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Standard 9a and 9b

- Plan and conduct a scientific Investigation to test a hypothesis.
- Evaluate the accuracy and reproducibility of data

What does the word hypothesis mean?

- Hypothesis is an educated guess.
- It has to be something you can test not just an opinion
- Example: Cold water freezes faster than hot water.

There are 3 types of variables in an experiment.

- Control variable: variables that are kept the same throughout the whole experiment.
- Independent variable: Also called the experimental variable or manipulated variable. It is the thing the scientist is changing.
- Dependent variable: what the scientist is measuring. It responds to what is being done with the experimental variable.

A good experiment only tests 1 variable at a time

- It’s important to test 1 variable at a time so you know exactly what is causing your results.

Doing an experiment more than once is good.

- Experiments need to have reliable data so that good conclusions can be made.
- Reproducibility is when you repeat an experiment or measurement the same way you get the same answer.
- Multiple trials help ensure reproducibility because errors can be seen more easily.

Your turn: Read the Following procedure carefully

- EXPERIMENTAL PROCEDURE
- Fill 3 containers with 300 milliliters of cold tap water.
- 2. Add 10 grams of salt to container 1; stir. Add 20 grams of salt to Container 2; stir. Add no salt to container 3.
- Place the 3 containers in a freezer.
- Check the containers every 15 minutes. Record your observations.

What is the experimental variable?

- EXPERIMENTAL PROCEDURE
- Fill 3 containers with 300 milliliters of cold tap water.
- 2. Add 10 grams of salt to container 1; stir. Add 20 grams of salt to Container 2; stir. Add no salt to container 3.
- Place the 3 containers in a freezer.
- Check the containers every 15 minutes. Record your observations.

What is probably the dependent variable?

- EXPERIMENTAL PROCEDURE
- Fill 3 containers with 300 milliliters of cold tap water.
- Add 10 grams of salt to container 1; stir. Add 20 grams of salt to Container 2; stir. Add no salt to container 3.
- Place the 3 containers in a freezer.
- Check the containers every 15 minutes. Record your observations.

What is a control variable?

- EXPERIMENTAL PROCEDURE
- Fill 3 containers with 300 milliliters of cold tap water.
- Add 10 grams of salt to container 1; stir. Add 20 grams of salt to Container 2; stir. Add no salt to container 3.
- Place the 3 containers in a freezer.
- Check the containers every 15 minutes. Record your observations.

What is a possible hypothesis?

- EXPERIMENTAL PROCEDURE
- Fill 3 containers with 300 milliliters of cold tap water.
- Add 10 grams of salt to container 1; stir. Add 20 grams of salt to Container 2; stir. Add no salt to container 3.
- Place the 3 containers in a freezer.
- Check the containers every 15 minutes. Record your observations.

Where is there a possible error?

Freezing Time Results

Trial 1 Trial 2

- 10 grams 10 minutes 13 minutes
- 20 grams 13minutes 13 minutes
- No salt 8 minutes 8 minutes

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