Density Laboratory - Student Exploration

Name:______________ Date: 3/4/2025 Student Exploration: Density Laboratory Vocabulary: buoyancy, density, graduated cylinder, mass, matter, scale, volume Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1.​ Of the objects below, circle the ones you think would float in water. 2.​ Why do some objects float, while others sink? I think that some objects may float because of their density. For example objects that are more dense than water would sink and things that have less density would float. Hollow things would float too because the air is less dense than water. Gizmo Warm-up The Density Laboratory Gizmo allows you to measure a variety of objects, then drop them in water (or other liquid) to see if they sink or float. 1.​ An object’s mass is the amount of matter it contains. Mass can be measured with a calibrated scale like the one shown in the Gizmo. Drag the first object onto the Scale. (This is object 1.) ​ What is the mass of object 1? The mass of object number 1 is 19.5g. 2.​ An object’s volume is the amount of space it takes up. The volume of an irregular object can be measured by how much water it displaces in a graduated cylinder. A.​ What is the initial volume of water in the cylinder? The volume of the cylinder is 400.0 mL B.​ Place object 1 into the cylinder. What is the volume in the cylinder now? The volume of object number 1 in the cylinder is 414.2mL. C.​ What is the volume of the object? The volume of object number 1 is 14.2cm3. Note: While milliliters (mL) are used to measure liquid volumes, the equivalent unit cubic centimeters (cm3) are used for solids. Therefore, write the volume of object 1 in cm3. Activity A: Float or sink? Get the Gizmo ready: ●​ Drag object 1 back to the shelf. ●​ Check that Liquid density is set to 1.0 g/mL. Question: How can you predict whether an object will float or sink? 1.​ Observe: Experiment with the different objects in the Gizmo. Observe the mass and volume each object, then drag it into the Beaker of liquid to see if it floats or sinks. (Notice a pin holds objects in the graduated cylinder, whether they sink or float.) Try to determine what the floating objects have in common and what the sinking objects have in common. 2.​ Form hypothesis: Compare the floating objects, then do the same for the sinking objects. What do the floating objects have in common? My guess as to why floating objects have in common is that they have less density. Not only that but that also may have some kind of air inside of it to make it float. What do the sinking objects have in common? The sinking object has in common that they have more density 1.0. They also have a higher mass than volume. 3. Collect data: Measure the mass and volume of objects 1 through 12, and record whether they float or sink in the table below. Leave the last column blank for now. Object Mass (g) Volume (cm3) Float or sink? Density (g/cm3) 1 19.5g 14.2cm3 Sink 1.34 (g/cm3) 2 11.1g 9.7cm3 Sink 1.1 (g/cm3) 3 4.3g 5.6cm3 Float 0.77 (g/cm3) 4 134.8g 7.8cm3 Sink 17.8 (g/cm3) 5 3.9g 33.5cm3 Sink 1.1 (g/cm3) 6 78.7g 29.2cm3 Sink 2.70 (g/cm3) 7 2.3g 20.8cm3 Float 0.1 (g/cm3) 8 24.4g 25.7cm3 Float 0.95 (g/cm3) 9 99.6g 43.9cm3 Sink 2.27 (g/cm3) 10 42.1g 60.8cm3 Float 0.69 (g/cm3) 11 65.5g 41.2cm3 Sink 1.59 g/cm3) 12 104.3g 114.1cm3 Float 0.91 (g/cm3) (Activity A continued on next page) Activity A (continued from previous page) 4. Analyze: Look carefully for patterns in your data. A. Does mass alone determine whether an object will float or sink? Explain: No, Because you need volume and mass to dictate whether your object will float or sink. B. Does volume alone determine whether an object will float or sink? Explain: No, because you need mass and volume to determine whether the object will float or sink. C. Compare the mass and volume of each object. What is true of the mass and volume of all the floating objects? Explain: For all floating objects all of their volumes are greater the the mass D. What is true of the mass and volume of all the sinking objects? When the mass is greater than the volume. 5. Calculate: The density of an object is its mass per unit of volume. Dense objects feel very heavy for their size, while objects with low density feel very light for their size. To calculate density, divide the mass by volume: D = m/V. If mass is measured in grams and volume in cubic centimeters, the unit of density is grams per cubic centimeter (g/cm3). Calculate the density of each object, and record the answers in the last column of your data table. Label this column “Density (g/cm3).” 6. Analyze: Compare the density of each object to the density of the liquid, 1.0 g/mL. This is the density of water. What do you notice about the density of the floating objects? All the floating objects densities are less than 1. What do you notice about the density of the sinking objects? All of their densities are greater than 1. 7. Draw conclusions: If you know the mass and volume of an object, how can you predict whether it will float or sink in water? I can predict whether an object will sink or float in water because if the mass is less than the volume the object will most likely float but if the object's mass is greater than the volume the object will sink. Activity B: Liquid density Get the Gizmo ready: ●​ Drag all the objects back onto the shelf. ●​ Check that the Liquid density is still 1.0 g/mL. Question: How does liquid density affect whether objects float or sink? 1.​ Observe: Place object 1 into the Beaker of liquid. Slowly move the Liquid density slider back and forth. What do you notice? As the density increases in the liquid the object will float to the surface. 2.​ Form a hypothesis: Buoyancy is the tendency to float. How do you think the liquid density affects the buoyancy of objects placed in the liquid? I think it affects the buoyancy of abjects placed in the water because if the liquids density is greater than the density of the object i would float. 3.​ Predict: In the table below, write the density of each object. Then predict whether the object will float or sink in each of the fluids. Write “Float” or “Sink” in each empty box of the table. Object Object density 1 Liquid density 0.5 g/mL 1.0 g/mL 2.0 g/mL 1.34 Sink Sink Float 2 1.1 Sink Sink Float 3 0.77 Sink Float Float 4 17.3 Sink Sink Sink 5 1.1 Sink Sink Float 4.​ Test: Test your predictions using Gizmo. Place a checkmark (\/) next to each correct prediction, and an “X” next to each incorrect prediction. 5.​ Draw conclusions: What is the relationship between the object density, the liquid density, and the tendency of the object to float? The reaction sip is that if the object's density is greater than the density of the liquid it will sink. And if the object's density is less than the liquid's density it will float. Extension: King Hieron’s crown Get the Gizmo ready: ●​ Drag all the objects back onto the shelf. ●​ Set the Liquid density to 1.0 g/mL. Introduction: In the third century B.C., King Hieron of Syracuse asked the famous mathematician Archimedes to determine if his crown was made of pure gold. This was a puzzling problem for Archimedes—he knew how to measure the weight of the crown, but how could he measure the volume? Archimedes solved the problem when he got into his bath and noticed the water spilling over the sides of the tub. He realized that the volume of the displaced water must be equal to the volume of the object placed into the water. Archimedes was so excited by his discovery that he jumped out of the bath and ran through the streets shouting “Eureka!” Question: How can you tell if a crown is made of solid gold? 1.​ Think about it: Gold is one of the densest substances known, with a density of 19.3 g/cm3. If the gold in the crown was mixed with a less-valuable metal like bronze or copper, how would that affect its density? I think it would make the gold less dense. 2.​ Observe: Drag each of the crowns into the liquid. Based on what you see, which crown do you think is densest? Explain why you think so. I think Crown B is dencer because it sinks faster. Measure: Find the mass, volume, and density of each of the three crowns. Crown Mass (g) Volume (cm3) Density (g/cm3) A 325.2 62.5 5.20 B 1264.22 65.5 19.3 C 306.0 61.6 4.97 3.​ Draw conclusions: Which of the three crowns was made of gold? Explain: Crown B is made of gold because it’s density is the largest and it had sink the fastest (19.3g/cm).