Turbo TAKS Week 4 Lesson 1: Matter Lesson 2: Density Lesson 3: Periodic Table Lesson 4: Chemical Formulas

All matter can be classified into one of three areas:1. Elements2. Compounds3. Mixtures

Elements: Elements are the basic chemical structures that cannot be broken down.

Examples:•I- Iodine•Na- Sodium•Co- Cobalt•C- Carbon

Compounds: are formed when two or more atoms chemically combine.

They cannot be separated by physical means.

Examples:•NaCl- Salt•CO2- Carbon dioxide

Mixtures: are formed when two or more substances are mixed together but they are not chemically combined.

Mixtures can easily be separated by physical means. (Distillation, using a magnet, dissolving one in water – then letting the water evaporate.)

Heterogeneous Mixture: Mixtures that are not the same throughout. Examples: Pizza, SaladIf you take multiple samples of it, they may look different from each other!

Homogeneous Mixture: A mixture that is the same throughout. Examples: Kool-Aid, Brass

Physical/Chemical Changes:Physical Changes in matter that do not affect the chemical composition of the material. They often alter the volume, shape, or texture of the material, but it is often possible to “undo” a physical change and return the material to its former condition.

Ex. Phase changes (melting, freezing,etc)

It is the SAME SUBSTANCE.

Chemical Changes in matter do ALTER the chemical composition of the material. You get a NEW SUBSTANCE.

Ex. Producing a gas, heat change, color change Wood burns into ash and smoke. Stomach acid digests your

food. Metals rust (oxidation).

Lesson 2: Density, Viscosity, Buoyancy

DENSITYDensity is the ratio of mass to volume

and can be calculated by dividing the mass by the volume.

Whether your sample is cut in half, quarters, or little bitsy pieces, the density REMAINS THE SAME throughout!

*Denser liquids will sink under less

dense ones.

Liquids mixed in a container will separate into a column of distinct layers.

D = mass/volume

Common units of density include:

g/mL, g/cm3

Density

• Density of a substance changes as it goes from solid to liquid to gas.

• The only factor that affects density is temperature.

BUOYANCY – the ability to floatIf you place an object in a liquid like

water, the water will push upward with a buoyant force equal to the weight of the water displaced by the object.

If the average weight of the object is less than the weight of the displaced water, the object will float. This buoyancy explains why ships that weigh thousands of tons are able to float on the ocean.

If a material floats in water (buoyant) than its density is less than

1g/mL- if it sinks, it’s greater than 1 g/mL.

VISCOSITY

• A measure of how much fluid resists flowing. • High density = High viscosity

• Depends on temperature– Viscosity decreases as temperature increases.

• Low viscosity = water

• High viscosity = syrup or oil

Lesson 3: Periodic Table

Atoms• An atom is the smallest particle of an element that has all

the properties of that element

• The three parts of an atom are: – Protons (positive)– Neutrons (neutral)– Electrons (negative)

• Protons/Neutrons are found in the nucleus while electrons are found in an electron cloud outside the nucleus.

• Valence electrons are in the outermost energy level and are responsible for bonding.

Atomic Structure

• Sodium-23 The 23 is the mass number

• Atomic number – number of protons

• Mass number – number of protons and neutrons in the nucleus

Groups and Periods• Groups or families (vertical column) of elements

are listed by increasing atomic number and they have similar chemical properties. – Ex. calcium and magnesium would have similar

properties.

• Horizontal rows are called periods. – Group 1: Alkali Metals are the most reactive metals– Group 17: Halogens are the most reactive nonmetals.

These two groups are most likely to form bonds together.

– Group 18: Noble Gases: are resistant to bonding and largely nonreactive. This is because they have 8 valence electrons making them stable atoms.

Metals and NonmetalsProperties of Metals• Metals are electron

LOSERS.

• Located on the left side of the stair step

• Bright, metallic luster

• Conduct heat and electricity

• Malleable and ductile

Properties of Nonmetals• Nonmetals are electron LOVERS

(Gain/ Take electrons in chemical reactions)

• Poor conductors of heat and electricity

• Usually brittle

• Lower melting points

• Many are gases at room temperature

Lesson 4: Chemical Formulas

• Two types of formulas:

Ionic – metal + nonmetal

Covalent (molecular) = nonmetal + nonmetal

How do you write a chemical formula?

Crisscross method1. Write the symbols and oxidation numbers for each

ion. Write the ion with the positive charge on the left:

Pb+4 O-2

2. Criss-Cross the charges by writing each charge as the subscript for the other. Ignore the signs.

Pb+4 O-2 Pb2O4

3. Simplify the ratio. Do not write the subscript 1: PbO2

Polyatomic Ions

• A special class of ions where atoms are covalently bonded together

Short list of polyatomic ions