Scientific Method

What is the scientific method? A logical way of solving problems It enables scientists to organize their work

Steps of the scientific method Make Observations/Define the Problem Hypothesis Experiment Analyze Data/Form Conclusions

Define the Problem A scientific problem is usually stated as a question. Ex: Does the amount of water affect how tall a plant grows?

Hypothesis an educated guess should be an answer to the question you posed as your problem

Theory A hypothesis that has stood the test of time In other words, it is strongly supported by a variety of data collected over the years

Experiment – testing your hypothesis Controlled Experiment – all variables are the same except the one being tested A variable is something that you change while doing your experiment Ex: If your variable is the amount of water, you may give some plants 1 liter of water every day, and other plants 2 liters of water. A good experiment only tests 1 variable at a time

Variables: 2 kinds Independent variable – the variable being tested – the one you change (amount of water.) Dependent variable – the change that results from the independent variable. (plant height.)

Experimental Group The group in which the independent variable is changed. Once again, you only test 1 variable at a time. If you want to look at growth in plants, test either amount of food, water, or light…not all 3 at once!

Control Group The group that does not receive the variable being tested. Used as a comparison

Constants Constants are the factors that stay the same with all groups. Example – If you are testing how intensity of light affects plant growth, here are some constants you would use since you will only be changing intensity of light: Amount of food Type of food Species of plant

Validity What should a scientist do if he/she doesn’t get the results they intended? What are some ways to make an experiment more reliable/valid?

Dependent Vs. Independent Variables – please see if you can pick out the dependent vs. the independent variables in each of these examples… George wants to know if different colors of light will affect plant growth. He puts plants under different colors of light and measures their height for 2 months.

Independent Variable colors of light Dependent Variable – plant growth

Dependent Vs. Independent Variables Lucinda wanted to see if her goldfish released more ammonia when given tropical fish food or goldfish food. She divided her 20 goldfish into 2 groups and put them in separate tanks and fed each group a different food for this experiment. She then measured the ammonia content in each aquarium for 6 weeks.

Independent Variable – Type of food Dependent Variable – Ammonia content

Dependent Vs. Independent Variables Charles wanted to know if his aquatic elodea plants would grow better in warm water or cold water. He divided the plants into 2 different tanks with varying water temperatures. He then measured plant height and counted the number of plants for 4 weeks.

Independent Variable – Temperature of water Dependent Variable – Plant height

Dependent Vs. Independent Variables Sally wanted to see if tadpoles grow more quickly if given a protein supplement. She divided 100 tadpoles of the same age and species into 2 groups. She gave 1 group the protein supplement with their food and fed the other group food without the protein. Each week, she would count the number of tadpoles found at various stages of development until they were mature frogs.

Independent Variable – Protein supplement Dependent Variable – Tadpole growth/development Constants? Control Group?

Theory A hypothesis that has stood the test of time. Example: Darwin’s Theory of Evolution Young Darwin Old Darwin

Scientific Laws Events that always occur in nature! Example: Newton’s Law of Gravity

Now, please do this Quia activity! http://www.quia.com/pop/184568.html?AP_rand=921945916