Chemistry

• Read Pages x-xiii, and 6-9 in text

• Watch Accident at Jefferson High and fill in the video sheet on pages 6 & 7 of your notes package

• Complete the exercise on page 8 of your notes package

Meaning Symbol Precaution

1 compressed gas A2 flammable B3 oxidizing E4 immediate toxic effects C5 biohazardous G6 other toxic effects D7 corrosive F8 reactive H

Classifying Matter

• Ancient Greek philosophers believed that all matter was composed of four “elements”

1.Earth2.Water3.Fire 4.Air

The Nature Of Matter

• Matter is often described as anything that has a mass and takes up space.

• Matter has Physical properties and

chemical properties .

Physical Properties:

Can be observed without changing the substance into something new (ie: by not changing the chemical formula)Examples of physical properties include….

Colour Shape Freezing point

Size Density Boiling point

Conductivity

Odor solubilityWhen water changes to ice the formula is still H2O.

Changes in state are physical changes!!

• Solids

• Liquids

• Gases

• plasma

Phases of Matter

When matter changes state ( phase) this is a change in physical property or physical change.

• Solids: A solid has a definite shape and definite volume. The shape of the solid dos not depend on the shape of the container. Expand only slightly when heated and are not compressible.

Dames Point Bridge -

 Jacksonville, FL

• Liquids: A liquid has no definite shape but does have a definite volume. Liquids take on the shape of their containers. Liquids expand only slightly when heated and are not compressible.

• Gases: A gas has no definite shape and no definite volume. Gases expand, without limit, to fill any space and are highly compressible.

Fourth State of matter….Plasma

Chemical PropertiesChemical properties are those which describe the way the substance behaves when it reacts to form a new substance.

If the chemical formula of the substance changes, then a chemical reaction has occurred.

reactants products

Video of this reaction

Chemical Properties What are some chemical properties?

Sound Smell Bubbles

Smoke Light Heat

Colour change

Classification of Matter

Matter

•Anything with mass and volume

•May be solid, Liquid, or gas

Mixture

•Combinations of matter that can be separated by physical means

Pure Substance

•Matter that has definite composition

Heterogeneous Mixture (Mechanical Mixture)

•Different components of the mixture are visible

Homogeneous Mixture (Solution)

•Different components are not visible

Mixture

•Combinations of matter that can be separated by physical means

•Do not have definite composition

Pure Substance

•Matter that has definite composition

Element

•Cannot be chemically broken down into simpler substances

Compound

•Two or more elements that are chemically combined

•Can be separated chemically into simpler substances

Elements: Elements are substances composed of only one type of atom.

Pure Substances

Compounds: Compounds are made from two are more different kinds of atoms.

Mixtures• Heterogeneous Mixture: Not

uniform in composition (ie: the individual parts of the mixture can be seen.)

Homogeneous Mixture (solution) A homogeneous mixture has the

same composition throughout. One part is indiscernible from the next.

Problems

Are the following homo or– Ocean water

• Homo

– Cheese• Homo

– Can of garbage• hetero

– Air• Homo & hetero

– Lemonade• homo

hetero mixtures?– Mashed potatoes

• homo

– Aquarium• hetero

– Vanilla Ice-cream• Homo

– Blood• homo

– Milk• homo

Developing Atomic Theories

Atomic Theories• Dalton Dalton’s Atomic Theory

(1766- 1844)

• Atoms are spherical like billiard balls.

•Each atom has it’s own unique properties.

•Atoms are indivisible; they are the smallest units of matter.

•Atoms can combine in many ways to create a wide variety of chemical compounds

In Your Notes•All matter is made up of small particles called atoms.•Atoms cannot be created, destroyed, or divided into smaller particles.•All atoms of the same element are identical in mass and size, but they are different in mass and size from the atoms of other elements.•Compounds are formed when atoms of different elements combine in fixed proportions.•Chemical reactions change the way atoms are grouped, but the atoms themselves are not changed in reactions.

J.J. Thomson(1856-1940)

Just before 1900, scientists began to believe that matter had an electrical charge.

Atoms seemed to have either a positive or a negative charge.

Thomson’s Experiment

• Based on his experiments with cathode ray tubes, Thomson concluded that matter contained tiny, charged particles

J.J. Thomson

(1856 – 1940)

Raisin Bun Model

•Thomson discovers the electron. The electron is 2000X smaller than the smallest atom and has a negative charge. Atoms must contain electrons.

•Electrons must be spread-out evenly throughout a positively charged atom like raisins in a bun.

Why would they spread out evenly?

Rutherford Famous Gold Foil Experiment

•Alpha particles from radioactive polonium are fired at a thin piece of gold foil (roughly 200 atoms thick)

•Most alpha particles pass through the gold undeflected… they should! The experiment is analogous to shooting a cruise missile through some tissue paper!!

(1871-1937)

Animation

• Rutherford proposed that the atom had the following:

• Nucleus: a central region that is positively charged, extremely small and contains almost all the mass of the atom– Rutherford visualized tiny particles in side

the nucleus called Protons each with a single positive charge

• Electrons: particles with a single negative charge located in the outer region of the atom. – Suggested that electrons move around the

nucleus.

Rutherford’s Model•Atoms have a very small nucleus where (almost) all of the mass is located. Since the nucleus is so small, the alpha particles had a very small chance of actually hitting it.

•The nucleus is very dense (1000 trillion times denser than the human body)

If a nucleus was the size of an average human being, the bathroom scale would read: 200 quintillion pounds

•The nucleus is made of protons and neutrons. Protons have a positive charge. Neutrons have no charge. Protons and neutrons are about the same mass, roughly 2000 times more massive than electrons.

Electrons orbit around the outside of the nucleus at relatively great distance, like planets around the sun. Most of the volume occupied by an atom is empty space!!

If a nucleus was the size of your baby fingernail, the nearest electron would be half a kilometer away!

Bohr

(1885-1962)

•Electrons can only exist at certain distances from the nucleus (called orbits, shells, or energy levels)

•The maximum number of electrons for the 1st energy level is two. Eight electrons is the maximum number for the 2nd and 3rd energy levels.

Electron Cloud Model• Aka Quantum Mechanical model

• Electrons have energy levels but no way to tell where they are at any given time

• Probable location – around nucleus in “Electron Cloud”

Working Model of Atom

• Protons and Neutrons cluster together to form the central core of atom

• AKA NUCLEUS

• Electrons occupy the space that surrounds the nucleus

Working Model of Atom

A fuzzy, cloudlike region surrounds the nucleus. Electrons exist in this region at certain allowed energy levels. As you can see, the atom is mostly empty space!

Working Model Definition An atom consists of a tiny, dense nucleus that is

surrounded by electrons.

The nucleus contains protons and neutrons. (An exception is the hydrogen-1 nucleus, which contains one proton only.) Protons and neutrons are also called nucleons.

The nucleus accounts for most of the mass of the atom.

Electrons exist at certain allowed energy levels. They occupy the volume of empty space that accounts for most of the volume of the atom.

Working Model of Atom

• Protons carry a positive charge.

• Electrons carry a negative charge.

• Neutrons carry no charge.

• A neutral atom always has equal numbers of electrons and protons.

Working Model of Atom

Subatomic particle

Relative charge

Symbol

Mass (g) Relative mass

Radius (in m)

proton 1+ p+ 1.67 10–24 1 10–15

neutron 0 n0 1.67 10–24 1 10–15

electron 1– e– 9.02 10–28 1/1850 smaller than 10–18

Not what we are working with…

Historical Models of the Atom Assignment

• Using your textbook and notes package fill in the table on page 17 of your notes package