DESCRIBE PHYSICAL & CHEMICAL CHANGES IN

TERMS OF ENDOTHERMIC & EXOTHERMIC PROCESSES

COS 5.0

WHAT YOU’LL LEARN• Explain the relationship between, matter atoms & elements• Categorize materials as pure substances or mixtures• Identify elements & compounds• Perform calculations involving density• Compare & Contrast physical & chemical properties• Determine how the law of conservation of mass applies to chemical changes• Compare & Contrast physical & chemical changes• Describe how to detect whether a chemical change has taken place.• Describe the four common states of matter.• List the different changes of state & describe how particles behave in each

state• Describe differences between endothermic & exothermic reactions

MATTER

COMPOSITIONMATTER

anything that has mass and takes up space (volume)

ATOMSsmallest particle of an element that has same properties of element

MOLECULES smallest unit of a substance that keeps all of physical and chemical properties of that substance.Two or more atoms that are chemically bonded

CLASSIFICATION

PURE SUBSTANCEPURE SUBSTANCE

• sample of matter, either a single sample of matter, either a single element or a single compound, that has element or a single compound, that has definite chemical and physical definite chemical and physical propertiesproperties

ELEMENTSELEMENTS

• substance that cannot be separated or broken down substance that cannot be separated or broken down into simpler substances by chemical meansinto simpler substances by chemical means

• Can be found as solids, liquids, or gasesCan be found as solids, liquids, or gases• Found on periodic tableFound on periodic table• Made of identical atomsMade of identical atoms• Pure substancesPure substances• Represented by abbreviations/symbols consisting Represented by abbreviations/symbols consisting

of one or two lettersof one or two letters• Examples: H, N, S, O, P, Au, Hg, NaExamples: H, N, S, O, P, Au, Hg, Na

COMPOUNDS

• substance made of atoms of two or more different elements that are chemically combined

• they always combine in same proportions.• Can be broken down through chemical means• Pure substances• Every compound is different from the

elements it contains.

CHEMICAL FORMULAS

• combo of chemical symbols and numbers to represent a substance.

• Subscript• represents number of atoms • located lower right of chemical

symbol

• Examples: NO2, NH3, NaCl, C6H6O6

MIXTURES• two or more substances that are NOT chemically

combined.• Variable composition• Each components retains their characteristic

properties• May be separated into pure substances by physical

methods• classified by how thoroughly the substances mix.• Two types

HOMOGENEOUS

may be pure substances or solutionsPure substances may be compounds or elementssubstances are evenly distributed “well mixed” Look/have the same composition throughout Particles are small and not easily recognizedcan be separated by physical means (dissolution, centrifuge, gravimetric filtering, etc.). Examples: milk, yogurt

HETEROGENEOUS

made of more than one kind of substance.substances aren’t mixed uniformly “least mixed”different particles in mixtures are large enough to be seeneasily separated by physical means (ie. density, polarity, metallic properties).

Matter Flowchart

MATTER

Can it be separated by physical means?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be decomposed by chemical means?

noyesIs the composition uniform?

noyes

PROPERTIES OF MATTER

PHYSICAL PROPERTIESPHYSICAL PROPERTIES

• characteristic of matter that can be directly characteristic of matter that can be directly observed without changing identity of observed without changing identity of substancesubstance

• you can see, such as color, shape, hardness, you can see, such as color, shape, hardness, and textureand texture

• easily measuredeasily measured

MASS

• amount of matter in an object• SI Unit: G r a m s (g)

WEIGHT

measure of pull of gravity on an object

SI Unit: N e w t o n s (N) Formula: W = m g

VOLUME

amount of space taken up by an object .

SI Unit: L i t e r s (L).

DENSITY

• mass per unit of volume

• Formula: Density = mass/volume

D = MV

D

M

V

Density1. An object has a volume of 825 cm3 and a density

of 13.6 g/cm3. Find its mass.

GIVEN:

V = 825 cm3

D = 13.6 g/cm3

M = ?

WORK:

M = DV

M = (13.6 g/cm3)(825cm3)

M = 11,220 g

DM

V

Density

2. A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid?

GIVEN:

D = 0.87 g/mL

V = ?

M = 25 g

DM

V

WORK:

V = M D

V = 25 g

0.87 g/mL

V = 28.7 mL

Density

3. You have a sample with a mass of 620 g & a volume of 753 cm3. Find density.

GIVEN:

M = 620 g

V = 753 cm3

D = ?

DM

V

WORK:

D = M V

D = 620 g

753 cm3

D = 0.82 g/cm3

Let’s Try Some More Density Problems

Density

1. If the mass of a rock is 500 g and its volume is 25 cm3, what is its density?

GIVEN:

M = 500 g

V = 25 cm3

D = ?

DM

V

WORK:

D = M V

D = 500 g

25 cm3

D = 20 g/cm3

Density

2. If the density of a liquid is 1.2 g/ml and its volume is 10 ml, what is its mass?

GIVEN:

V = 10 ml

D = 1.2 g/ml

M = ?

WORK:

M = DV

M = (1.2 g/ml)(10 ml)

M = 12 g

DM

V

Density

3. If Bob’s mass is 80 kg and his density is 1.6 kg/l, what is his volume?

GIVEN:

D = 1.6 kg/l

V = ?

M = 80 kg

DM

V

WORK:

V = M D

V = 80 kg

1.6 kg/l

V = 50 mL

BOILING POINT

• temperature and pressure at which a liquid becomes a gas

• liquid is still the same substance

MELTING POINTMELTING POINT

• temperature and pressure at which a solid becomes a liquid

VISCOSITYVISCOSITY

• resistance (difficulty) of a liquid to flow easily

• How “thick” or “thin” a liquid is

• high viscosity: Honey, motor oil, corn syrup

• low viscosity: water, milk, soda

CONDUCTIVITY

• ability to conduct heat or an electric current• High conductivity: metals (copper,

aluminum…)• Low conductivity: wood, rubber, plastic

MALLEABILEMALLEABILE

Ability to be hammered into a thin Ability to be hammered into a thin sheet.sheet.

DUCTILEDUCTILE

• Ability to be drawn into a thin wireAbility to be drawn into a thin wire

CHEMICAL PROPERTIESCHEMICAL PROPERTIES

• describes how a substance can change describes how a substance can change or react to form new substances. or react to form new substances.

FLAMMABILITYFLAMMABILITY

• ability of a substance to react in presence of oxygen and burn when exposed to a flame

REACTIVITY

• how easily a chemical reacts with other substances.

CHANGES OF MATTER

LAW OF CONSERVATION OF MATTER

• matter cannot be created nor destroyed.• It is just converted from one form to

another

STATES OF MATTER

SOLIDS SOLIDS Have a definite Have a definite

shapeshape Have a definite Have a definite

volumevolume Least amount of Least amount of

movement of movement of particles.particles.

Particles arranged Particles arranged in a regular pattern in a regular pattern and tightly packed.and tightly packed.

LIQUIDS• Have an indefinite

shape• Have a definite

volume• will assume the

shape of its container.• Particles are close

together but move about freely.

GASES

• Have an indefinite shape

• Have an indefinite volume

• Can fill any container

PLASMA

most common form of matter. makes up over 99% of the visible

universe dangerous, very high energy

(found in stars)

ENDOTHERMIC/EXOTHERMIC REACTIONS

Endothermic = heat energy is absorbed, cools surroundings

Exothermic = heat energy is released, warms surroundings

PHYSICAL CHANGES substance changes state but does not change

its chemical composition. Type of matter remains the same example: water freezing into ice, cutting a

piece of wood into smaller pieces

DISSOLVING

• to disintegrate, break up, or disperse• When a substance dissolves, the

molecules of the substance do not change.

Ways of Dissolving:• solid in a liquid,• gas in a liquid• liquid in a liquid

MELTING

to become altered from a solid to a liquid state usually by heat

endothermic ice cubes melting

BOILING

Change of a substance from a liquid to a gas.endothermic

two types:– Boiling:

• rapid • gas bubbles are produced throughout

– Evaporation• slow • occurs at the surface• is a cooling process• ocean water evaporates to form clouds & rain droplets

CONDENSATIONCONDENSATION

• Change of a gas to a liquid.

• exothermic

• water vapor turns into dew

SUBLIMATION

• Changing directly from solid to gas or gas to solid skipping the liquid state.

• endothermic

• formation of frost/snow & dry ice

FREEZING

• Changing from a liquid to a solid.• Particles lose kinetic energy and slow

down.• exothermic• water turns to ice

CHEMICAL CHANGES

• change of a substance into a new and different substance

• aka chemical reaction

• cannot be reversed by physical changes.

• impossible to “unbake” a cake.

CHEMICAL REACTIONS

Reactants: are the substances that enter a chemical reaction

Products: are the substances formed by a chemical reaction

CHARACTERISTICS & EXAMPLES OF CHEMICAL CHANGES

• Reaction with acids -------Digestion, fizzing• Reaction with oxygen (combustion) -------

Explosions, Burning• Ability to act as oxidizing agent -------- Rusting• Reaction with other elements ----- production of

heat, sound, light• Decomposition into simpler substances ------

change of smell, Decomposing• Corrosion ---- water lines becoming thin• Change in color -----Baking food• Production of a gas ------ Fermentation