What is Chemistry?

Studying Matter and Measurement

Why Study Chemistry?

The Study of Chemistry

What is chemistry?– Scientific study of matter, its properties, and its

interactions with other matter and with energy

What is matter?– Stuff that has mass– Stuff that occupies space

Scientific Method

Classification of Matter

Elements

Fundamental substances H is 75% of the mass of the universe O, Si are 75% of the earth’s crust O, C, H are more than 90% of the human

body

Relative Abundances

Physical vs. Chemical Changes

Characteristics that can be observed without altering the identity of the substance

Examples: volume, mass, color, malleability, ductility, conductivity, solubility, etc.

Characteristics that cannot be observed without altering the identity of the substance

Examples: flammability, tendency to corrode, reactivity, etc.

Signs of Chemical Change

Energy change Color change Odor change Bubbles forming Precipitate forming

Physical or Chemical Change?

Ice melting Paper burning Cake baking Salt dissolving in water

States of Matter

More on States of Matter

StateShape and

Volume

Distance Between

MoleculesEntropy Motion

SOLIDDefinite shape

and volumeClosely packed

Organized

No random motion

(vibrating in place)

LIQUID

Indefinite shape but

definite volume

Close but free to move

Much disorderSome random

motion (flowing)

GASIndefinite

shape and volume

Very far apart Most disorderCompletely

random motion (diffusion)

Learning Check

List examples of physical and chemical properties.

NO2: What do you see? What phase does this represent? What phase changes are possible.

Qualitative vs. Quantitative

Qualitative measurements involve descriptions

– Ex. I have orange soda.

Quantitative measurements involve numbers.

– I have 2 cans of soda

Uncertainty in Measurement

What is the difference between precision and accuracy? What is shown in each picture?

Another Learning Check

The true temperature outside is 71.2°F. Several thermometers made by one manufacturer record the temperature as 67.8, 68.2, 67.2, 67.6, and 68.0°F.

Are these qualitative or quantitative measurements?

How would you describe this data in terms of accuracy and precision? Why?

Any questions?

“The art and science of asking questions is the source of all knowledge.”

Thomas Berger