What is Chemistry?Chapter 1

Scientific MethodObservations

Hypothesis

Experiment

Results

Revise(if necessary)

Conclusions

The Method in Action

• Science is a methodology • It is systematic and objective. • The goal of all science is to understand – • To codify the laws of nature = What?• And to construct models of how nature works

(to explain it) = How/Why?

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LawTheory

Prediction

Experiment

Theory modified

Extending the Method

Experiment

Observations

Hypothesis

It’s Just a Theory…• Theory – A model that provides an overall

explanation that agrees with observed behaviors.• e.g. Newton’s Theory of Gravity• Scientific Law – A summary of observed

(measureable) behavior.• e.g. Newton’s 1st Law of Motion• When a model is labeled a theory, in science, it

is as close to being proven as humanly possible.

What is Chemistry?

• The study of Matter.• Specifically, it is the study of • Chemicals, • Their properties and behaviors, • And the changes they undergo.

What is a Chemical?

• A substance that has a definite Composition (it’s always the same).• For example, Water is H2O• It’s the same here in Moorestown as it is in

California – still the same stuff on Mars

In The Beginning…

• The universe can be divided up into two categories: matter and energy. • Matter is defined as anything that has mass and

takes up space. • Matter is the stuff we think of when we think of stuff.

• Energy is most easily described as light and heat,

though the formal definition is: • “The capacity to do work.”

What is Mass?

• Mass is a fundamental property. • It is a measure of the amount of matter in an object. • It is measured in kilograms (kg) or grams (g). • 453.59 grams are in 1 pound (mass). • 2.2046 pounds (mass) are in 1 kilogram.

What is Volume?

• Volume is a measure of the size of an object or region in 3-D space. • Volume has cubic units – basically l*w*h.• It is typically measured in liters (L). • 1,000 cubic centimeters (cm3) = 1 Liter• That’s equivalent to a cube 10 cm per side.• There are 3.785 liters in 1 gallon.

Mass & Weight

• Weight is a measure of the gravitational force exerted on an object. • It is measured in Newtons (N). • There are 4.448 Newtons in 1 pound (force). • On the surface of the Earth, 1 pound (mass) is equal

to 1 pound (force).

Properties of Matter

• Matter can be identified by its properties. • There are two main types: #1 Intensive Properties are those that do not change. • They are always the same, regardless of the amount

of substance present. • They are also called Characteristic properties because

they can be used to identify the substance.

Common intensive Properties

• Boiling & freezing points,• Density• Color• Hardness• Crystal structure• Conductivity, &• Reactivity.

Extensive Properties

#2 Extensive Properties depend on the amount of substance present. • They vary from sample to sample and cannot be used

to identify substances. • Common Extensive Properties are: length, mass,

weight, & volume.

Characterization

• Many Intensive properties are qualitative. • Qualitative properties are characteristics that

cannot be measured. • When qualitative properties are noted, the

quality of the substance is described. • Some examples are color, luster, reactivity, &

conductivity.

Characterization w/ Numbers

• Extensive & some Intensive properties are quantitative.

• Quantitative properties are characteristics that have to be measured.

• When quantitative properties are noted, the quantity of the substance is described.

• All quantitative properties must have a number and a unit.

• Numbers without units are meaningless. • ALWAYS REMEMBER THE UNITS!!!

Quantitatively Speaking

• Some quantitative properties are measured directly using some tool.

• They are called direct measurements and carry the units of the tool.

• For example, measuring the length of a piece of steel with a ruler will give you a quantitative property, length, with centimeters (or inches) as the unit.

Indirection

• Some characteristics cannot be measured directly.

• They must be calculated from other direct measurements.

• Properties like this are called derived measurements.

• Derived measurements include the units of each measurement used to derive them.

Derived Properties

• For example, the volume of a cube must be calculated.

• If a side of a cube measures 4 cm, then the volume is:

• 4 x 4 x 4 = 64• cm x cm x cm = cm3

• volume = 64 cm3

Another One

• Speed is another derived quantitative property. • It is calculated using distance traveled per unit of

time. (s = d ÷ t)• For example, if a ball rolls 24 meters in 5

seconds, its speed is • 24 m ÷ 5 s: • 24 / 5 = 4.8• m ÷ s = m/s• Speed = 4.8 m/s

Intensive from Extensive

• Some intensive properties can be derived from extensive properties.

• Density is a quantitative intensive property that is derived from two quantitative extensive properties: mass and volume.

• But more on that later…

Property Value Intensive/Extensive Quant/Qual Direct/Derived

1 Length 8.76 cm

2 Color Purple

3 Weight 3.2 kg

4 Density 1.02 g/mL

5 Pressure 14.7 psi

6 Temperature 98.6°F

7 Luster Metallic/Shiny

8 Melting Point 16.2°C

9 Force 48.1 kg•m/s2

10 Color Green (532 nm)

11 Speed 758 m/s

12 Reactivity Reacts w/ Water

13 Volume 143.2 mL

14 Crystal Type Face-centered

Property Value Intensive/Extensive Quant/Qual Direct/Derived

1 Length 8.76 cm Extensive Quantitative Direct

2 Color Purple Intensive Qualitative n/a

3 Weight 3.2 kg Extensive Quantitative Direct

4 Density 1.02 g/mL Intensive Quantitative Derived

5 Pressure 14.7 psi Extensive Quantitative Derived

6 Temperature 98.6°F Extensive Quantitative Direct

7 Luster Metallic/Shiny Intensive Qualitative n/a

8 Melting Point 16.2°C Intensive Quantitative Direct

9 Force 48.1 kg•m/s2 Extensive Quantitative Derived

10 Color Green (532 nm) Intensive Quantitative Direct

11 Speed 758 m/s Extensive Quantitative Derived

12 Reactivity Reacts w/ Water Intensive Qualitative n/a

13 Volume 143.2 mL Extensive Quantitative Direct or Derived

14 Crystal Type Face-centered Intensive Qualitative n/a