Pre-Lab 2B: Density

Lab requirements: remember? KQ Bkgd Drawing Skip lines Section: number All questions AND answers Data charts: rules, resolution, units, accuracy

Purpose You may be familiar with the trick question “Which is heavier: a kilogram of feathers or a kilogram of bricks?” What is the trick? In this investigation you will study the relationship between mass, volume, and density. You will also determine how an object’s density affects whether it sinks or floats in water.

Key Question How is an object’s density related to its volume, mass, and tendency to sink or float?

Background Define: line of best fit density (formula) slope (formula)

Drawing A kilogram of feathers and an equal mass of bricks

Procedure Section 1: measuring mass and volume Demo water displacement in grad. cylinder Use 6 objects which are the EXACT SAME (all nuts, or bolts, or screws); MUST RECORD TYPE AND COLOR OF OBJECT Find mass (? Decimals), volume (? Decimals), never put units IN w/data: on header bar only, why? How many items are you measuring/why (data chart)? Graph data: MAKE A LINE GRAPH Leave room for extending the graph’s BFL up through the top right: this is a key point, remember it!!!!!!!!

Section 2: How do you find the best fit line? What is slope? Show slope work on graph!!!! Include labeling the two points w/ coordinates you use on the bfl What is the formula for slope? Section 3: Use your graph’s BFL to predict all six objects’ mass: predict a point from 6th volume to the BFL line to the y-axis intercept: show example…….. Section 4: Use your data and get data from 5 additional lab groups in table 2, to answer density questions

Section 5: OMIT: DO NOT DO THIS SECTION Section 6: Predict if cubes will float or sink in water: what is this prediction really called? must occur before you collect data What is the density of water? Section 8: Test your hypothesis

Post Lab 2B: Density You may be familiar with the trick question “Which is heavier: a kilogram of feathers or a kilogram of bricks?” What is the trick? In this investigation you studied the relationship between mass, volume, and density. You also determined how an object’s density affects whether it sinks or floats in water.

Background Define: density (formula) line of best fit slope (formula)

Does density depend on the size of the material? Evidence? Does density depend on the type of material? Evidence? Using what you have observed in this lab, do you suppose that density depends on the shape of the material? Why or why not? What is the density of water?

Describe two different ways you can find the density of a regularly-shaped object like a cube. Explain why two different objects can have equal volumes but different masses. Which method of prediction was better, testing the weight of the cube in your hand, or comparing the density of the cube to the density of water? Why?