Gizmos Answer Key - Density

Density Answer Key Vocabulary: density, mass, matter, volume Prior Knowledge Questions (Do these BEFORE using the Gizmo.) [Note: The purpose of these questions is to activate prior knowledge and get students thinking. Students are not expected to know the answers to the Prior Knowledge Questions.] 1. List three objects that you think would sink in water, and three objects you think would float. Sink: Answers will vary. Float: Answers will vary. 2. Why do you think some things float and some things sink? Answers will vary. Gizmo Warm-up 1. In the Gizmo™ select an object and drag it onto the scale. Mass is the amount of matter, or "stuff," in an object. A. Which object did you choose? Answers will vary. B. What unit of measurement is used for mass? Grams (g) C. What is the object's mass? [Check mass in table below.) 2. Drag the object into the graduated cylinder. The number above the cylinder gives the volume, or the amount of space the object takes up. The unit milliliter (mL) is used for liquids, while the unit cubic centimeters (cm³) is used for solids. One milliliter is the same volume as one cubic centimeter. (In the Gizmo, notice a pin inside the graduated cylinder holds objects in place, even if they float.) A. Which object did you choose? Answers will vary. Graduated cylinder B. What is your object's volume, in cm³? [Check table below. (This is equal to the volume in mL.) C. Drop the object into the beaker of water. Does it sink or float? [Check answer below] Object Ping Pong Golf Ball Toy Soldier Apple Chess Penny Egg Rock Gold 1 Crown Crown 2 Mass (g) 3.0 45.0 120.0 33.0 40.0 3.0 65.0 200 579 840.0 1930 Volume (cm³) 36.0 36.0 80.0 44.0 80.0 0.4 64.0 50.0 30.0 100.0 100.0 Float or Sink? Float Sink Sink Float Float Sink Sink Sink Sink Sink Sink Activity A: Sink or float? Get the Gizmo ready: Replace all objects on the shelf. Be sure the liquid in the beaker is Water. Question: How do mass and volume affect sinking and floating? 1. Predict: Which objects will float in water? Which will sink? Record your predictions below. Object Prediction (sink or float?) Mass (g) Volume (cm³) Result (sink or float?) Ping pong ball Answers will vary 3 36 float Golf ball Answers will vary 45 36 sink Apple Answers will vary 33 44 float Chess piece Answers will vary 40 80 float Penny Answers will vary 3 0.4 sink Rock Answers will vary 200 50 sink 2. Experiment: Use the Gizmo to find the mass and volume of each object and whether it floats or sinks. Record your results in the table. 3. Analyze results: Look at the data in your table. A. Can you use mass alone to predict whether an object will sink or float? Explain. No, there isn't a pattern in the numbers. For example, the ping pong ball and the penny have the same mass, but one floats and one sinks. B. Can you use volume alone to predict whether an object will sink or float? Explain. No, there isn't a pattern in these numbers either. For example, the ping pong bali and the golf ball have the same volume, but one floats and one sinks. 4. Draw conclusion: Can you use mass and volume to predict whether an object will sink or float in water? Explain your thinking. Yes, there is a pattern. If the mass [in grams] is less than the volume [in cm³), the object floats. If the mass (in grams] is greater than the volume (in cm³], the object sinks. 5. Apply: Measure the mass and volume of the toy soldier: Mass 120 g Volume 80 cm³ Will it float or sink? Sink Use the Gizmo to test your prediction. [It sinks.] Activity B: Calculating density Get the Gizmo ready: Replace the objects on the shelves. Be sure the liquid in the beaker is Water. Question: How does density tell you whether an object will sink or float? 1. Calculate: Density is the amount of mass contained in a given volume. To find the density of an object, divide its mass by its volume. Density is recorded in units of grams per cubic centimeter (g / c * m ^ 3) What is the density of an object with a mass of 100 g and a volume of 50 cm³? 2 g/cm³ 2. Record data: In the Gizmo, find mass and volume of the objects listed below. Then calculate each object's density and record it. Finally, test whether each one sinks or floats in water. Object Density (g / c * m ^ 3) Sink or Float? float Chess piece 0.5 Rock 4.0 sink Toy soldier 1.5 sink Apple 0.75 float 3. Draw conclusion: The density of water is 1.0 g/mL, or 1g / c * m ^ 3 Look at the data in your table. How can you use the density of an object to predict it will sink or float? An object will sink in water if it has a density greater than 1g / c * m ^ 3 equal to the density of water). It will float if it has a density less than 1g / c * m ^ 3 4. Apply: In the Gizmo, either Crown 1 or Crown 2 is solid gold (but not both). Find the density of the gold nugget and of each crown. (Hint: You will probably need a calculator to do this.) Crown 1 A. Density of the gold nugget: 579 g + 30c * m ^ 5 = 19.3g / c * m ^ 3 B. Density of Crown 1: 840g + 100c * m ^ 3 = 8.4g / c * m ^ 3 C. Density of Crown 2: 1930g / 100 * c * m ^ 3 = 19.3g / c * m ^ 3 D. Which crown is pure gold? Crown 2 has the same density as the gold nugget, so it must be the one that is pure gold. Crown 1 is not nearly as dense as pure gold.