Chapter 1

Chemistry – Chemistry – the study of all substances and the changes they can undergo. the study of all substances and the changes they can undergo. Scientific Method- Observation Observation Stating a Question Stating a Question Hypothesis – possible answer Hypothesis – possible answer Experiment Experiment Conclusion – what you found in your experiment Conclusion – what you found in your experiment

Scientific method leads to Scientific method leads to Natural Law – Tells you how nature behaves but not why it behaves. Natural Law – Tells you how nature behaves but not why it behaves. Finally you form a Finally you form a Theory – Explains why nature behaves in the way described by natural law. Theory – Explains why nature behaves in the way described by natural law. Used for prediction of results for further experiments. Used for prediction of results for further experiments.

During the experiment… During the experiment… Experimental Control - Factor that remains constant during the experiment. It is compared with the variable. Experimental Control - Factor that remains constant during the experiment. It is compared with the variable. Variable - Factor that is being tested during the experiment. Variable - Factor that is being tested during the experiment.

Measurement… Measurement… When we perform experiments, we need to use some form of measurement. When we perform experiments, we need to use some form of measurement. Metric System – International set of units (SI) Metric System – International set of units (SI)

Base units- Base units- Mass = kilogram (kg) Mass = kilogram (kg) Length = meter (m) Length = meter (m) Time = seconds (s) Time = seconds (s) Count, quantity = mole (mol) Count, quantity = mole (mol) Temperature = Kelvin (K) Temperature = Kelvin (K) Electric Current = ampere (A) Electric Current = ampere (A) Luminous intensity = candela (cd) Luminous intensity = candela (cd)

Derived Units – made from combining 2 or more base units. Derived Units – made from combining 2 or more base units. Ex. Area = length x width = m 2 Ex. Area = length x width = m 2 Volume = length x width x height = cm 3 Volume = length x width x height = cm 3 Density = mass / volume = g/cm 3 Density = mass / volume = g/cm 3

Exceptions to SI units… Exceptions to SI units… Volume = liter (L) Volume = liter (L) Pressure = atmosphere millimeter of Hg (atm mm Hg) Pressure = atmosphere millimeter of Hg (atm mm Hg) Aka Pascal Aka Pascal Temperature = Celsius degree (C o ) Temperature = Celsius degree (C o ) Energy = Calorie (cal) Energy = Calorie (cal)

Reliability in Measurement Reliability in Measurement Accuracy vs. Precision Accuracy vs. Precision Precision – Measurement that gives the same result again and again under the same conditions Precision – Measurement that gives the same result again and again under the same conditions Accuracy – Measurement that is close to the accepted value. Accuracy – Measurement that is close to the accepted value.

Significant Digits – Defined as certain digits and the estimated digit of a measurement. Significant Digits – Defined as certain digits and the estimated digit of a measurement. Rules for determining sig. Digs. Rules for determining sig. Digs. “0”s as placeholders are NOT significant! “0”s as placeholders are NOT significant! Ex g or m Ex g or m

Atlantic – Pacific Rule Atlantic – Pacific Rule If the decimal is Present, count from the Pacific side (left) beginning with the first non-zero digit If the decimal is Present, count from the Pacific side (left) beginning with the first non-zero digit If the decimal is Absent, count from the Atlantic side beginning with the first non-zero digit. If the decimal is Absent, count from the Atlantic side beginning with the first non-zero digit.

How many significant Digits are present? How many significant Digits are present? 1700 cm 1700 cm kg kg L L mg mg m m

How many sig. digs. are present? How many sig. digs. are present? mL mL dg dg 6.60 x mL 6.60 x mL 2.00 x 10 3 g 2.00 x 10 3 g x 10 4 L x 10 4 L

Calculation rules for Sig. Digs. Calculation rules for Sig. Digs. Multiplication and Division Multiplication and Division The measurement with the SMALLEST NUMBER OF SIG. DIGS. Determines how many digits are allowed in the answer. The measurement with the SMALLEST NUMBER OF SIG. DIGS. Determines how many digits are allowed in the answer. Ex. 4.3 x 6.45 will have 2 sig. digs. in the answer. Ex. 4.3 x 6.45 will have 2 sig. digs. in the answer = = 28

Addition and Subtraction Addition and Subtraction The number of significant digits is dependent upon or rounded off to the measurement with the largest uncertainty. ***Use the least amount of decimal spots*** The number of significant digits is dependent upon or rounded off to the measurement with the largest uncertainty. ***Use the least amount of decimal spots*** Ex = Ex = rounded to rounded to 13.4

Scientific Notation Scientific Notation Why use it? Why use it? Distance from the sun = 93,000,000 miles Distance from the sun = 93,000,000 miles Al strip = 4.12 g contains 1.2 x atoms Al strip = 4.12 g contains 1.2 x atoms

Rules for Scientific Notation Rules for Scientific Notation Express the same number of significant digits Express the same number of significant digits Keep one digit to the left of the decimal point Keep one digit to the left of the decimal point Multiplication and Division, add the number of exponents Multiplication and Division, add the number of exponents

Simplify the following: Simplify the following: (4.2 x 10 6 )(1.1 x ) (4.2 x 10 6 )(1.1 x ) 2.3 x 10 2 (5.0 x 10 5 )(1.2 x 10 1 ) (5.0 x 10 5 )(1.2 x 10 1 ) 9.0 x 10 10

2.0 x 10^2 2.0 x 10^2 6.7 x 10^ x 10^-5

Factor-Label Method/ Dimensional Analysis Factor-Label Method/ Dimensional Analysis Problem Solving Method Problem Solving Method Treat units as factors, which can be cancelled Treat units as factors, which can be cancelled Must know your equalities/conversion factors Must know your equalities/conversion factors Choose the equality that cancels out the original unit Choose the equality that cancels out the original unit

Steps: Steps: 1) Begin with known 1) Begin with known 2) Decide upon equality (write this near the problem) 2) Decide upon equality (write this near the problem) 3) Arrange units to cancel out original 3) Arrange units to cancel out original 4) Do the math! 4) Do the math!

How many seconds are in 4 hours? How many seconds are in 4 hours? How many kilograms are in 5 g? How many kilograms are in 5 g? Change 286 cg to Mg. Change 286 cg to Mg.

To change from English to Metric units, use chart on page 38. To change from English to Metric units, use chart on page 38. How many inches are in 354 cm? How many inches are in 354 cm?

Ratios – common method of expressing results and/or measurement in chemistry Ratios – common method of expressing results and/or measurement in chemistry Similar to a fraction Similar to a fraction Units in numerator and denominator Units in numerator and denominator

Ex. Ex. Speed = mph Speed = mph Lunchmeat = dollars/lb Lunchmeat = dollars/lb Density = g/cm 3 or g/mL Density = g/cm 3 or g/mL Population Density = people/km 2 Population Density = people/km 2 Pressure = psi or p/in 2 Pressure = psi or p/in 2

Most substances-Solid forms sink in its own liquid because solid form is more dense. Most substances-Solid forms sink in its own liquid because solid form is more dense. EXCEPTION- Water. EXCEPTION- Water. The freezing point of water is 0 degrees C. The freezing point of water is 0 degrees C. Solid ice floats in liquid water. Solid ice floats in liquid water. Water is most dense at 4 degrees C. Water is most dense at 4 degrees C.

What would happen if ice did not float to… What would happen if ice did not float to… The ocean? The ocean? It would freeze It would freeze The earth’s temperature? The earth’s temperature? It would decrease It would decrease

The icebergs? The icebergs? They would sink and never melt They would sink and never melt The earth? The earth? It would freeze It would freeze Life? Life? It would cease to exist It would cease to exist

Solid Density Solid Density Used to find the density of solid objects. Used to find the density of solid objects. Regular geometric shapes vs. irregular shapes. Regular geometric shapes vs. irregular shapes.

Liquid Density Liquid Density The density of water The density of water 4 degrees C 4 degrees C Other fluids have different densities Other fluids have different densities Oil floats on water Oil floats on water Density – mass per unit of volume Density – mass per unit of volume

Ex. Ex. Zinc Cylinder Zinc Cylinder Diameter is 1.22 cm Diameter is 1.22 cm Height = 3.28 cm Height = 3.28 cm Mass = 28.79g Mass = 28.79g

V= ∏r² h V= ∏r² h h= 3.14 x (0.61cm)² x 3.28cm =3.83cm³ h= 3.14 x (0.61cm)² x 3.28cm =3.83cm³ V= 3.83 cm 3 V= 3.83 cm 3 M= g M= g D= m/v = 28.79g/3.83cm³ =7.52g/cm 3 D= m/v = 28.79g/3.83cm³ =7.52g/cm 3