Chemistry: Chemistry & Measurement/ The Nature of Matter

What is chemistry?

The study of matter and the changes it undergoes.

Define matter

Anything that has mass and takes up space.

What is a chemical?

A substance with a definite and constant composition.

What are the steps of the scientific method?

observation, hypothesis, experiment, theory, law

What is a theory?

A well-tested explanation of natural phenomena

What is a scientific law?

A statement that describes a consistent natural relationship or pattern

What are the three states of matter?

Solid, liquid, gas

How does a physical change differ from a chemical change?

Physical change does not alter the identity of the substance, while chemical change forms a new substance

List signs of a chemical change

Color change, gas formation, precipitate, heat/light change.

Define element

A pure substance made of only one type of atom

Define compound

A substance made of two or more laments chemically bonded in a fixed ratio

Define mixture

A physical blend of substances that are not chemically combined

Homogeneous vs. heterogeneous mixture

Homogeneous: uniform composition

Heterogeneous: visibly different parts.

What are SI units used for?

Standard units for measurement in science

SI units: length? mass? temperature?

meter (m); kilogram (kg); kelvin (K)

Hat are significant figures?

Digits in a measurement that reflect the precision of the value

Do leading zeros count as sig figs?

No

When do trailing zeros count as sig figs?

Only when a decimal point is present

Sit fig rule for multiplication/division?

Answer must have the fewest sig figs from the values used

Sig fig rule for addition/subtraction?

Answer must have the fewest decimal places

What is density?

mass per unit volume: D= m/V

What is the density of water?

approximately 1.00 g/mL

Define a physical property

a characteristic observed without changing identity (e.g. color, melting point)

Define a chemical property

ability of a substance to change into another substance (e.g. flammability)

Example of intensive vs extensive property?

Intensive: density (not size-dependent)

Extensive: mass, volume (depends on amount)