How do scientists design experiments? This activity will introduce you to the concept of variables.

Transcription

1 1.6 (page 1) Science Projects For ALL Students Variables How do scientists design experiments? This activity will introduce you to the concept of variables. Scientists test their ideas by conducting experiments. Every time scientists do experiments, they must look for variables. A variable is any factor in an experiment that affects the results. There are two kinds of variables: independent variables and dependent variables. An independent variable is the part of the experiment that the scientist can control. For example, you may want to see if plant food makes a plant grow faster. You would then take 2 plants of the same size and give one plant food. The plant food is an independent variable. A dependent variable results from a change in an independent variable. In the case of your plants, the eventual size of your plants is a dependent variable. variable independent variable dependent variable Words to Know Safety Precautions Please click on the whistle to view the safety guidelines. Do not perform this experiment in areas where people may be walking. WHAT YOU NEED partner yardstick transparent tape WHAT YOU NEED tennis ball Post-its washable marker 1998 Facts On File, Inc. Published by Facts On File, Inc.

2 1.6 (page 2) WHAT YOU DO PREPARATION 1. Place your desk or table against a wall. Tape the yardstick vertically to the wall behind the desk. The bottom of the yardstick should touch the top of the desk. The yardstick should have the highest number of inches at the top. 2. Label a Post-it 36 inches. 3. Place the Post-it next to that number on the yardstick. Draw a line from that number on the yardstick to your Post-it. 4. Repeat steps 2 and 3 for 30 inches, 24 inches, 18 inches, and 12 inches. ACTIVITY 1. Hold the ball loosely in the palm of your hand next to the 36 inch mark on the yardstick. The height measurement should be at the center of the ball. 2. Tip your hand slightly so that the ball falls

3 1.6 (page 3) Science Projects For ALL Students straight down from the designated height. Do not throw the ball down. 3. Have your partner observe, on the yard stick, the highest point the ball bounces. Use the position of the Post-its to aid your observation. 4. Record that number in the data table under Bounce Height Trial Facts On File, Inc. Published by Facts On File, Inc.

4 1.6 (page 4) 5. Repeat the procedure 2 more times from the same height. Record the bounce numbers under Bounce Height Trial 2 and Bounce Height Trial Average trials 1 through 3. Enter the average in the data table. 7. Repeat steps 1 through 6 for the remaining Drop Heights in the data table. 8. Use the averages from the data table to plot a graph of the relationship between the height of the drop and the height of the bounce. OBSERVATIONS 1. Is the height from which the ball was dropped a dependent or an independent variable? Why? 2. Is the bounce of the ball a dependent or an independent variable? What part of your data supports your answer? 3. Why do you repeat the procedure 3 times for each height and take an average? OUR FINDINGS Click on the above link to see what we found.

5 1.6 (page 5) Science Projects For ALL Students 1998 Facts On File, Inc. Published by Facts On File, Inc.

6 1.6 (page 6) VARIABLES GRAPH Height of Bounce Height from which the ball was dropped

7 Our Findings 1. SKILLS 1.6 VARIABLES 1. The height of the drop was an independent variable because we controlled it. 2. The bounce of the ball was a dependent variable because it varied directly with a change in the drop height of the ball. The graph shows a decrease in bounce with a decrease in height. 3. The more repetitions, the closer to the real value.

8 SAFETY GUIDELINES Special Safety Note To Experimenters Some activities in this book have special safety rules to follow. The special rules are on the page with that activity. But even if every safety rule in the world is included with an experiment, you have to know how to be safe when doing it. So it s very important that you read, copy, and follow the Everyday Safety Rules that follow. Sometimes science experiments can be dangerous. Things can spill, break, or even catch fire. You have to know what to do... fast. So be prepared. Read the directions for each experiment carefully, and follow any special safety rules listed with it, then be careful. Always follow common-sense safety rules like NEVER RUN WITH SCISSORS IN YOUR HAND or BE CAREFUL WITH HOT THINGS! You already know a lot of common-sense safety rules... so remember to follow them, and have fun! Everyday Safety Rules PREPARE Clear off your work space. Read all directions. Know what problems might happen, and be prepared. PROTECT YOURSELF Follow directions step-by-step. Do just one experiment at a time. Locate exits, fire extinguisher, eye wash, and first-aid kit before you start. Ask an adult to show you how to use a fire extinguisher. Be sure there s fresh air in the room. Wear an apron and safety goggles. Don t wear contact lenses, have bare feet, or wear very loose clothing. Keep work space and floor clean. Clean up spills immediately,

9 Don t drink or eat around the experiment work space. Don t eat or drink any stuff tested, unless a grown-up says it s OK. USE EQUIPMENT CAREFULLY Don t set up equipment too near the edge of your work space. Be cautious when using pointed or sharp instruments, like scissors, screwdrivers, or knives. Unplug any electric device by pulling out the plug, not pulling on the cord. Use only low-voltage batteries, like those used in flashlights or smaller. Be careful when using chairs or step-stools. USING CHEMICALS Have an adult help you with all experiments requiring chemicals. Don t inhale or taste chemicals. Read all labels carefully. Label all chemicals. Wear goggles, apron, and gloves so chemicals don t touch your skin. Wash hands before and after using solutions. Wipe up spills thoroughly. HEATING THINGS Wear goggles, apron, and gloves when boiling water. Use safety tongs and heat-resistant mitten or hot pads. Never leave heated things unattended. Turn off hot plates and oven burners when you re finished. Keep flammable things away from heat and flames. Have a fire extinguisher ready. IN THE FIELD Never go on a field trip alone: follow the Buddy System. Tell a responsible grown-up where you re going. Know the area and be aware of dangers, like poisonous plants and deep water Dress for the weather conditions.