What is a Hypothesis?What is a Hypothesis?

How does a hypothesis begin?How does a hypothesis begin?

What do you do with it?What do you do with it?

How do you make one?How do you make one?

How does a hypothesis begin?How does a hypothesis begin?

Scientists make lots of observations. This Scientists make lots of observations. This leads them to form scientific questions leads them to form scientific questions about what they have observed. Each about what they have observed. Each scientist creates an explanation – or scientist creates an explanation – or hypothesis – that he or she thinks will hypothesis – that he or she thinks will answer the question.answer the question.

How does a hypothesis begin?How does a hypothesis begin?

A scientist bases his/her hypothesis both on A scientist bases his/her hypothesis both on what he or she has observed, and on what what he or she has observed, and on what he or she already knows to be true.he or she already knows to be true.

Making a hypothesis is a step in the Making a hypothesis is a step in the Scientific MethodScientific Method

The 7 basic steps of the scientific method:The 7 basic steps of the scientific method:1.1. Asking a questionAsking a question2.2. Completing researchCompleting research3.3. Making a hypothesisMaking a hypothesis4.4. Planning an investigationPlanning an investigation5.5. Recording and analyzing dataRecording and analyzing data6.6. Explaining the dataExplaining the data7.7. Communicating the resultsCommunicating the results

Example questionExample question

A scientist notices that the tomato plant closest A scientist notices that the tomato plant closest to her neighbor’s yard is much taller than any of to her neighbor’s yard is much taller than any of the other plants in her garden bed. She also the other plants in her garden bed. She also notices that the neighbor turns on his sprinkler notices that the neighbor turns on his sprinkler system every day, and that some of this water system every day, and that some of this water reaches only her big plant. The scientist creates reaches only her big plant. The scientist creates a question: Does daily watering from a sprinkler a question: Does daily watering from a sprinkler make a tomato plant grow faster than other make a tomato plant grow faster than other tomato plants?tomato plants?

Example hypothesisExample hypothesis

The scientist creates this hypothesis to The scientist creates this hypothesis to address her question: “If I water the address her question: “If I water the tomatoes in my garden daily then they will tomatoes in my garden daily then they will grow faster because tomatoes grow more grow faster because tomatoes grow more when they get more water.”when they get more water.”

What do you do with a hypothesis?What do you do with a hypothesis?

The hypothesis that a scientist creates leads The hypothesis that a scientist creates leads him or her to make a prediction that can him or her to make a prediction that can be tested next in an investigation. be tested next in an investigation.

What do you do with a hypothesis?What do you do with a hypothesis?

Notice how the example scientist’s Notice how the example scientist’s hypothesis makes a prediction that can be hypothesis makes a prediction that can be tested: tested:

“ “If I water the tomatoes in my garden If I water the tomatoes in my garden daily then they will grow faster because daily then they will grow faster because tomatoes grow more when they get more tomatoes grow more when they get more water.”water.”

What will the scientist do in the What will the scientist do in the investigation to test her hypothesis?investigation to test her hypothesis?

A hypothesis is not just a predictionA hypothesis is not just a prediction

In science a prediction is an educated In science a prediction is an educated guess about the expected outcome of a guess about the expected outcome of a specific testspecific testIn science a hypothesis goes furtherIn science a hypothesis goes furtherA hypothesis includes a possible A hypothesis includes a possible explanation about why the expected explanation about why the expected outcome of a test will occuroutcome of a test will occur

Prediction vs. hypothesisPrediction vs. hypothesis

Example Prediction: If it gets cold outside Example Prediction: If it gets cold outside the leaves will change colors.the leaves will change colors.

Example Hypothesis: If it gets cold Example Hypothesis: If it gets cold outside then the leaves will change color outside then the leaves will change color because leaf color change is related to because leaf color change is related to temperature.temperature.

How do you write a hypothesis?How do you write a hypothesis?

A good hypothesis includes two parts: A good hypothesis includes two parts:

1. a prediction about the outcome of a 1. a prediction about the outcome of a

scientific investigation scientific investigation

----and--------and----

2. an explanation for why those results 2. an explanation for why those results

will occurwill occur

How do you write a hypothesis?How do you write a hypothesis?

A hypothesis is worded as a prediction A hypothesis is worded as a prediction about what will happen if you change about what will happen if you change somethingsomething

Example: If students eat a lot of candy Example: If students eat a lot of candy then they will get more cavities because then they will get more cavities because sugar on teeth causes cavities.sugar on teeth causes cavities.

How do you write a hypothesis?How do you write a hypothesis?

A good hypothesis is worded like this:A good hypothesis is worded like this:

If…..then…...because…….If…..then…...because…….

OROR

I predict…becauseI predict…because

I think…becauseI think…because

Hypothesis exampleHypothesis example

IfIf students eat a lot of chocolate students eat a lot of chocolate thenthen they they will get a sick stomach will get a sick stomach becausebecause a lot of a lot of

chocolate all at once is hard for the chocolate all at once is hard for the stomach to digest.stomach to digest.

If….then….because….If….then….because….

After the word “If”… explain what will After the word “If”… explain what will change in the investigationchange in the investigation

After the word “then” …write what you After the word “then” …write what you predict will happen as a result of that predict will happen as a result of that changechange

After the word “because” …explain why After the word “because” …explain why you think the result will happen you think the result will happen

Another hypothesesAnother hypotheses

IfIf salt is added to a plant’s soil salt is added to a plant’s soil thenthen the the plant will die plant will die becausebecause salt will dry out the salt will dry out the soil so that there is not enough water left soil so that there is not enough water left for the plant.for the plant.

Another HypothesisAnother Hypothesis

IfIf people spend more time in the sun people spend more time in the sun thenthen they will be more likely to get skin cancer they will be more likely to get skin cancer becausebecause exposure to ultraviolet light in exposure to ultraviolet light in sunlight causes skin cancer.sunlight causes skin cancer.