Science Buddies: "Ask an Expert"

I am helping my daughter with her science fair project, she chose Return
Up, Up, and Away in Your Own Hot-air Balloon!
We tested how the size of balloon affects the length of time it stays floating. We are done with everything but I am confused as to what is the controlled variable and what is the constant variable in this experiment. They seem very similar in definition and the packet we received from school asks for both.
Thanks

Hello and welcome to the forums:

Science Buddies has a great description of the independent and dependent variables here: https://www.sciencebuddies.org/science- ... bles.shtml. I looked over the experiment, and I think you and your daughter can find these in the "Procedure" section of the experiment. (Hint, look at the data table.)

Finding out the answers to this part of the project is a great way to demonstrate science to your daughter. Scientists have to start every experiment (even every day!) by saying "I don't know the answer to this." Then we investigate and propose solutions. What a great project to introduce young scientists to the scientific process!

Let us know how the experiment worked out!
Best, Keith

Hi!
I looked on your website on variables and many others, but still don't understand what they are. I really need help !

Okay, let's say I want to know how much ketchup tastes the best on a hamburger. I make 10 hamburgers, all exactly the same and put them on 10 identical buns. I put them in the oven to keep them warm and all at exactly the same temperature - 140F.

I then take a bottle of ketchup and a measuring spoon. I pull the burgers out of the oven and put 1tsp of ketchup on the first one. Then 2tsp on the 2nd, 3tsp (1tbsp) on the third and so on until I've put 9tsp or 3tbsp on the 9th. The tenth stays unketchuped (not a real word but it should be) as a control.

I then cut each burger into 4 pieces, *exactly* in 4ths and then call over 4 friends. Each of my friends then takes a bite of each of the burger pieces and writes down their thoughts on whether there was too much, not enough or just the perfect amount of ketchup. I then take the results, put them in a spreadsheet and make a graph.

The burgers were all exactly the same, the ketchup was the same except for the amount, the food was always at the same temperature, the sampling was done by several people and the burgers were eaten in random order. Constants in this experiment? The burger, bun, ketchup ingredients, food temp. Independent variable (the *one* thing I changed between trials) is the carefully measured amount of ketchup and the dependent variable is the result, or which one was deemed to be the tastiest.

The testing itself in this case was subjective and could have been affected by whether my friends were hungry or not, whether they even like ketchup, etc, but it was done as objectively as possible.

Does this make sense? You keep everything the same, change just one thing and then measure one thing. That gives you constants, independent variable and the dependent variable.