Chemistry Overview

• Chemistry = The study of matter and how it changes

• Matter = anything that has mass and occupies space

Matter Not Matter

Categorizing Matter

Stuff

Matter Energy

Mixture Pure substance

Heterogeneous mixture

Homogeneous mixture

compound Element

2-1 What is Matter?

Matter

- made of atoms – the smallest particles that have the properties of an element.

-The properties and characteristics of matter all depend upon what atoms the matter is made of.

Classifying MatterPure Substances – has a constant

composition

1. Elements – made of only one type of atom

- cannot be separated by ordinary chemical or physical means

- ex: iron (Fe), copper (Cu), aluminum (Al)

2. Compound – made of two or more elements in set proportions

- ex: water (H20), salt (NaCl)

Note: A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds. Oxygen gas (O2) is a molecule, but not a compound.

Chemical Formulas

- C16H10N2O2 is the formula for a molecule of indigo, a dye

- It has 16 carbon atoms, 10 hydrogen atoms, 2 nitrogen atoms, and 2 oxygen atoms

- If a number appears before the formula, 6 C6H12O6 it means there are 6 molecules of glucose

Mixtures – blend of pure substances

- 2 or more combined substances in no definite amounts

- each substance keeps its original properties

1. Heterogeneous mixture

- “hetero” means different… mixture is different

- ex: trail mix, salad

2. Homogenous mixture

- “homo” means the same… mixture is the same throughout

- ex: salt water, tea

Liquid Mixtures

Miscible – gasoline is made of more than 100 compounds dissolved

Immiscible – oil and water do not mix together well

Note: gases can mix with liquids – carbonated drinks - homogeneous

States of Matter

There are three basic components or parts to each state of matter that can vary:

1. Temperature

2. Closeness of particles

3. Energy of particles (E)

These components are closely related. Think about how the kinetic theory explains the relationships.

“Most matter found naturally on Earth is either a solid, a liquid, or a gas, but matter also exists in other states” (p46).

Plasma

– free electrons and ions of element; electrically charged gas

Temperature – higher than gases

Particle closeness – far apart; little or no order

Energy – High energy

Examples – fluorescent light bulb, neon signs, stars, lightning, plasma TV screens

Gases

Temperature

• Above the boiling point of the substance

• Steam burns are worse than water burns because boiling water = 100°C where steam can be 125°C

Particle Closeness

• With available space, gas particles spread apart as more Energy is added

• Distance between particles allows for a lot of movement

Energy Level

• Higher E level than liquid or solid

• Requires a lot of E to

evaporate heat

Other

• Gases take the shape of their containers.

• Gases exert pressure on closed containers

• Molecules of gas moving fast in balloon constantly hitting each other and sides of balloon.

Liquids

Temperature

• Between freezing and boiling points

• Water is liquid from 0°C to 100°C

Particle Closeness

• Particles are close together, but not as attracted to each other as in solid form

• Particles can move independently of each other

Energy Level

• Energy is absorbed or released to form solid or gas

Other• Liquids vary in rate at which they spread• This property is called viscosity• If liquid molecules have a strong attraction to

each other slower spread like molasses• Both liquids and gases can spread, so are called

fluids• Some substances do not have a liquid form at

normal temperature and pressure

Solids

Temperature

• Lower temp to achieve freezing

• Freezing point – melting point

Particle Closeness

• Particles are close allowing almost no movement… particles can vibrate in place

• Organized arrangement because molecules bond

• Solids maintain their own shape

Energy Level

• Lowest E level there is still energy present

• There is never NO energy in a system

Energy’s Role in Phase Changes

Energy is the ability to change or move matter

• Examples: electricity, batteries (stored), candles, food, etc

Phase Changes

• Energy must be added to cause melting or evaporating. The molecules gain E and then move faster. Think of the kinetic theory.

• Energy is transferred from substance to surroundings when condensing and freezing.

Sublimation – change from solid directly to gas

• Dry ice = CO2 solid to smoky gas

• Ice in freezer will sublime and ice gets smaller

• A change in the state of a substance does not change its composition.

Law of Conservation of Mass

Mass cannot be created or destroyed.

• Mass before change = Mass after change

1. Ice melting

• Change of state

• Same mass

• Remember Δ volume ≠ Δ mass

2. Combining 2 liquids no mass is lost

• 20 g + 20 g = 40 g

3. Burning a match

• Mass A = Mass B

• Match = burnt mass + gas

4. Chemical reaction

• XXX + YYY ZZZ

• Reactants Products

• 3 atoms + 10 atoms 13 atoms

• The amount of atoms entering into a reaction will be the amount that come out of the reaction.

Law of Conservation of Energy

Energy cannot be created or destroyed.

• Energy before change = Energy after change

• Energy is stored in many ways = food, gasoline, batteries

1. Heating water provides water molecules with enough energy to evaporate

2. Energy from gasoline and you car drives a certain distance