Writing Hypotheses

Learning Scale for Scientific Inquiry (SC. 8. N. 1. 1, SC. 7. N. 1 Learning Scale for Scientific Inquiry (SC.8.N.1.1, SC.7.N.1.2, SC.7.N.1.5) 4 (All of 3 +) – Evaluate a scientific investigation based on the evidence provided. 3 (All of 2 +) – Interpret and analyze data. Describe and analyze the methods used in science. 2 (All of 1 +) – Differentiate between test and outcome variables. Differentiate between repetition and replication. 1 - Identify and describe the steps of scientific inquiry.

What is a hypothesis? A hypothesis is an educated guess or possible explanation. This means that it is a statement of what you think the answer is based on your research and prior knowledge.

An Example of a Hypothesis If the number of seeds planted in a flower pot is increased, then the seedlings will be smaller due to the limiting factor of space. The hypothesis is a complete sentence or paragraph that states: A possible answer The reason for your answer

Not a Hypothesis A hypothesis is NOT: A question Written in first person (I think…, My hypothesis is…, etc.) A yes or no answer An explanation of the experiment Non Example: I don’t like snakes because they are slimy.

Why are hypotheses valuable? They set the scene for your experiment. You have a goal and you try to prove it true.

Does it matter if your hypothesis is wrong? No – You still find the answer to your problem. The hypothesis was just an educated guess.

Things to Remember Must be testable Must relate to your question Write as an if/then/because statement

John wants to know which ball bounces higher John wants to know which ball bounces higher. He has a golf ball, bouncy ball, and tennis ball. What could his hypothesis be? I think the bouncy ball will bounce higher. The golf ball will bounce higher than the tennis ball. If the balls are dropped, then they will bounce because they are elastic. If the tennis ball is dropped, then it will bounce higher because it contains more rubber material.

John wants to know which ball bounces higher John wants to know which ball bounces higher. He has a golf ball, bouncy ball, and tennis ball. What could his hypothesis be? I think the bouncy ball will bounce higher. The golf ball will bounce higher than the tennis ball. If the balls are dropped, then they will bounce because they are elastic. If the tennis ball is dropped, then it will bounce higher because it contains more rubber material.

Michelle wants to test the affect of salt water on plants Michelle wants to test the affect of salt water on plants. Which one is the best hypothesis? If plants are grown with salt water then they will die. If plants are watered with salt water, then the plants will wither and die because they will dehydrate. If salt water is used, then all will die because of the salt. If salt water and water are used, then the plants will grow faster because they get double the water.

Michelle wants to test the affect of salt water on plants Michelle wants to test the affect of salt water on plants. Which one is the best hypothesis? If plants are grown with salt water then they will die. If plants are watered with salt water, then the plants will wither and die because they will dehydrate. If salt water is used, then all will die because of the salt. If salt water and water are used, then the plants will grow faster because they get double the water.

What is a Variable?

DEFINITION Variable – Any factor that can change in a scientific investigation or experiment

Types of Variables Test/Independent Variable The condition that is intentionally changed by the investigator in an experiment There can be only one in an experiment Ask the question: What are we changing?

Types of Variables Outcome/Dependent Variable The factors or conditions that will change The factors that you measure or observe as data There can be one or more Ask the question: What am I trying to observe or measure?

Types of Variables Controlled Variables/Control Group The factors or conditions that are kept the same (unchanged) in an experiment. There are many controlled variables in an experiment

Identify variables for the following experiments. Practice Identify variables for the following experiments. You can do it!

Testable Question #1 Does changing the temperature of a ball affect the height the ball will bounce? Cold Hot

Identify Variables #1 Does changing the temperature of a ball affect the height the ball will bounce? Test/Independent Variable Cold Hot Outcome/Dependent Variable

Identify Variables #1 Controlled Variables: * Same ball * Dropped from the same height * Dropped onto the same surface * etc…

Testable Question #2 Does changing the color of light affect the growth rate of plants?

Identify Variables #2 Does changing the color of light affect the growth rate of plants? Test/IndependentVariable Outcome/Dependent Variable

Identify Variables #2 Controlled Variables: * Same type / size of plant * Same wattage of bulb * Same amount of water * Same soil * Light on for the same amount of time * etc…

Testable Question #3 How does the size of a parachute affect the time it takes a hippo to fall 10 feet?

Identify Variables #3 How does the size of a parachute affect the time it takes a hippo to fall 10 feet? Test/Independent Variable Outcome/Dependent Variable

Identify Variables #3 Controlled Variables: * Same hippo * Dropped from the same height * Same parachute fabric * Same length of strings on the parachute * etc…

Sam wants to test which color of light plants grow best in Sam wants to test which color of light plants grow best in. He uses the same type of plant and the same amount of water for each plant. He places 5 plants in sunlight, 5 plants in black light, and 5 plants in red light. What is the test variable? What is the outcome variable? What is the controlled variable?

Sam wants to test which color of light plants grow best in Sam wants to test which color of light plants grow best in. He uses the same type of plant and the same amount of water for each plant. He places 5 plants in sunlight, 5 plants in black light, and 5 plants in red light. What is the test variable? Type of light What is the outcome variable? Plant growth What is the controlled variable? Plants grown in sunlight

Learning Scale for Scientific Inquiry (SC. 8. N. 1. 1, SC. 7. N. 1 Learning Scale for Scientific Inquiry (SC.8.N.1.1, SC.7.N.1.2, SC.7.N.1.5) 4 (All of 3 +) – Evaluate a scientific investigation based on the evidence provided. 3 (All of 2 +) – Interpret and analyze data. Describe and analyze the methods used in science. 2 (All of 1 +) – Differentiate between test and outcome variables. Differentiate between repetition and replication. 1 - Identify and describe the steps of scientific inquiry.