Chapter 3 Notes II CHEMICAL & PHYSICAL

Properties/Changes

PHYSICAL PROPERTIES

color odorDensity and

hardness Melting point

Boiling point

solubility

• A quality or condition of a substance that can be observed or measured without changing the substance’s composition

• What are some examples?

Extensive vs. Intensive Physical Properties

•Extensive - dependent on the amount of the substance

– size, mass, length, volume.

•Intensive - independent of the amount of the substance

– density, boiling pt, melting pt, hardness, magnetism

– Help with identification because they are specific to the substance.

STATES OF MATTER

• Matter’s state is a physical property

Definite shape, definite volume

solid

No definite shape, definite volume

liquid

No definite shape, no definite volume

gas

States of Matter

SOLIDMatter that has its own definite shape and volume.

Tightly packed solids are incompressible.

Due to definite shape, some solids may not take the

shape of their container.

Not defined by hardness-wax, cheese, etc are solids

although not hard.

States of Matter

LIQUIDMatter that flows, has constant volume, and takes up the

shape of its container.

Particles are not rigidly held in place.

Particles packed less closely than in solid.

Particles able to move past one another.

Regardless of the container, volume stays the same.

States of Matter

GASMatter that flows to conform to the shape of and fill its

container.

Can be compressed due to space in between particles.

Particles less close together than solid or liquid.

Vapor is NOT the same as a gas. A vapor is the gaseous state of a substance that is solid or liquid at room temp.

Change of Phases

Kinetic Molecular Theory

“All matter consists of extremely tiny

particles which are in constant motion.”

Chemical Properties

• Chemical property - A characteristic of a substance that changes when in contact with another substance– Examples?????

• Flammability • Ability to react • Rusting of nails• Burning of paper

PHYSICAL CHANGES

• Physical Change:– Change in the appearance only, not in its

chemical make-up. – Examples: (change in…)

• Color• Shape• Temperature • Size• Phase

Chemical Change

• Chemical changesChemical changes…changes result in a re-…changes result in a re-arrangement or recombination of atoms (arrangement or recombination of atoms (NEWNEW substance!).substance!).– can’t get original substance back w/out chemical can’t get original substance back w/out chemical

reaction.reaction.– Examples: Examples:

• Silver tarnishingSilver tarnishing• Apple rottingApple rotting

CHEMICAL REACTIONS

• The ability of a substance to react and form new substances is called a chemical property.

• In a chemical reaction, one or more substances change into new substances.

• A reaction starts with the reactants, and the substances formed are called products.

• How do you know if a chemical reaction is occuring?

4 CLUES TO CHEMICAL REACTION

4 CLUES TO CHEMICAL REACTION

1) A color change occurs.

4 CLUES TO CHEMICAL REACTION

2) A gas is formed.

4 CLUES TO CHEMICAL REACTION

3) Heat or light is either produced or absorbed.

4 CLUES TO CHEMICAL REACTION

4) A solid is formed from two liquids.

This solid is usually called a precipitate.

CHEMICAL OR PHYSICAL CHANGE?

• Baking cookies• Boiling water• Dissolving salt• Burning firewood• Milk spoiling• Metal rusting• Tearing paper• Melting ice

Law of Conservation of MassLaw of Conservation of Mass

‘ ‘matter cannot be created or destroyed’matter cannot be created or destroyed’ total mass on reactant side total mass on reactant side MUSTMUST = mass on product side. = mass on product side.

~ ‘what goes into the rxn. must come out!’~ ‘what goes into the rxn. must come out!’

Ex…Ex…

A + B C + DA + B C + D5 grams5 grams 8 grams8 grams 2 grams2 grams __________________

13 grams13 grams

11 grams11 grams

DensityDensity

DensityDensity…amount of matter present in a given volume.…amount of matter present in a given volume.

~ how heavy a substance is~ how heavy a substance is

D = m/vD = m/v

units = g/ml or g/cmunits = g/ml or g/cm33

Density problems…Density problems…

1. A nail has a vol. of 0.880 cm1. A nail has a vol. of 0.880 cm33 and a mass of 6.920 grams. and a mass of 6.920 grams.

What is the What is the densitydensity of the nail?of the nail?

D = m/vD = m/v D = 6.920 g / 0.880 cmD = 6.920 g / 0.880 cm33 D = 7.86 g/cmD = 7.86 g/cm33

2. Vegetable oil has a density of 0.916 g/ml. Calculate the2. Vegetable oil has a density of 0.916 g/ml. Calculate themassmass of 500.0 ml of oil. of 500.0 ml of oil.

m = D(v)m = D(v) m = 0.916 g/ml (500.0 ml)m = 0.916 g/ml (500.0 ml) m = 458 gramsm = 458 grams

3. The density of a piece of wood is 0.86 g/cm3. The density of a piece of wood is 0.86 g/cm33. What is the. What is thevolumevolume of the wood if its mass is 75 grams? of the wood if its mass is 75 grams?

v = m/Dv = m/D v = 75 g v = 75 g ÷÷ 0.86 g/cm 0.86 g/cm33 v = 87 cmv = 87 cm33

To calculate density of an irregular object…To calculate density of an irregular object…

~ find mass of object using balance~ find mass of object using balance

~ find volume of object by using the water displacement~ find volume of object by using the water displacementmethodmethod

** water displacement will not work if solid dissolves or floats in water.

Separation Techniques

• It is important to know how to separate mixtures into

their component parts.

• Remember mixtures are physically combined, not

chemically combined.

• Mixtures can be separated using techniques based on

their physical properties.

Filtration

• Heterogeneous mixtures composed of solids and liquids can be separated using filtration.

Filtration uses a porous barrier to separate solids from liquids.

Below filter paper is folded into a cone shape and placed in a funnel, then a mixture is poured through the filter paper. The liquids pour through to filter paper but the solid are trapped by the filter paper.

Distillation

Most mixtures of homogeneous liquids are separated by distillation.

• Distillation is based on different boiling points of the substances involved.

• Distillation is the process of heating a mixture until the substance with the lowest boiling point boils to a vapor, capturing and cooling the resultant hot vapors in a condenser, and collecting the condensed vapors in a receiving flask.

Crystallization

• Homogeneous mixtures can be separated into pure crystals and liquid using crystallization.

In order for crystallization to occur, there must be as much of the dissolved solid that the solution can hold. Heating and cooling the solution or adding a small amount of the substance causes the substance to come out of solution and crystals to form.

Crystallization is a technique that improves the purity of the solid.

Chromatography

• Components of a mixture can be separated based on the how quickly it moves up the filter paper or stationary phase .

In paper chromatography, a sample of the substance to be separated is placed on filter paper. Then it is solvent so that the solvent gradually moves up the paper and separated the mixture into it’s components.

Chromatography is used in analytical chemistry to investigate what unknown chemicals are composed of.