Unit Review 3 Key

Grade 8 Science Module 1 Self-Test, Answer Key 87 Module 1 Self-Test Answer Key . fluid . non-fluid fluid o TP . testable question . variables independent variable . dependent variable hypothesis fair test . controlled variable R0 o0 TP . observations conclusion e Comparing Flow Rates 3. a. larger diameter b. +5°C c. smooth Density 4. Density= —2888_ _ 00 __ 4605 o/, - DOV = yolume T 100 mL T g/m ., _mass _20g 3 5. Density = volume = 10 em® = 2 g(cm 0.0Y . mass 6g : 6. Density = volume = 15cm3 = /4’ g/cms 7. Object B would sink because with a density of 2 g/cm3 it has a density greater than water (1.0g/ml). Object C would float because its density is less than that of water. Note: 1 mL =1 cm3 8. Object D would have a greater density because there are more particles (greater mass) in the same space (volume). 9. 60 mL — 50 mL = 10 mL volume 3 mass 20 volume = 10 mL Density = =2 g/mL

88 Module 1 Self-Test, Answer Key Grade 8 Science 10. a. The denser a fluid, the more buoyant force it exerts. b. A hydrometer placed in a less dense liquid (e.g., water) will float lower than one placed in a more dense liquid (e.g., oil). 11. Large boats of steel float even though steel has a higher density than water because large boats contain a large amount of air, and air is less dense than water. When you average the density of the air and the density of steel it is less than water’s density, and therefore allows the boat to float. 12. Liquid B JL Liquid A Liquid C Calculations: Liquid A mass: 20g-15g =5 g density: 5g/20mL = .25g/mL IN THE MIDDLE Liquid B mass: 17g-15g = 2g density: 2g/20mL = .1g/mL. LEAST DENSE Liquid C mass: 25g—15g=10g density: 10g/20mL = .5g/ml. MOST DENSE 13. The particles are situated close together in the bar of gold. The particles in the melted gold should be farther apart, slightly spread out. a. gold bar — solid, melted gold — liquid a. heat energy b. the melted gold is less dense 14. The particles in Balloon B should be spread far apart from each other. The particles in Balloon A are closer together and because of this, more dense. The same particles pictured in Balloon B are spread over a larger area. The density of the air in Balloon B is therefore less.

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