Name Keÿ Per.

Notes: Measurement (text Ch. 1 &lO)

NOTE: This set of class notes is not complete. We will be filling in information in class. If you are absent, it is yourresponsibility to get missing information from a fellow classmate or the chemistry website : http:#othschem.weebly.com/

I. Classification of Matter

Matter: anything that has mass and takes up space

Examples of matter: Wÿ.JrCÿ'j ÿiWI 12-,0oK Non-examples of matter: .ÿr'ÿer'ÿ ÿ/

3 states of matter and their properties: r'adio

Structure ofparticles

Gas

leSS cOÿ{ÿaCÿ-0 oo

iOOSe.,sÿ,reÿo "OUÿ"

o0

Liquid

HO

140

Motion ofparticles

Shape

deFiniltOnoÿ iÿrS owq

indeFiniÿ

Sbc,ÿ o]: coÿiÿtÿ

indtÿini4t_

Compressibility

Solid

Volume

d ePÿniÿ.,

indcFini+ÿ

Viscosity is a term related to fluids (liquids and gases). Viscosity is defined as resistance to flow.

What are 2 examples of highly viscous liquids? ÿ Oÿ3tÿf , I &V'Ok.

Matter can be classified according to the following diagram:

j Matter-ÿ..ÿ..ÿPure Substancesdefinite composition(one chemical formula)

Mixtures2 or more pure substances physicallycombined, can be separated physically,indefinite composition

ElementsOne type of atom;on Periodic Table

Compounds2 or more elementschemically bonded

HomogeneousAlso known as solutions;look uniform (same) throughout

HeterogeneousNot uniform (can seedifferent particles)

Ex: Fe, Ch

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Ex: H20

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Ex: Gatorade, salt water, alloys Ex: Italian saladdressing, oil & water

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II. Properties of Matter

Physical Property: a characteristic that is observed without changing the chemical makeup of thesubstance. Physical properties can be extensive or intensive.

Extensive properties depend on the amount of matter present; think "extent."(examples- mass, volume)

Intensive properties are not influenced by the amount of matter present; they are constant.(eexxamples: color, melting point, density, specific heat).

Chemical Property: characteristic that is observed when the substance undergoes a chemicalchange (reaction); these properties show how a substance reacts with other substances.

Examples" I'e(xCtivit-ÿ/ vvi+h vÿCXÿ6r 0ÿ" o,ÿ. Iÿ'On Rÿ'OL¢-ÿS uOi'Hÿ

oxygen usZ!I

III. Density

Density is an intensive property and can be found by dividing a substance's mass by its volume:

Density = mass D = rnvolume v

mass: measure of the quantity of matter an object containsvolume: the amount of space an object takes up

***How could you rearrange the equation to solve for mass? For volume?***

Density can be thought of as a measure of how tightly packed a substance's molecules are. Asubstance with a high density probably has massive particles that are closely packed. A substancewith a low density is likely to have less massive particles that are more loosely packed.

What state of matter is the least dense? 0tÿ The most dense (usually)? 601/ÿ

What substance is an important exception to this (the solid form is less dense than the liquid)?

What evidence can you think of to support this statement? i£ÿ" F'tOÿ-{-5

The density of a particular substance does not chanqe with the amount of that substance!Example: a cube of wood has a mass of 80.0 g and a volume of 100. cm3.What is the density of the block? If you cut the block in half, what is the density of each half?Prove it with math.

i::>= : : - ), •

V i O0.Cÿ.ÿÿ

2

3Aÿ E = inÿi v'(t [

IV. Chanqes in Matter

chemical rxn)A. Physical change: a change that does not produce a new substance (no } vinnExamples of physical changes: ibh&ÿe ÿ'ÿo.,qÿe,S LS->L.)) diÿ-ÿo Sol¥ iN

0

Phase changes are changes in the state of matter of a substance. They are always physicalchanges because the substance's chemical identity remains the same.

Example: Water is still H20, whether it's ice, liquid, or steam.

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Phase changes can be represented on a heating curve. The heating curve below is specific for wateronly. Label the phase changes and the direction of the arrows as endo- or exothermic. Assumestandard pressure (1 atrrO.

Temperature

Tm= O°C "->/

Tb = 100°C "->/J"

.2

Je

/EN

• Exothermic- heat is "exiting" or being released• Endothermic- heat is "entering" or being absorbed

Name of phase States of matter involved? Dir. of Heat flow Exothermic orchange (heat absorbed or endothermic?

removed?Melting Solid --) liquid Absorbed Endothermic

Freezing L --'7 ÿ rÿ,l.e.cLs¢ÿ ÿx0

Boiling L -'> ÿ2 QbSO(ÿecÿ ÿlqd 0

Condensing (2 -ÿ L. rele'&.ÿ-ct e×O

Sublimation*

Deposition** G "ÿ'ÿ f',¢'l e0lÿe4 eXo

3

Sublimation: solid to gas phase change without passing through the liquid phase(Examples: dry ice, solid air fresheners, mothballs, "shrinking" ice cubes)

Deposition: gas to solid phase change without passing through the liquid phase(Example: frost on a windshield--water vapor in the air crystallizes on the cold glass)

B. Chemical change (reaction): a change that does produce a new substanceExamples of chemical changes: I(ÿV'e& chrJ.nr4i¢lq ¢_0101".ÿ iQ FO, I[ I 12.ÿ/ÿ;ÿrlÿ i

e,pÿie q'Urn,nÿ ÿJ 6ÿouunI 8urninÿ 10ÿ5

One rule of thumb that can be useful in distinguishing physical from chemical changes:Ask yourself, Can the change be reversed? If yes: probably physical. If no: probably chemical.

Example: Milk goes sour. Can the change be reversed? NO. You cannot get the milk to taste goodagain, so it is a CHEMICAL change. A new substance (lactic acid) has been produced. This acid isformed when bacteria break down the lactose in the milk.

Example: An ice cube melts. Can the change be reversed? YES. Just put the water back in thefreezer. No new substance is produced. Remember, phase changes (changes between states ofmatter--solid, liquid, gas) are PHYSICAL changes!

***This rule is not perfect; it is just meant as a guide. For ex: consider the change that takes placewhen paper is cut into pieces. Can you get the whole sheet of paper back again? NO_ What kind ofchange is it? O H'qSiC&I Consider each case carefully. Don't just apply the rule without thinking.

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Besides the general indicator of a chemical reaction (new substances are formed), other specificsigns of a chemical reaction are:

1. a gas is produced2. light is produced3. a solid (precipitate) is formed from 2 liquids4. temperature change [temp goes up (exothermic) or down (endothermic)]5. permanent color change

• Exothermic reactions are those in which heat flows FROM the system of interest TO thesurroundings. Example of an exothermic chemical reaction: burning a log in a fireplace

Diagram this example below to show which way the heat energy flows for an exothermic process:(system = burning log) Which way does the arrow go?

SYSTEM(fire)

SURROUNDINGS(atmosphere)

• Endothermic reactions are those in which heat flows FROM the surroundings TO the systemof interest. Example of an endothermic chemical reaction: using a cold pack/ice for an injury

Diagram this example below to show which way the heat energy flows for an endothermic process:(system = cold pack/ice) Which way does the arrow go?

V. Enerqv

Energy is the capacity to do work. Energy is used to "make things happen." It is best understood bydescriptions and not by definition.

Some cateqories of ener,qy are described below:Kinetic: energy of motion (moving car)Potential: energy of position (boulder on hill)Chemical: energy stored in chemical bonds

(like bonds in food or fuel)

Thermal: heat energyElectrical: flowing electrons (current)Radiant: light energyNuclear: stored in nucleus of atoms

The Law of Conservation of Energy states that the amount of energy in the universe is constant; inother words, energy can be converted from one form to another, but is not created nor destroyed inthe process.

Can you trace the energy conversions that occur starting with the sun's light and ending with a rabbithopping? (answers may vary)

What about the energy conversions that occur starting with the sun's light and ending with a cardriving down the road? (answers may vary)

5

Thermal energy (HEAT) can be transported via 3 possible pathways:

1. Convection: the transfer of heat energy in a .qas or liquid (not in solids) by movement of currents.The heat moves with the fluid.

Example: At the beach, hot air rises, cooler air from the ocean comes in to replace it, and then thecool breeze cools your body..

2. Conduction: the transfer of heat energy through matter from particle to particle. The materials areactually touching during the transfer! Conduction is most effective in solids, but can occur in fluids.

Example: A chemical reaction occurring inside a test tube causes the test tube to heat up.

3. Radiation: the transfer of heat energy by electromagnetic waves. Radiation is the only form ofheat transfer that can occur in empty space, without the aid of any solids, liquids or gases.Sunlight is a type of electromagnetic wave. It travels through space via radiation.

Example: A lamp spreads light through a room.

How is thermal energy transported in the following examples?1. A beaker on a hot plate becomes warmer.

2. The pilot light in your car illuminates a map.

3. Hot soup transfers heat to the air above it.

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Vl. Chemical Reactions and the Law of Conservation of Mass

The starting materials are called reactants. The ending materials are called products. They areseparated by an arrow pointing toward the products. Reactants .qo on the left of the arrow, productson the ri,qht. The reaction reads left to right, just like a sentence.

REACTANTS "9' PRODUCTS

Example: photosynthesis6 CO2 + 6 H20 --) C6H1206 + 6 02

The Law of Conservation of Mass states that during a chemical reaction, matter cannot becreated or destroyed. This means that the original atoms can move around and find new partners,but all of the original atoms that were in the reactants WILL BE present in the products as well.

How many atoms of C are on the reactants side of the reaction above? __

How many atoms of H are on the reactants side of the reaction above? 12, products side? __

How many atoms of O are on the reactants side of the reaction above? ÿ products side? __

***This balanced equation illustrates that the Law of Conservation of Mass is obeyed!

products side?

Another way to illustrate the Law of Conservation of Mass:

6 002 4- 6 a20 --') 06H1206 + 602

The mass of the 02 is

264 g + 108 g = 180 g +

372. : "ÿ

- ÿ8o

Ifl 3***The mass of the reactants must equal the mass of the products!!!**

777 g

X

Now work throuqh this problem:

Mg + 2 HCI-) MgCI2 + H2

How many atoms of Mg are on the reactants side of the reaction above?

How many atoms of H are on the reactants side of the reaction above?

How many atoms of CI are on the reactants side of the reaction above? __

Provided the following masses, solve for the mass of the Mg.

I products side? [

products side? ÿ.

. products side? ÿ-

The mass of the Mg is

Mg + 2 HCI --) MgCI2?? g 73 g 95 g

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4- H22gJ

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