Bellwork

Which of the following represents a mixture?

- a piece of copper wire - oxygen in a pressurized tank - a slice of mushroom pizza - a lead fishing weight

Chapter 13 Review

• Matter: anything that has mass and takes up space • Mass – the amount of matter in something • Volume – the amount of space something occupies • Which of the following is matter?

– A car?

– A box?

– You?

What is a property?

A Property is a characteristic of a substance that can be observed.

Physical Property

A physical property is one that can be observed without changing the identity of the substance.

Examples

• Malleability: the ability to be hammered into a thin sheet • Ductility: the ability to be stretched into a wire • Melting/freezing point • Boiling point • Density • Solubility • Specific heat: the amount of heat required to heat a substance 1 degree Celsius • Luster: shiny, matt

Special Physical Properties

• Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure water = 0 pressure o C • Boiling point: the temperature at which a substance changes from a liquid to a gas at a given water = 100 o C

Density

• Density is the amount of mass per unit of volume.

• Like many other properties it can be used to identify a substance.

• The density of water is 1.0g/mL

Calculating Density

D = m/V = g/mL = g/cm 3

Ex: A cube has a mass of 2.8 g and occupies a volume of 3.67 ml. Would this object float or sink in water?

Mass = 2.8 g Volume = 3.67 mL D = 2.8g/3.67 mL= 0.76 g/mL

Identification by Density

A liquid has a mass of 25.6 g and a volume of 31.6 mL. Use the table below to identify the substance.

M=25.6 g V=31.6 mL D = 25.6 g/31.6 mL D= 0.81 g/mL The substance is ethanol.

Chemical Properties

A Chemical property is a property that can only be observed by changing the identity of the substance Examples: •flammability •ability to rust •reactivity with vinegar

Element

An element is a pure substance that cannot be broken down into any other substance by chemical or physical means.

Examples: •aluminum •zinc •oxygen

Atom

Elements are comprised of atoms, which are so small they cannot be seen even with a microscope.

Molecule

Atoms bond together chemically to form molecules.

Compound

A compound is a pure substance made of 2 or more elements chemically combined in a set ratio. Compounds cannot be easily separated.

Mixture

A mixture is a pure substance made of 2 or more elements, compounds, or both, that are together yet not chemically bonded and therefore can be separated by physical means. Heterogeneous Homogeneous

Changes

• Physical change – substance maintains its chemical makeup Ex: state changes, dissolving • Chemical change– substance becomes something else entirely Ex: burning, oxidation

Chemical Reactions

• • Endothermic reactions must absorb heat/energy in order for the reaction to take place. This intake of energy may be

observed as a decrease in

temperature as the reaction proceeds. Exothermic reactions release heat from the reaction.

Chemical Reactions

• Reactants – are the chemicals that go into a reaction.

• Products – are the chemicals products that are created by the reaction.

Law of Conservation of Matter

States that the: Mass of the reactants = Mass of the Products (in a closed system) Ex: 5 g of sodium(Na) + 5 g of chloride (Cl) yields 10g of table salt (NaCl)

Conservation of Matter Lab

Objective: To demonstrate the Law of Conservation of Matter by reacting vinegar & baking soda in a closed system.

Bellwork

What is the difference between a compound and a mixture?

Venn Diagram

ENERGY!

2 Main Types of Energy

Temperature = Energy

Temperature

Law of Conservation of Matter

States that the: Mass of the reactants = Mass of the Products Also stated as matter cannot be created nor destroyed… only transformed.

Law of Conservation of Energy

Energy also cannot be created nor destroyed… only transformed or transferred.

Law of Conservation of Energy

Exothermic

Produces Heat

Endothermic

Soaks up heat from the surroundings; observed as a decrease in temperature 25 ml citric acid soln 15 g baking soda

Bellwork

Which pure substance is composed of more than one element?

- carbon - gold - water - sodium

Intro.

The PERIODIC TABLE contains information about the different ELEMENTS that make up all the solids, liquids, and gases in the known universe.

Natural vs. Synthetic

The majority of the known elements are naturally occurring, however all elements above 92, are known as: SYNTHETIC elements having been created in a lab.

Atoms

Elements are one or more identical ATOMS and each element has its own unique atom that looks different than all the other elements.

Organization

Elements are organized on the periodic table by their ATOMIC NUMBER, which is the number of PROTONS in the nucleus.

Isotopes

Atoms of the same element can have different numbers of NEUTRONS; the different possible versions of which are called ISOTOPES.

Calculate # of Neutrons

To determine the average number of neutrons in an element: Round the atomic mass to the nearest whole number and subtract the atomic number (of protons). Ex: K 39 – 19 = 20 neutrons.

Atomic Mass

The ATOMIC MASS listed on the periodic table is an average of the mass of all known isotopes of that element.

Symbols

Hg – Mercury Au – Gold Pb – Lead Sn – Tin Ag – Silver Cu – Copper Fe – Iron K – Potassium Na - Sodium

Patterns in the Table

The PROPERTIES of an element can be predicted by their location on the periodic table.

Group 1

Alkali Metals – do not occur uncombined in nature; highly chemically reactive

Group 2

Alkaline Earth Metals – also do not occur uncombined; good conductors

Groups 3-12

Transition Metals – also good conductors; form colorful compounds that last a long time since they are not highly chemically reactive

Lanthanides

Soft, shiny, malleable metals with high conductivity

Actinides

Most are synthetic and the nuclei are unstable (meaning they break apart quickly)

Metalloids

Along the stair step line – (7) METALLOIDS that have properties of metals and non metals are very useful for their varying abilities to conduct electricity (i.e. silicon semi-conductors in computer chips).

Non-Metals

The NON-METALS are not good conductors but they combine with others readily to form compounds.

Many of these elements are crucial in creating and maintaining life (C, N, O, P, S).

Group 17

HALOGENS - meaning “salt forming” They are DIATOMIC, meaning they never exist as a single atom.

Group 18

NOBLE GASES – do not bond with other elements at all, hence why they are called “noble”

Bellwork

The element silicon is best used for which purpose?

- as a container to keep coffee hot - as a semiconductor in a computer chip - as a material to make airplane frames - as a malleable material for coins and jewelry

Protons & Electrons

Atoms are in general NEUTRAL since they generally have the same number of protons as electrons in their pure form. They strive at all times to maintain their neutrality.

Electrons

We know already that ELECTRONS are orbiting around the nucleus of the atom. Where they are orbiting helps us to make some predictions about how and if an element will combine with other elements (reactivity).

Energy Levels

There are several ENERGY LEVELS within the electron cloud and each can only hold a certain number of electrons.

The period/row on which an element can be found will tell you how many energy levels there are in an atom of that element.

Filling the Energy Levels

1st energy level holds 2 electrons 2nd energy level holds 8 electrons 3rd energy level holds 18 electrons There are 7 energy levels in total but we will only concern ourselves now with the first 18 elements so we will only need to know about the first 3.

Valence Electrons

Not all energy levels will be filled and the electrons that reside in the outermost energy level are called the VALENCE ELECTRONS.

You can find out at a glance how many valence electrons an element has by looking at the group number.

Bell Work

How can a scientist, using the periodic table, find an element with properties similar to another element?

- by comparing density - by finding it’s periodic group - by comparing malleability - by comparing atomic weight

Bell Work

Which periodic group does the element chlorine belong to?

- alkali metals - alkali earth metals - noble gases - halogens

Bell Work

How would you calculate the number of neutrons in an atom of a given element?

Bell Work

What is the NAME of the family/group that fluorine belongs to?

Bell Work

What is the NAME of the family/group that Potassium belongs to?

*** Don’t forget to have your completed Periodic Table from yesterday out when I come around with the stamp 

Bell Work

Which of the following correctly compares the elements on the right side of the periodic table with the elements on the left?

- The elements on the right side are generally denser than the elements on the left side.

- The elements on the left side are better conductors of electricity than the elements on the right side.

- The elements on the right side are better conductors of thermal energy than those on the left side.

- The elements on the left side have lower melting point than the elements on the right side.

*** Don’t forget to have your completed homework out 

Bellwork

Which element is LEAST likely to combine with another element to form a molecule?

- Chlorine (Cl), a halogen - Iron (Fe), a metal - Neon (Ne), a noble gas - Silicon (Si), a metalloid

Molecules

2 or more atoms help together by chemical bonds

Valence Electrons

Are the electrons on the outermost shell of an atom that participate in bonding.

Lewis Dot Structures

Diagrams that show electrons, bonding, and lone pairs of electrons.

Covalent Bonds

A chemical bond that involves the SHARING of their valence electrons.

Ionic Bonds

A bond that involves the TRANSFER of valence electrons from one atom to another.

Ions

Atoms that gain or lose electrons, therefore having a charge.

Cations +

Atoms with a positive charge. These are metals since they lose electrons because they have one or 2 to spare.

Anions -

Atoms with a negative charge. These are nonmetals since they gain electrons because they only need 1 or 2 to become stable.

Ionizing Energy

The amount of energy required to remove an electron from an atom.

Bellwork

What do these chemicals have in common?

Cu SO 4 ZnCl 4 Fe 2 O 3 - Number of atoms - Presence of oxygen - Presence of metal - Number of bonds

Bellwork

You have a sample of an unknown element. At room temperature, this element is a gas & reacts easily with other elements to form compounds. In which column of the periodic table does this element most likely belong?

- IIA - VA - VIIA - VIIIA

Chemical Reactions

Chemical change occurs when bonds break and new bonds are formed.

The chemical composition (makeup) of the substance(s) has been altered.

Evidence of Chemical Change

• Change of properties • heat absorbed -endothermic • heat released – exothermic • gas formation (O 2 , CO 2 ) • Precipitate formation*

Chemical Equations

Reactants 

2 H 2 + O 2

 Products

2 H 2 0

Coefficient – # of molecules Subscript - # of atoms

Types of Chemical Reactions

• Synthesis A + B C   AB + CD C • Decomposition A + B • Replacement  AD BC

Conservation of Mass

Mass of Reactants = Mass of Products

Remember the lab where we reacted baking soda and vinegar and trapped the CO2 in the balloon!

BellWork

Five molecules

methane?

- CH 4 of methane contain five carbon atoms and 20 hydrogen atoms. What is the chemical formula of - C 2 H 8 - C 4 H 2 0 - C 5 H 2 0

Activation Energy

Activation Energy is the minimum amount of energy required to start a chemical reaction.

It has a cascading effect.

An endothermic reaction requires A LOT of activation energy.

Surface Area

If you break the reactants into smaller pieces then there is more surface area in contact with the other reactant. Thereby increasing the chance that 2 oppositely charged atoms can bond together.

Temperature

If you increase the temperature then the molecules are moving faster and thereby making connections more frequently.

Concentration

Concentration is the amount of a substance in a given volume. Increasing the concentration of a substance means there are more atoms or molecules available for bonding.

Catalysts

Catalysts increase the rate of reaction by lowering the activation energy required to start the reaction.

They are not reactants and they are not consumed during a reaction.

Inhibitors

Inhibitors slow reactions by interfering with the reactants ability to get to each other.

Demo Time

Decomposition of Hydrogen Peroxide

KI

2H

2

O

2 

2H

2

O + O

2

Follow Up Questions

Answer on a sheet of notebook paper: 1. Describe what happened in this demonstration.

2. Is this an endothermic or exothermic reaction?

3. What is a catalyst? 4. Name the catalyst in this demonstration. 5. Could it be included as a reactant in the chemical equation?

Acids

Produce H + Ex: HCl  ions in H 2 O H + + Cl Properties: •Tastes sour • Corrosive reaction w/metal • Reacts w/CO 3 2 to make CO 2 • Turns blue litmus paper red

Examples of Acids

• HCl – hydrochloric acid • CH 3 CO 2 H – acetic acid (vinegar) • H 2 SO 4 – sulfuric acid • Ascorbic Acid – Vitamin C (citrus) • Fertilizers – Nitric & Phosphoric Acid • Lactic Acid

Bases

Produce OH Ex: NH 3 ions in H 2 O + H 2 O  NH 4 + + OH •Tastes bitter • feels slippery • Turns red litmus paper blue

Examples of Bases

• NaHCO • household cleaners including: • NH 3 3 – baking soda - ammonia • Drain Cleaner

Strength

The strength of an acid or a base is based on how well it produces ions in water.

Strong Acids – HCl & H 2 SO 4 Strong Bases - NaOH

Measuring Strength

pH

= Potential Hydrogen Range of values from 0 to 14 that describes the concentration of H + ions in a substance.

Since we are measuring H the more acidic it is!

+ ions and they are produced by acids, we can expect the higher it is on the scale,

Safety

Know the pH (strength) of the acid or base you are handling.

Everything from 2-11 is in the safe zone.

Precautions

When working with a strong acid or base (0-2 or 11-14) be sure to wear goggles…even if it’s a dilute solution!

For spills Pour vinegar on a base & sodium bicarbonate on an acid…because…

Acid Base Neutralization

Displacement reaction Acid + Base  (liquid) water +(solid) salt Salt = Group 1-2 Metal + a halogen

Demo Time

NaHCO 3 + NaOH  Na 2 CO 3 + H 2 O

Precipitate Reactions

If the ions in 2 solutions combine to form a solid and that solid is NOT soluble with the solvent produced a precipitate will form.

 Example Fe(NO 3 ) 3 (aq) + 3 NaOH(aq)  Fe(OH) 3 (s) + 3 NaNO 3 (aq)

Demo Time

Cu(NO 3 ) 2 (aq) + 2 NaOH(aq)  Cu(OH) 2 (s) + 2 NaNO 3 (aq)