Matter and Measurement Mrs. Alvarez 9/2013

 Definition: Mass per unit volume of a substance  Formula: D = m/V ; units: g/mL, g/cm 3, kg/L

 Sample Problem A piece of copper has a mass of g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).  Strategy  1. Get dimensions in common units. m = g L = 9.36 cm W = 7.23 cm Thickness (Height) = 0.95 mm = cm  2. Calculate volume in cubic centimeters. V = L x W x H = (9.36 cm)(7.23 cm)(0.095 cm) =  3. Calculate the density. D = m/V Be sure to check sig figs

 2. Use of density as a conversion factor:

Sample Problem: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 95 mL of Hg in grams? In pounds?  First, note that 1 cm 3 = 1 mL  Strategy 1.Use density as a conversion factor to calculate mass (g) from volume. 2.Convert mass (g) to mass (lb) Need to know conversion factor; 454 g = 1 lb

 Density of water changes with temperature – why?

 Intensive property - is a physical property of matter that does not depend on the system size or the amount of material in the system  Examples: density, color hardness, melting point, boiling point  Extensive property – any property that depends on the size of the system. A property that changes as the amount of matter changes.  Examples: mass, volume, temperature, energy released/absorbed

 State of matter: gas, liquid, solid  Kinetic Molecular Theory: A theory of the behavior of matter at the molecular level  Kinetic Energy: The energy of a moving object, dependent on its mass and velocity  K.E. = 1/2mv 2

 Matter has both  Macroscopic –measurable and observable to the naked eye  Macroscopic properties - color, length  Submicroscopic or particulate –not measurable with a microscope  Particle size, chemical bond length

 3 examples  2 forms of energy  Is energy a form of matter  Symbolic level

 Measurement System – in summer work ◦ Length base unit – meter  Conversions: 2.54 cm = 1 inch ◦ Mass base unit – kilogram  Conversions: g = 1 pound (only on earth!) ◦ Time base unit – second  Conversions: 1 hour = 60 minutes;  1 minute= 60 seconds (NOTE THESE ARE EXACT NUMBERS)

 We did this - you tell me! ◦ Volume –

 A problem solving method – ◦ Example: how many seconds in a day ?? ◦ 1 day 24 hours 60 min 60 sec = 1 day 1 hour 1 min

 Find the surface area of a room 20 feet by 12 feet in square meters. ( Use 2.54 cm = 1 inch)

 Using density as a conversion – What is the mass of a gold cube with 2 inch sides? (density of gold =19.3 g/cm 3 )  Hint: need volume in cubic centimeters -

 Accurate – close to the true value  Precision – reproducibility of the measurement  Percent Error:

 State the problem ◦ Organize the information ◦ Determine what you know & what you need to know  Determine the strategy ◦ May stem from prior knowledge  Write down each step ◦ NO WORK NO CREDIT!!  Check your answer ◦ Is it reasonable????

 Chapter 1 ◦ Density p. 39 # 21, 23, 25, 55, 57 ◦ Unit Conversions p , 33, 35, 37, 53, 59 ◦ Problem solving p , 47, 49, 61, 63, 77 ◦ Dimensional Analysis Worksheets ◦ Sig fig review worksheet