AP ChemistryPreface and Chapter

1Matter and Measurement

Mrs. Hallman9/2013

Definition: Mass per unit volume of a substance

Formula: D = m/V ; units: g/mL, g/cm3, kg/L

Density

Sample Problem A piece of copper has a mass of 57.54 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 = 57.54 gL = 9.36 cmW = 7.23 cmThickness (Height) = 0.95 mm = 0.095 cm 2. Calculate volume in cubic centimeters.

V = LxWxH = (9.36 cm)(7.23 cm)(0.095 cm) =

3. Calculate the density. D = m/V Be sure to check sig figs

Sample Problem

Sample Problem: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?

First, note that 1 cm3 = 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 as a conversion factor

Density of water changes with temperature – why?

A last thought on density

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

Extensive & Intensive Properties

Temperature Discussion

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. = 1/2mv2

Classification of Matter

Solid - Liquid - Gas

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

Matter at the Macroscopic and Particulate Levels

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

Matter Q’s

Measurement System – in summer work

◦ Length base unit – meter Conversions: 2.54 cm = 1 inch

◦ Mass base unit – kilogram Conversions: 453.5 g = 1 pound (only on earth!)

◦ Time base unit – second Conversions: 1 hour = 60 minutes;

1 minute= 60 seconds (NOTE THESE ARE EXACT NUMBERS)

Units of Measurement

We did this - you tell me!

◦ Volume –

Derived units

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

Dimensional Analysis -1

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

Dimensional Analysis-2

Using density as a conversion – What is the mass of a gold cube with 2 inch sides? (density of gold =19.3 g/cm3)

Hint: need volume in cubic centimeters -

Dimensional Analysis -3

Accurate – close to the true value Precision – reproducibility of the

measurement

Percent Error:

Accuracy vs. Precision

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????

Problem Solving

Chapter 1◦ Density p. 39 # 21, 23, 25, 55, 57◦ Unit Conversions p. 40 31, 33, 35, 37, 53, 59◦ Problem solving p. 40 45, 47, 49, 61, 63, 77◦ Dimensional Analysis Worksheets◦ Sig fig review worksheet

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