FINAL EXAM REVIEW

Scientific Method & Measurement

Scientific method and experimental design Each experiment begins with a purpose or problem. This is usually in question form and poses an if… (manipulated variable), then… (responding variable) situation. Example: How does the temperature of the water effect the activity of turtles? What is the manipulated variable in this experiment? Temperature What is the responding variable The activity of turtles

The next part of the experiment is the hypothesis The next part of the experiment is the hypothesis. This is an educated guess based on observations and gathering background information. It is also called an inference. The materials list and procedure follow the hypothesis. Data is collected and interpreted. A conclusion is reached based on the analysis of the data. The conclusion includes a statement as to whether the hypothesis was supported by the data collected during the experiment.

There are 2 types of variables in an experiment Manipulated variable is the part of the experiment that you as the scientist are testing. You are testing to see if a new flavor for jelly beans would be everyone’s favorite – The new flavor would be the manipulated variable. New flavor 2. Responding variable is what happens as a result of your experiment. In the experiment described above, this variable would be how many monkeys chose the new flavor as their favorite.

Steps for Setting up Graphs Effect of temperature on turtle activity Label the x and y axis. Be sure your label includes units! Number each axis. When you set up each axis be certain that the distance between each number is the same. Give your graph a title. A title should describe what the graph is about. Plot the points carefully and connect the dots. Y Manipulated variable Temperature in Co Turtle Activity In strokes Per minute X 2 4 6 8 10 12 14

Measuring Length Length is the distance between two points. Then unit for length is meters (or cm, or mm). Use a meter stick to determine this measurement.

Measuring Mass Mass is the amount of matter in an object. Mass is measured using a triple beam balance or an electronic scale. The unit for mass is grams.

Measuring Volume Volume is the amount of space an object takes up. The unit for volume is cm3 or mL. Volume can be determined in 3 ways: Liquids- use a graduated cylinder Regular shaped object: V=L x W x H Irregular shaped object - use a graduated cylinder to measure the amount of water the object displaces.

Density Density is the amount of mass in a given volume for an object. The unit for density is g/cm3 or g/ml. In other words, density is how tightly packed the molecules are in a substance. Density is determined by dividing the mass by the volume.

Measuring density The density of an object remains the same regardless of the size of the object. The density of water is 1g/cm3. Objects with a density less than 1 will float in water and a density greater than 1 will sink in water.

Using the microscope and measuring field of view If each of the boxes of this field of view is equal to 1 mm, what is the length of this insect on the slide? What is the height of the insect? Remember that measurements in the metric system are not expressed in fractions. So ½ would be .5 mm. 1.0 mm The distance from one side of the field of view can be determined by counting the number of boxes across the field. In this case the field would be 4.0 mm across. 4.0 mm

Using the Microscope When the microscope is in low power you can use the coarse and fine adjustment to view the object on the slide. Under low power, the field of view and the object on the slide will appear very small. When you change the magnification from low to medium power, the object will appear to be larger, and you will see more details. When you change from medium to high power, you will see less of the object because it will appear much larger. However, you will see a lot more detail! REMEMBER: Never use the coarse adjustment knob under high power!

Total magnification= eyepiece X objective A compound microscope has 2 lenses: The eyepiece The objective lens To calculate how much you are magnifying an object you need to know the power of each lens. Total magnification= eyepiece X objective

Using the Microscope When you move the slide to the left while you are looking at the object, it will appear to move to the right. When you move the object away from you, it will appear to be moving toward you. If you wanted to place the insect in the center of the field, how would you move the slides? Up & to the left To the right