Science 7

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?

Brainpop-Scientific Method https://www.brainpop.com/science/scientificinquiry/scientificmethod/

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

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”

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

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

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

Variables Example

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

Variables Example

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.

Variables Example

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

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)

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 _________________.

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.

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.

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