive the same amount of light; they all receive water from the same tap so they are all exposed to the same water contents, and each plant is watered using 2 cups of water so they all receive the same amount per watering etc.

14. Variables Example

15. Variables Worksheet
Identify on the sheet the dependent, independent and controlled (constant) variables for each situation.

16. Hypothesis Writing From your observations and inferences determine:
which part you can control and manipulate (Independent Variable)
Which part we can’t control but what may change based on our other manipulations (dependent variable)
It also doesn’t hurt to identify other variables that may have an effect, but that you would attempt to keep the same in an experiment (controlled variables)

17. Hypothesis Writing
From what you’ve identified you can write your hypothesis in the: “If_____ then_____ because _______” format.
If independent variable, then dependent variable, because _________________.

18. Practice: Writing a Hypothesis
Hypotheses
_________________
Observations
Salt in soil may affect plant growth.
Temperature may cause leaves to change color.
Sunlight causes fruit to ripen more quickly.
Bacterial growth is affected by temperature
Ultraviolet light may cause skin cancer.

19. Practice: Writing a Hypothesis
Hypotheses
If salt in soil affects plant growth, then plants grown in higher salt content soil will grow slower than low salt content soil.
If temperature causes leaves to change color, then plants exposed to cooler temperatures (less than 15°C) should change color faster than plants exposed to warmer temperatures (above 15°C)
If sunlight causes fruit to ripen more quickly, then fruit kept in the dark should ripen slower than fruit kept in direct sunlight.
If bacterial growth is affected by temperature, than food kept at a lower temperature (below 4°C) should have less bacterial growth than food kept at room temperature. (above 4°C)
If ultraviolet light causes skin cancer, then rates of skin cancer occurrence will be higher in people exposed to higher amounts of UV light (ie: tanning bed users, not using sunscreen).
Observations
Salt in soil may affect plant growth.
Temperature may cause leaves to change color.
Sunlight causes fruit to ripen more quickly.
Bacterial growth is affected by temperature.
Ultraviolet light may cause skin cancer.

20. Practice- Worksheet
Using the problem and observations given, create a hypothesis to explain what’s happening.
Describe how you might test your theory
If the page given doesn’t provide enough space please feel free to use the back side or looseleaf
When completed- name and put in Pass In Bin