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Browse Science Projects. Award winning educational materials designed to help kids succeed. Start for free now!

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You may work in groups but must write up your CBA on your own. You can chose to present it in a word document, poster or a powerpoint. The headings you need to follow are also on this padlet, in Structure (see below). We have three weeks of school time to complete your CBA. Good luck…….

There are some ideas also below.

Also, please read Lab Safety Rules and know the dangers!

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Science CBA 1 Ideas

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CBA 1 - Structure

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Lab safety

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Some Even More Examples!

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Some More Examples

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More Still!

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Poster Layout

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Plan

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Developing Questions

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Short report

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Full report

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Browse Science Projects

Over 1,200 free science projects for K-12. Browse by subject, grade level, or try our Topic Selection Wizard to find your winning science project. With science projects in 32 different areas of science from astronomy to zoology, we've got something for everyone!

Let us help you find a science project that fits your interests, with our Topic Selection Wizard.

15 Best Science Projects - Our Scientists' Picks

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Over 1,200 free science projects searchable by subject, difficulty, time, cost and materials. Browse the library or let us recommend a winning science project for you!

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What is a Hypothesis?

A hypothesis is a tentative, testable answer to a scientific question. Once a scientist has a scientific question she is interested in, the scientist reads up to find out what is already known on the topic. Then she uses that information to form a tentative answer to her scientific question. Sometimes people refer to the tentative answer as "an educated guess." Keep in mind, though, that the hypothesis also has to be testable since the next step is to do an experiment to determine whether or not the hypothesis is right!

A hypothesis leads to one or more predictions that can be tested by experimenting.

Predictions often take the shape of "If ____then ____" statements, but do not have to. Predictions should include both an independent variable (the factor you change in an experiment) and a dependent variable (the factor you observe or measure in an experiment). A single hypothesis can lead to multiple predictions, but generally, one or two predictions is enough to tackle for a science fair project.

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Examples of Hypotheses and Predictions

What if My Hypothesis is Wrong?

What happens if, at the end of your science project, you look at the data you have collected and you realize it does not support your hypothesis? First, do not panic! The point of a science project is not to prove your hypothesis right. The point is to understand more about how the natural world works. Or, as it is sometimes put, to find out the scientific truth. When scientists do an experiment, they very often have data that shows their starting hypothesis was wrong. Why? Well, the natural world is complex-it takes a lot of experimenting to figure out how it works-and the more explanations you test, the closer you get to figuring out the truth. For scientists, disproving a hypothesis still means they gained important information, and they can use that information to make their next hypothesis even better. In a science fair setting, judges can be just as impressed by projects that start out with a faulty hypothesis; what matters more is whether you understood your science fair project, had a well-controlled experiment, and have ideas about what you would do next to improve your project if you had more time. You can read more about a science fair judge's view on disproving your hypothesis at Learn More About the Scientific Method.

It is worth noting, scientists never talk about their hypothesis being "right" or "wrong." Instead, they say that their data "supports" or "does not support" their hypothesis. This goes back to the point that nature is complex-so complex that it takes more than a single experiment to figure it all out because a single experiment could give you misleading data. For example, let us say that you hypothesize that earthworms do not exist in places that have very cold winters because it is too cold for them to survive. You then predict that you will find earthworms in the dirt in Florida, which has warm winters, but not Alaska, which has cold winters. When you go and dig a 3-foot by 3-foot-wide and 1-foot-deep hole in the dirt in those two states, you discover Floridian earthworms, but not Alaskan ones. So, was your hypothesis right? Well, your data "supported" your hypothesis, but your experiment did not cover that much ground. Can you really be sure there are no earthworms in Alaska? No. Which is why scientists only support (or not) their hypothesis with data, rather than proving them. And for the curious, yes there are earthworms in Alaska.

What Makes a Good Hypothesis?

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Writing a Hypothesis for Your Science Fair Project

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A hypothesis is a tentative, testable answer to a scientific question. Once a scientist has a scientific question she is interested in, the scientist reads up to find out what is already known on the topic. Then she uses that information to form a tentative answer to her scientific question.

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Which Brand of Battery Lasts the Longest | Science Project Ideas

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While going out on expeditions, it is useful to know the brand of battery that lasts the longest as it would ensure a hassle-free trip without hunting for the basics. You would be interested to know that the process of finding it out constitutes a great science fair project outing for kids. Here com…

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Egg in Vinegar Experiment | Science Project Ideas

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The egg in vinegar experiment, though pretty simple, gives your child the foundation knowledge on reactions between acids and bases. It goes on to change the chemical composition of an egg, making it rubbery on being dipped in vinegar for a few days. There are minor changes in the size of the egg to…

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What are Variables?

What are Variables?

In science, a variable is any factor, trait, or condition that can exist in differing amounts or types.

Scientists try to figure out how the natural world works.To do this they use experiments to search for cause and effect relationships. Cause and effect relationships explain why things happen and allow you to reliably predict the outcomes of an action. Scientists use the scientific method to design an experiment so that they can observe or measure if changes to one thing cause something else to vary in a repeatable way.

These factors that change in a scientific experiment are variables.

A properly designed experiment usually has three kinds of variables: independent, dependent, and controlled.

What is an Independent Variable?

The independent variable is the one that is changed by the scientist. Why just one? Well, if you changed more than one variable it would be hard to figure out which change is causing what you observe. For example, what if our scientific question was: "How does the size of a dog affect how much food it eats?"; then, during your feeding experiments you changed both the size of the dog and the time of day the dogs were fed. The data might get a bit confusing- did the larger dog eat less food than the smaller dog because of his size or because it was the middle of the day and dogs prefer to eat more in the morning?

Sometimes it is impossible to just change one variable, and in those cases, scientists rely on more-complicated mathematical analysis and additional experiments to try to figure out what is going on. Older students are invited to read more about that in our Experimental Design for Advanced Science Projects page. To be clear though, for a science fair, it is usually wise to have only one independent variable at a time. If you are new to doing science projects and want to know the effect of changing multiple variables, do multiple tests where you focus on one independent variable at a time.

What is a Dependent Variable?

The dependent variables are the things that the scientist focuses his or her observations on to see how they respond to the change made to the independent variable. In our dog example, the dependent variable is how much the dogs eat. This is what we are observing and measuring. It is called the "dependent" variable because we are trying to figure out whether its value depends on the value of the independent variable. If there is a direct link between the two types of variables (independent and dependent) then you may be uncovering a cause and effect relationship. The number of dependent variables in an experiment varies, but there can be more than one.

What is a Control Variable?

Experiments also have controlled variables. Controlled variables are quantities that a scientist wants to remain constant, and she or he must observe them as carefully as the dependent variables. For example, in the dog experiment example, you would need to control how hungry the dogs are at the start of the experiment, the type of food you are feeding them, and whether the food was a type that they liked. Why? If you did not, then other explanations could be given for differences you observe in how much they eat. For instance, maybe the little dog eats more because it is hungrier that day, maybe the big dog does not like the dog food offered, or maybe all dogs will eat more wet dog food than dry dog food. So, you should keep all the other variables the same (you control them) so that you can see only the effect of the one variable (the independent variable) that you are trying to test. Similar to our example, most experiments have more than one controlled variable. Some people refer to controlled variables as "constant variables."

In the best experiments, the scientist must be able to measure the values for each variable. Weight or mass is an example of a variable that is very easy to measure. However, imagine trying to do an experiment where one of the variables is love. There is no such thing as a "love-meter." You might have a belief that someone is in love, but you cannot really be sure, and you would probably have friends that do not agree with you. So, love is not measurable in a scientific sense; therefore, it would be a poor variable to use in an experiment.

Examples

Examples of Variables

Time as an Example of an Independent Variable

In some experiments, time is what causes the dependent variable to change. The scientist simply starts the process, then observes and records data at regular intervals.

The Independent Variable for Surveys and Tests of Different Groups

When a scientist performs a test or survey on different groups of people or things, those groups define the independent variable. For example:

Either/Or (Binary) Variables

Sometimes a variable simply represents an either/or (binary) condition. For example, something might be either present or not present during an experiment.

Sample

Sample

Here is a sample containing the variables and hypothesis.

Checklist

Science Fair Project Variables Checklist

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How to use dependent, independent, and controlled variables in your science experiments.

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How To Write A Hypothesis For A Research Proposal

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The Scientific Method Part 2: Variables and Hypothesis