Science Skills: Variables For the first 4 problems indicate the independent variable and dependent variable. Follow the directions for Problem 5 as given. Write your answers on a sheet of loose-leaf paper. This is your exit pass for today! Powerpoint adapted from science-class.net

Types of Variables There are 2 main types of variables: Independent Variable: The variable that is changed by the scientist; the ‘I control’ variable Dependent Variable: The variable that might change because of what the scientist changes – what is being measured

Remember! Sometimes your hypothesis can TELL you what your variables are! Ex. If I drink Mountain Dew before bed, then I will not sleep very much. IV: Drinking Mountain Dew DV: the amount of sleep

Practice Use this hypothesis to identify the variables: If I leave all the lights on all day, then my electric bill will be expensive IV: ______________________ DV: ______________________

If I brush my cat more, then there will be less fur on my furniture IV: ______________________ DV: ______________________

A variable is something that can vary or change. What are the variables in this statement? This sample problem will give you the answer in the next slide. The time it takes to run a 10 km race depends on the amount of training the runner does. Click to check your answers

The time it takes to run a 10 km race depends on the amount of training the runner does. The independent variable is the amount of exercise. The dependent variable is the time it takes to run a 10 km race. It is not enough to say just “time” or “training” – you must describe the I.V. and tell how the D.V. is measured.

Now read the following experiment and identify the independent and dependent variables Elizabeth wanted to test if temperature affected how fast milk goes bad and curdles. She left milk in a room temperature closet, a fridge, and a oven that was turned on low heat. She then measured how rotten the milk was after 10 days. IV: ____________________________________ DV: ____________________________________

What are the variables in this statement? The number of puppies in a litter is determined by the weight of the mother dog. Independent variable: Dependent variable:

What are the variables in this statement? The more water a plant gets, the taller it will grow. Independent variable: Dependent variable:

Constants and Controls

Constant Constant: something that scientist makes sure is the same throughout the experiment Ex. Watering the plants the same amount of water or making sure you are testing the same person every time

Control Control: The part of the experiment that the scientist doesn’t change or add the variable to Ex. The plant with the white light

Problem : Lemon trees receiving the most water produce the largest lemons. a. Create a problem question. b. Identify the independent variable: c. Identify the dependent variable: d. List 2 possible constants: e. Explain what you might use for a control.