introduction to chemistry chapter 1. what is chemistry ? chemistry is – the study of the...

Introduction to ChemistryIntroduction to Chemistry

Chapter 1

What is Chemistry ?What is Chemistry ?

Chemistry is– the study of the composition of matter– the study of all substances and the changes that

they can undergo

Chemistry is everywhere!!!!

Chemistry ApplicationsChemistry Applications

Daily UsesMedicineBiotechnologyAgricultureEnvironmentSpace ExplorationTextiles

What is the scientific method?What is the scientific method?

The scientific method is– A systematic approach to solve a problem– An organized process used by scientists to do

research– A method by which scientists can verify the

work of others

Scientific Method - 5 StepsScientific Method - 5 Steps

1) Observation

2) Question- Propose a problem

3) Hypothesis- Tentative answer to question

4) Experiment- set up variables,collect data

5) Conclusion- Analyze data results

Parts of an ExperimentParts of an Experiment

Experiment: a set of controlled observations that test a hypothesis

Consists of:– Independent variable - the variable you plan to

change– Dependent variable - the variable that changes

in response to a change in the independent variable

Parts of an Experiment cont’dParts of an Experiment cont’d

– Control - a standard for comparison– Data – information/ observation recorded

can be either:

1) Qualitative: uses descriptive words

Example- colors

2) Quantitative: uses numbers

Class PracticeClass PracticeIdentify each piece of data as

either qualitative or quantitative1. Smells like apples 6. red2. 100 lbs 7. 40

mph3. 105 degrees C 8. round4. Tall 9. cold5. Pink with purple dots

Scientific MethodScientific MethodTheory & LawTheory & Law

Theory– a broad and extensively tested explanation of

“WHY” experiments give results.– Supported by many experiments– Considered successful if it can be used to make

predictions that are trueLaw

– a concise statement that summarizes the results of many observations and experiments

Observation vs. InferenceObservation vs. Inference

Observation – is an experience perceived through one or more

of the senses– What you feel, smell, see, hear, or taste

Example of observation– The temperature of a flask goes up as a

reaction proceeds

Observation vs Inference Observation vs Inference cont’dcont’d

Inference is – an interpretation of an observation– goes one step beyond an observation. – What “story” you create about

what you see, feel, hear, smell or taste

– based upon a direct observation

Observation vs Inference Observation vs Inference cont’dcont’d

Example– Observation: feel flask getting

hot and see the temperature rising on the thermometer

– Inference: an exothermic reaction (heat given off) is taking place

Observation vs Inference Observation vs Inference ExamplesExamples

Observation– A purple solution over time separates – Results in a blue and red color

Inference– Blue and red make up purple

The End!! The End!!

Lab – Alka Seltzer

HW – Experimental Design Worksheet

MatterMatter

Properties and Changes

Chapter 2

Four Phases of MatterFour Phases of MatterSolidsSolids

1. Solids – have a definite shape and volume– have strong intermolecular forces between

particles Therefore, the particles are very close to each

other What are intermolecular forces?

– Attractive forces BETWEEN molecules

– usually the most dense phase – In most cases incompressible

Four Phases of MatterFour Phases of MatterLiquidsLiquids

2. Liquids– have a definite volume– takes the shape of the container they are in– “flow” and are incompressible

What does that mean?

– the intermolecular forces are intermediate Weaker than solids, but stronger than gases therefore the densities are average

Four Phases of MatterFour Phases of MatterGasesGases

3. Gases– have no definite shape or volume (dependent

upon the container they fill),– very weak intermolecular forces so they have

very low densities– they are compressible and gases “diffuse”

Four Phases of MatterFour Phases of MatterPlasmaPlasma

4. Plasma– Energy is very high due to extremely high

temperatures– atoms are stripped of their electrons– they are “ionized”

What does that mean?

– moves quickly and unevenly – Examples

the sun and lightning

Classification of MatterClassification of MatterMatter

– anything that has mass and occupies space

Pure substance– has a constant, invariable composition– It’s identified by a formula or symbol – Examples

water- H2O – always has 2 hydrogens and 1 oxygen

Helium - He

Classification of MatterClassification of Matter

Compound-– Composed of two or more elements that

cannot be decomposed by physical means– chemically combined– Examples

Sodium chloride- NaCl Carbon dioxide- CO2


Element– simple substance that cannot be decomposed

into simpler substances by any chemical change


Mixtures– Composed of 2 or more components that can

be separated by physical means– There are no chemical bonds between the

separate parts – The components or parts can vary in

composition– 2 types of mixtures

2 Types of Mixtures2 Types of Mixtures

Homogeneous mixture– Sometimes called solutions– are evenly mixed– Appears as one component even though

there are 2 or more parts. – Example

plain jello Air salt water

2 Types of Mixtures cont’d2 Types of Mixtures cont’d

Heterogeneous mixture– are unevenly mixed– Can see separate components– Examples

dirt concrete muddy water

Heterogeneous MixturesHeterogeneous MixturesColloid vs. SuspensionsColloid vs. Suspensions

1) Colloids- particles are very small

- do not settle out of solution

-Examples:

Fog

smoke

whipped cream

2) Suspensions- particles are large

- settle out of solution

- Example:

Muddy water

Take a Break – Identification Take a Break – Identification and Classification Activityand Classification Activity

Physical Separation of Physical Separation of Mixtures TechniquesMixtures Techniques

1. Filtration- to separate by size– use filter paper and funnel– used for heterogeneous mixtures– Ex: muddy water

What can be separated?


2. Evaporation- boiling off liquid– Used for homogeneous solutions– Example: Salt water

3. Decant- to pour off liquid– Used for heterogeneous mixture


4. Distillation- separate a mixture of liquids by boiling points– How is that possible?

5. Chromatography- to separate pigments from a homogeneous solution– pigments separate because of differences in

1) mass 2) adsorption rates


6. Crystallization– formation of pure solid particles of a substance

from a solution containing the dissolved substance– What does that mean?– Example

Dissolve sugar into water Place a string into solution What forms around the string?

Conservation LawsConservation Laws

Law of Conservation of Matter (Mass)– matter is neither created or destroyed– In reactions:

Amount of reactants used = amount of products made

Law of Conservation of Energy – Energy is neither created or destroyed BUT rather it is

transferred from one form to another

The End!! The End!!

HW: Classification of matter worksheet

Finish Activity Worksheet on Identification and Classification

Experimental Design Quiz TOMORROW!!!

Physical and Chemical Physical and Chemical PropertiesProperties

Physical PropertiesPhysical Properties

properties that don’t involve a change in the chemical identity of the substance

can measure these properties/characteristics without changing the identity

Examples– melting point - electrical conductivity– boiling point– density - solubility

Physical Properties cont’dPhysical Properties cont’d

1) Extensive properties

- dependent upon the amount

of substance present

- Examples:

Mass, length, volume

Intensive properties

- independent of the amount of substance present

- Examples

Density, boiling point

Chemical PropertiesChemical Properties

Chemical property– refers to the way a substance undergoes a

chemical reaction to form new products– When you measure this property (characteristic)

at least one new product is formed

Examples: the ability to rot, rust, burn, ferment, grow, decay, sprout, combust

Physical and Chemical Physical and Chemical ChangeChange

Physical ChangePhysical Change Physical change

– a process that will alter a substance’s appearance without changing its composition or identity

Any change that describes a 1) Phase change - melting, freezing, evaporating, condensing 2) Size change - tearing, breaking, expanding, dissolving 3) Shape change - Hammering, stretching

Chemical ChangeChemical Change

Chemical Change-– a process that occurs that will change the

identity and composition of the reactants

Examples: Burning, rusting, exploding

Difference between Properties Difference between Properties and Changesand Changes

(physical & chemical)(physical & chemical)

PropertiesMeasure a

CHARACTERISTIC or trait

ChangesMeasure a process

Observations that Determine a Observations that Determine a Chemical Change in LabChemical Change in Lab

1. Gas is released• bubbles in liquid, smoke, odor

2. Heat is absorbed or released

3. Precipitate (solid) is formed in a homogeneous solution

– Start as liquid, then you see “things” floating or settled on the bottom

Observations that Determine a Observations that Determine a Chemical Change in LabChemical Change in Lab

4. Definite color change occurs– Color is a _______ property– but the process of changing colors is a chemical

change

5. Change in mass

6. Flash of light is released

EnergyEnergy

Energy is the capacity to do work

The Law of Conservation of Energy – states that energy cannot be created or destroyed BUT

rather transferred from one form to another

Forms of energy– Electrical, Heat (Thermal), Kinetic, Potential,

Chemical, Nuclear (Atomic), Wind, Hydraulic, Mechanical, Solar

The End!!The End!!

HW: Properties Worksheet

Law of Definite ProportionsLaw of Definite Proportions

Compounds are made up of elements

A compound is ALWAYS composed of the SAME elements in the SAME proportion by mass

What makes up water? How many of these atoms are present? Is this ALWAYS true?

Law of Definite ProportionsLaw of Definite ProportionsThe percent by mass shows the ratio of the

mass of each element to the total mass of the compound

Percent by mass (%) =

If you take table sugar (sucrose) from sugar cane or bag of sugar, how should the compositions compare to each other?

100

x

compoundofmass

elementofmass

Law of Definite ProportionsLaw of Definite ProportionsSucrose Analysis from Bag of Sucrose Analysis from Bag of

Sugar Sugar

ElementAnalysis by Mass

(g)Percent by mass

(%)

Carbon 8.44 g C 42.20 % C

Hydrogen 1.30 g H 6.50 % H

Oxygen 10.26 g O 51.30 % O

Total 20 g Sucrose 100 %

Law of Definite ProportionsLaw of Definite ProportionsSucrose Analysis from Sugar Sucrose Analysis from Sugar

CaneCane

ElementAnalysis by Mass

(g)Percent by mass

(%)

Carbon 211.0 g C 42.20 % C

Hydrogen 32.5 g H 6.50 % H

Oxygen 256.5 g O 51.30 % O

Total 500 g Sucrose 100 %

The End is really here!!The End is really here!!January 15January 15

Study for test tomorrow!Review packets due!

Do you know the 1st 7 elements?Don’t forget your calculators!!

Sharing NOT allowed!!

Physical & Chemical Change Physical & Chemical Change LabLab

Part One:Part One:Touch and describe the copper before &

after heatingDon’t forget to record the masses BEFORE

& AFTER of the crucible and copper (Cu) together!!– Individual mass is NOT important!!

While waiting for the crucible to cool for 10 minutes, do NOT turn off the burner, go on to part 3 & 4

Part Three:Part Three:

dissolve salt with a glass stirring rod– be careful NOT to break the test tube– after using, make sure to rinse off!!

Part 4Part 4

Use only ONE wooden splint that is in your tray!!

Hold test tube at the top end!!Dirty but clean???

Part Two:Part Two:

– Get 3 toothpicks to mix the solutions; you can use both ends

– after you mix, wait at least 3 minutes to see if precipitates form (lift well plate)

Assignment SheetsAssignment Sheets The # in ( ) are total possible points for that grade Homework: Parent/ Student Contract (10)

Quiz: Binder Week #1 (10) Unit 1 Quiz (18)

Lab: Safety Test (50)

introduction to chemistry chapter 1. what is chemistry ? chemistry is – the study of the...

Documents