DENSITY CALCULATIONS

Transcription

1 PRACTICE Name: Date: Class: DENSITY CALCULATIONS Density is a measure of how much matter exists within a given volume. The mass of an object tells you how many atoms exist within a certain substance (amount of matter). Volume is expressed in ml or cm 3 and is the quantity of three-dimensional space occupied by a liquid, solid, or gas. Liquid volumes are usually expressed in ml or L while solid volumes are usually expressed in cm 3 or m 3. It is important to remember that 1 cm 3 is equivalent to 1 ml. The equation for density is mass volume and the unit is usually g/ml or g/cm 3. Density can have other units, but it is always a unit of mass divided by a unit of volume. Blocks A and B have the same volume, but different masses. Block A Density: Block B Density: Block A is more dense than Block B. Using your knowledge of significant digits, perform the following calculations using the format explained below. Circle your final rounded answer and don t forget about units! Example #1: Mass = 4.25g Volume = 12.4 ml Density =? 1

2 Practice: 1. Mass = g Volume = 10.1 ml Density =? 2. Mass = 45.9 g Volume = 100 ml Density =? 3. Mass = 0.98 g Volume = 1 ml Density =? 4. Mass = g Volume = 4.55 ml Density =? 5. Mass = 11.0g Volume = 5.67 cm 3 Density =? 2

3 Find the density of each block. Which block is more dense? List of Information: Block C Equation: Calculation: List of Information: Block D Equation: Calculation: Find the density of each block. Which block is more dense? List of Information: Block E Equation: Calculation: List of Information: Block F Equation: Calculation: 3

4 Find the density of each block. Which block is more dense? List of Information: Block G Equation: Calculation: List of Information: Block H Equation: Calculation: Density is a physical property. A physical property is defined as a characteristic of matter that may be observed and measured without changing the chemical identity of a sample. Density can be used to identify unknown substances. 4

5 Four graduated cylinders filled with different liquid samples were measured on a digital balance. The mass readings below each cylinder reflect the mass of each filled cylinder. Each cylinder has a mass of 5.00 g. Calculate the density of each liquid. Then, identify the liquid present in each sample. SUBSTANCE DENSITY (g/ml) PROPERTIES, USES Ethylene glycol Toxic; the major component of automobile antifreeze Present in Cylinders? If yes, which one? Water Methanol Toxic; gasoline additive to prevent gas line freezing Acetic acid Component of vinegar Glycerol Solvent used in home care products 5

6 Molecules can be packed in close together like in a rock or more spread out like in bubble wrap. The positioning of molecules affects the density of an object. Objects with tightly packed molecules are more dense than those where the molecules are spread out. Density is a large part of why things float while other things do not. Objects like stones, coins, and marbles are denser than water these objects will sink in water. Objects like apples, wood, and ice are less dense than water these objects will float in water. Objects that are filled with air like balloons, empty bottles, boats and footballs will also float because air is less dense than water. Shape also plays a role in determining if an object will float or not. Water has a density of 1 g/ml. Oil is less dense than water, so it will float while corn syrup is denser than water, so it will form a layer below. Pasta will settle between the water and corn syrup because it is dense than water, but less dense than corn syrup. In the graduated cylinder below, draw and label the expected positioning of liquids if they were carefully layered in order of density. SUBSTANCE DENSITY (g/ml) Dark Karo syrup 1.37 Water 1.00 Glycerin 1.26 Vegetable oil 0.91 Isopropanol 0.87 Honey 1.37 Baby oil 0.82 Dawn Dish washing liquid 1.03 Light Karo syrup 1.33 Lamp oil 0.80 References and Additional Resources:

7 Density of H2O The water molecule is asymmetrical and is therefore oppositely charged at its two ends. This is called a dipole. It thus behaves differently from other substances in many ways. Ice is less dense and floats on the surface. Freshwater has its greatest density at four degrees, and sinks to the bottom. This is then overlain by warm water. Salty water has different characteristics. 7