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 State Shape and Volume Distance Between Molecules EntropyMotion SOLID Definite shape and volume Closely packed Organized No random motion (vibrating in place) LIQUID Indefinite shape but definite volume Close but free to move Much disorder Some random motion (flowing) GAS Indefinite shape and volume Very far apartMost disorder Completely random motion (diffusion)

Learning Check List examples of physical and chemical properties. NO 2 : 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