10.5 Density with Volume.notebook May 01, 2014

Transcription

1 Bellwork: I want you to think about the four things listed below, which one is different from the other three? Why? Tennis Balls in a can Gum Balls in a tube Quarters in a purse Beads on a bracelet

2 10.5 Density of Volume Objective: Define density. Use physical measurements to calculate density. Use density values to calculate mass or volume.

3 Density Lets think about a golf ball and a ping pong ball, they are about the same size. Which is heavier? Now imagine a similar size ball made out of lead. That would be very heavy indeed! What are we comparing? What are we comparing when we say one is heavier than another?

4 Density of an object is a ratio of the mass of the object to the volume of the object. Density is an intensive property. This means that the amount of the sample does not matter when you figure density. A swimming pool has the same density as a glass of water. 1.0 g/ml

5 The SI units of density are kilograms per cubic meter (kg/m3), since the kg and the m are the SI units for mass and length respectively. Most solids and liquids have densities that are conveniently expressed in grams per cubic centimeter (g/cm3). Since a cubic centimeter is equal to a milliliter, density units can also be expressed as g/ml. Gases are much less dense than solids and liquids, so their densities are often reported in g/l. Densities of some common substances at 20 C.

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7 An 18.2 g sample of zinc metal has a volume of 2.55 cm. Calculate the density of zinc. Step 1: List the known quantities and plan the problem. Known mass = volume = Unknown density = We use the density formula, D = m/v. 3

8 Step 2: Calculate

9 Using Density to Determine Mass and Volume 3 1. What is the mass of 2.49 cm of aluminum? 2. What is the volume of 50.0 g of aluminum?

10 Step 1: List the known quantities and plan the problem. Known Density of aluminum = What does question one tell us? What does question two tell us? Unknown Mass of question one = Volume of question two =

11 Step 2: Calculate In problem 1, the mass is equal to the density multiplied by the volume. In problem 2, the volume is equal to the mass divided by the density.

12 British Thermal Units (BTUs) A BTU, or British Thermal Unit, is as basic measure of thermal (heat) energy. BTUs are often used in the United States to "rate the heat output of fuels and appliances". Human beings also put out heat.

13 Eighty seven middle school students danced their hearts out at the middle school dance last night, each producing an unprecedented 3,000 BTUs of heat while listening to the amazing music of One Direction, Taylor Swift and M.C. Hammer (M.C. Who?). The dance was held in the multipurpose room which is 110 feet long, 80 feet wide, and 35 feet tall. To the nearest thousandth, how many BTUs per cubic foot did they produce? We are given the BTUs produced by each student so our first step is to find the total amount of heat:

14 Next we need to find the volume of the multi purpose room: This is the volume, or the total cubic feet of the room. To find the BTUs per cubic foot, or density, you divide mass by the volume:

15 Neil Glennbuzz, astronaut extraordinaire, has returned to the Kennedy Space Center with samples from his recent interplanetary travels. He has 3.47 kilograms of soil from Mars. Given that Mars has an average soil density of 3.93 g/cm 3, how many cubic centimeters of soil is that?

16 A balloon archway has been ordered for decorating the prom this weekend. The archway will contain 375 balloons, each holding 1.5 liters of helium. Each balloon has a mass of 15 milligrams when empty, and all the string and fixings that hold the balloons together total another 65 grams. If helium has a density of grams per liter, what is the mass of the entire archway?