Chemistry Chapter 1

Where does chemistry come from?

COMES FROM GOD (help us understand God’s creation)

What is the central science?

Chemistry (basis for many other sciences)

What is important to know about chemicals?

There are chemicals that can both help and hurt us, it’s important to understand both. (Remember Alex (; )

Chemistry Definition

The study of matter, its properties, its properties, and the changes that matter undergoes.

Matter Definition

The physical material of the universe; anything that has mass and occupies space.

Property Definition

Any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types.

Element Definition

A substance that cannot be decomposed into simpler substances. (only made of one type of atom)

Atoms Definition

The smallest representative particle of an element. The almost infinitesimally small building blocks of matter. (each element is composed of a unique kind of atom)

Molecule Definition

A chemical combination of two or more atoms.

Matter Definition

The physical material of the universe; anything that has mass and occupies space.

What are the two ways to characterize matter?

Physical state and composition

States of Matter: Solid

Definite shape and a definite volume; not easily compressed

States of Matter: Liquid

Distinct volume independent of its container, assumes the shape of the portion of the container it occupies; not easily compressed.

States of Matter: Gas (vapor)

No fixed volume or shape and it uniformly fills its container; can be compressed to occupy a smaller volume or expand to occupy a larger one.

What can convert states of matter?

Changes in temperature and/or pressure.

What would happen if ice didn’t float?

Ice would freeze from the bottom up, killing organisms.

Pure Substance Definition

Matter with fixed composition and distinct properties. (all are either elements or compounds)

Compound Definition

A substance composed of two or more elements.

Mixture Definition

A combination of two or more substances where each substance retains its chemical identity.

How many known elements are there?

118 (vary widely in abundance)

What are the two most abundant in the Milky Way?

Hydrogen (74%) and Helium (24%)

What five elements make up over 90% of the Earth’s crust?

Oxygen, silicon, aluminum, iron, and calcium.

What three elements make up over 90% of the human body?

Oxygen, carbon, and hydrogen.

What happens when elements interact with each other?

They form compounds.

How are compounds different from the elements that make them up?

They have different properties.

Law of Constant Composition/Law of Definite Proportions

Compounds have a definite composition. The relative number of atoms of each element in the compound is the same in any sample.

Heterogeneous Mixture

Vary in compositions throughout a sample.

Homogeneous mixture

Same composition throughout sample.

Properties of Matter: Physical

the properties that can be observed or measured without changing the composition of a substance.

Properties of Matter: Chemical

the properties that describe the way a substance may change or react to form other substances.

Properties of Matter: Intensive

A property that DOESN’T depend on the amount of sample being examined. (density, boiling point, color)

Properties of Matter: Extensive

A property that DOES depend on amount of the sample examined.

Physical change

changes in physical appearance only (NO chemical composition)

Chemical Change

transformed chemically into a different substance.

Separation of Mixtures: Filtration

Solid filtered out from a liquid.

Separation of Mixtures: Distillation

Uses differences in boiling points to separate a liquid homogeneous mixture.

Separation of Mixtures: Chromatography

Separates substances based on differences to adhere to the solid surface.

Energy Definition

The capacity to do work or transfer heat.

Work Definition

The energy transferred when a force exerted on an object causes a displacement of that object.

Heat Definition

The energy transferred to cause the temperature of an object to increase.

Work Equation

w = F x d

Potential Energy

Stored energy; depends on relative position of an object compared to other objects. (Further from gravity = higher potential)

Kinetic Energy

The energy of motion (more mass and/or velocity = more kinetic)

Kinetic Energy Equation

Ek = 1/2mv^2

Transfer of heat… (energy)

The transfer of kinetic energy at a molecular level.

Electrostatic potential energy definition

Stored energy of charged particles based on their positions relative to each other. (increases as magnitudes/distance between increases)

Quantitative Definition

Relating to, measuring, or measured by the quantity of something.

SI Unit: Length

Meter (m)

SI Unit: Mass

Kilogram (kg)

SI Unit: Temperature

Kelvin (K)

SI Unit: Time

Second (s or sec)

SI Unit: Amount of Substance

Mole (mol)

SI Unit: Electric current

Ampere (A or amp)

SI Unit: Luminous intensity

Candela (cd)

Kilo

(k) 10³

Deci

(d) 10^-1

Centi

(c) 10^-2

Milli

(m) 10^-3

Micro

(μ^b) 10^-6

Nano

(n) 10^-9

Where does heat flow?

From a substance at higher temp to a substance of lower temp

What is the same about Kelvin and Celsius?

The size of a degree is the same.

Most common metric units for volume?

L and mL

Density Definition

The amount of mass in a unit volume of a substance/ physical property

Do substances change volume when they are heated or cooled?

Yes

If no temperature is reported, what do you assume it is?

25 degrees Celsius

Calorie vs. calorie

1 Calorie (nutritional) = 1 kcal (1000 claories)

Exact Number

The value is known (12 apples)

Inexact Numbers

The value has uncertainty (measurements)

Precision

The closeness of agreement among several measurements of same quantity.

Accuracy

A measure of how closely individual measurements agree with the “true” value

Are all nonzero digits significant?

Yes

Are zeros between nonzero digits significant?

Yes

Are zeros at the beginning of a number significant?

No

Are zeros at the end of a number significant?

Only if it contains a decimal point.

Addition and subtraction sig fig rules

same number of decimal points as the measurement with the FEWEST decimal places.