Why do we study these things?

Basic research is carried out for the sake of increasing knowledge, suchas how and why a specific reaction occurs and what the properties of asubstance are.

Where might this type of work be done?

Applied research is generally carriedout to solve a problem.

Examples?

Technological development typicallyinvolves the production and use ofproducts that improve our quality oflife.

Examples?

Do these categories ever overlap?

Just imagine the possibilities.

So…….

• How do we go about solving problems?

“Scientific method”

• a series of steps followed to solve problems, including collecting data, formulating a hypothesis, testing the hypothesis, and stating conclusions

Observing is the use of the senses to obtain information.See Hear Taste SmellFeel

observe/collect data

Observation often involves making measurements and collecting data .The data may be descriptive (qualitative) or numerical (quantitative) in nature.

A system is a specific portion of matter in a given region of space that has been selected for study during anexperiment or observation.

Scientists use generalizations about the data to formulate a hypothesis, or testable statement.

A Hypothesis is an explanation that is based on prior scientific research or observations and that can be tested

It is not simply a guess. It is based on knowledge.

The hypothesis serves as a basis for making predictions and for carrying out further experiments.

Hypotheses are often drafted as “if-then” statements. The “then” part ofthe hypothesis is a prediction that is the basis for testing by experiment.

Testing a hypothesis requires experimentation that provides data to support or refute a hypothesis or theory.

Conducting an ExperimentDuring testing, the experimental conditions that remain constant are called controls, and any condition that changes is called a variable.

Any change observed is usually due to the effects of the variable.

Independent variable- what is manipulatedDependant variables change as a result.

“dependent variables are dependent on independent variables”

If testing reveals that the predictions were not correct, the hypothesis on which the predictions were based must be discarded or modified.

theorize

Scientists then try to explain the observed phenomena by constructing

a model which may lead to a new scientific theory

TheorizingA model in science is more than a physical object; it is an explanation of how phenomena occur and events are related.

They can be visual, verbal, or mathematical.

Theorize A theory is a broad generalization that explains a body of facts or phenomena. Theories are considered successful if they can predict the results of many new experiments.

So what do we study?

Matter anything that has mass and takes up space

So what is mass?

Mass is a measure of the amount of matter

Can we measure mass?

Volume is the amount of three dimensional space an object occupies

Can we measure volume?

L x W x H

Displacement method (for irregularly shaped objects)

What is this called and how do you read it?

What is matter made of?

2 types of particles make up all elements, compounds & mixtures

The fundamental building blocks of matter are atoms and molecules

An atom is the smallest unit of an element that maintains the chemical identity of that element.

An element is a pure substance thatcannot be broken down into simpler, stable substances and is made ofone type of atom

A molecule is the smallest unit of a compound that retains all of the properties of that compound.

A compound is a substance that can be broken down into simple stable substances. Each compound is made from the atoms of two or more elements that are chemically bonded.

There are some elements that exist in nature as molecules rather than single atoms

That’s a lot of talk about properties. How do we classify properties?

Extensive vs Intensiveproperties

Physical vs Chemicalproperties

Extensive properties depend on the amount of matter that is present. Can you list examples?

Extensive properties depend on the amount of matter that is present. Can you list examples?Mass Volume Length ResistanceTotal charge

Intensive properties do not depend on the amount of matter present.

Can you list examples?

Intensive properties do not depend on the amount of matter present.

Can you list examples?Density Conductivity Color

Luster Hardness Boiling PtMelting Pt

Paul McCord Univ of Texas/Austin

Physical change/ physical property

A physical property is a characteristic that can be observed or measuredwithout changing the identity of the substance

Examples?

A change in a substance that does not involve a change in the identity of the substance is called a physical change.

Examples?

A chemical property is a substance’s ability to undergo changes that transform it into different substances. Examples?

A change in which one or more substances are converted into different substances is called a chemical change or chemical reaction.Examples?

Physical changeone of the most common is phase change

kinetic theory of matter

all matter is composed of particles which have a certain amount of energy which allows them to move at different speeds depending on the

temperature (energy).

There are spaces between the particles and also attractive forces between particles when they

come close together.

kinetic theory of matterenergy

vsattractive forces

Increasing kinetic energy

Energy required (temp) is different for every material because attractive forces are

different for every material

Increasing kinetic energy

a change of state is a physical change of a substance from one state of matter to another. AKA “phase change”

Matter in the solid state has definite volume and definite shape. The particles are held close together by the strong attractive forces between them, and only vibrate about fixed points.

Matter in the liquid state has a definite volume but an indefinite shape; a liquid assumes the shape of its container. Liquids have this characteristic because the particles in them are close together but can move past one another. The particles in a liquid move more rapidly than those in a solid. This causes them to overcome temporarily the strong attractive forces between them, allowing the liquid to flow.

Notice the particles can move past one another more freely.

Matter in the gas state has neither definite volume nor definite shape. All gases have this characteristic because they are composed of particles that move very rapidly and are at great distances from one another compared with the particles of liquids and solids

The gas particles flow throughout the container.

Pretty much no attraction between particles

liquids and gases are fluids- they can flow

Plasma is a high-temperature physical state of matter in which atoms losemost of their electrons (one of the particles that make up atoms)

A plasma TV has chambers filled with ionized gas which has been electrically charged, in essence it is made of many fluorescent light bulbs

Chemical change/Chemical property

From earlier:A chemical property relates to a substance’s ability to undergo changes that transform it into different substances.

A change in which one or more substances are converted into different substances is called a chemical change or chemical reaction.

Chem Rxn basicsThe substances that react in a chemical

change are called the reactants.

The substances that are formed by the chemical change are called the

products

H + O2 H2OHydrogen reacts w/Oxygen to produce water

the reactants are Hydrogen and Oxygen, the product is water.

the arrow means “yields” or “forms”Its kind of like an = is algebra

How can you tell if a Chem Rxn has taken place?

The properties of the products will not be the same as those of the

reactants.

For example:

Sodium (Na) is a highly reactive metal. It has to be stored under special conditions to

keep it from posing a hazard.

It must be kept under mineral oil in order to prevent it from getting wet

And Chlorine (Cl) is a deadly gas in its elemental state.

Mustard Gas used in WWI

But together they make:

Table salt

Energy and ChangeThe law of conservation of energy

states that energy cannot be created nor can it be destroyed.

Whether a change is chemical or physical it involves energy. The energy associated with these changes may be

absorbed or released to the environment.

What does this mean?

Classification of matter

Any sample of matter can be placed into one of two groups:

Mixturesor

Pure substances

Mixture- a combination of two or more substances that are not chemically combined (meaning the components can be separated without a chemical reaction)

The components in a mixture may or may not be evenly distributed throughout the sample.

Homogeneous-describes something that has a uniform structure or

composition throughout

examples:

Salt water

Solution- a homogeneous mixture of two or more substances uniformly

dispersed throughout a single phase (can be solid, liquid or gas)

examples:

What is this guy breathing?

Heterogeneous- composed of dissimilar components.

Examples:

Pure substance- a sample of matter, either a single element or a single compound, that has definite chemical and physical properties. Any sample of a pure substance is

homogeneous.Examples:

A pure substance differs from a homogeneous mixture in the following ways:

1. Every sample of a given pure substance has exactly the same characteristicproperties. All samples of a pure substance have the same characteristic physical and chemical properties. These properties areso specific that they can be used to identify the substance. In contrast,the properties of a mixture depend on the relative amounts of themixture’s components.

2. Every sample of a given pure substance has exactly the same composition.Unlike mixtures, all samples of a pure substance have thesame makeup. For example, pure water is always 11.2% hydrogenand 88.8% oxygen by mass.

Pure substances are either compounds or elements. A compound can be decomposed, or broken down, into two or more simpler compounds or elements by a chemical change.

Generally we think of a molecule as the smallest representative component of the compound, and an atom as the smallest representative of the element. Representative meaning it retains the characteristic properties.

matter

Can it be separated by physical means?

mixtures Pure substance

Is the composition uniform ?

Can it be decomposed by chemical means?

Homogeneous mixture

Heterogeneous mixture

compound element

yes

yes yes

no

nono

Classification of matter flowchart

Classify the following materials as one of these:

• Mixture• Compound • Element

Plastic

Plastic

• Compound………………… why?

Aluminum

Aluminum

• Element…… why?

Gasoline

Gasoline

• Compound………….why?

Soil

Soil

• Mixture…why?

Introduction to the periodic tableThe elements are organized into groups based on similar chemical properties. This organization of elements is the periodic table

Each small square of the periodic table shows the symbol for the element and the atomic number. The symbol is comprised of one, two or three letters. The first letter is always capitalized.

Periodic table of the elements

Notice the lanthanide series and actinide series

Periodic table

• You need to know the name and symbol for elements #1-56, 72-86

The vertical columns of the periodic table are called groups, or families. They are numbered from 1 to 18 from left to right. Each group contains elements with similar chemical properties.

The horizontal rows of elements in the periodic table are called periods. Physical and chemical properties change somewhat regularly across a period. Elements that are close to each other in the same period tend to be more similar than elements that are farther apart.

-The two major categories of elements are metals (shown in red here) and nonmetals (shown in green here).

-Metalloids (shown in orange here) have properties that fall between those of metals and nonmetals.

a metal is an element that is a good electrical conductor and a good heat conductor.

Other properties many metals share:Solid at room temperature Malleable Ductile/high tensile strengthShiny

Zinc

copper

A nonmetal is an element that is a poor conductor of heat and electricity

Many nonmetals are gases at room temperature, a few are solids. Only one is liquid (Bromine) Low conductivity can be used to define nonmetals. There are fewer nonmetals than metals

chlorine

A metalloid (semi-metal) is an element that has some characteristics of metals and some characteristics of nonmetals. All metalloids are solids at room temperature. They tend to be less malleable than metals but not as brittle as nonmetals. Metalloids tend to be semiconductors of electricity

silicon

measurement

• Measurements represent quantities.• A quantity is something that has

magnitude, size, or amount

Scientists have agreed on a single measurement system called Le Système International d’Unités which is abbreviated SI.

This is what we refer to as Metric. This system was adopted in 1960 by the General Conference on Weights and Measures.

SI now has seven base units, and most other units are derived from these seven. Here they are with their base units1.Length -Meter2.Mass -Kilogram3.Time -Second4.Temperature -Kelvin5.Amount -Mole6.Electric current -Ampere7.Luminous intensity -Candela

LengthThe standard unit is the meter.

The defined standard for a meter is the length of the path traveled by lightin a vacuum during a time interval of1/299 792 458 of a second

temperatureMany people think the Celsius scale is the official temperature scale for SI

The Kelvin temperature scale is a scale that starts at a temperature corresponding to −273.15°C. That temperature is the lowest one possible. The temperature −273.15°C is referred to as absolute zero and is given a value of zero in the Kelvin scale

So how do you convert one to the other?

• Celsius to Kelvin +273• Kelvin to Celsius -273

Mass is a measure of the quantity ofmatter.

The SI standard unit for mass is the kilogram.

The defined standard of a kilogram is the unit of mass equal to the mass of theinternational prototype of the kilogram

Many SI units are combinations of the quantities just mentioned

Combinations of SI base units form derived units.

Derived units are produced by multiplying or dividing standardunits.

Examples of derived units

Area length × width m2

Volume length × width × height m3

Density mass/volume kg/m3

Density problems- smart board

Volume is the amount of space occupied by an object.

One cubic meter is equal to the volume of a cube whose edges are 1 m long

When measuring the volumes of liquids and gases, we often use a (non SI) unit called the liter. (Super important)

There are 1000 mL in 1 L.

Because there are also 1000 cm3 in a liter, the two units—milliliter and cubic centimeter—are interchangeable. “cc” is a term used for cubic centimeter

Density activity

• Find the density of a regularly shaped object

Conversion factor- a ratio that is derived from the equality of two different units and that can be used to convert from one unit to the other

You can use conversion factors to solve problems through dimensional analysis.Dimensional analysis is a mathematical technique that allows you to useunits to solve problems involving measurements

aka: factor label

Lets say you wanted to know how many minutes are in a day…………….

What do we know?

Lets say you wanted to know how many minutes are in a day…………….

What do we know?

There are 60 minutes in an hour.

Lets say you wanted to know how many minutes are in a day…………….

What do we know?

There are 60 minutes in an hour.

So: 60 min 1 hr 1 hr 60 min

Both of these are equalities, meaning they are equal to 1

Lets say you wanted to know how many minutes are in a day…………….

And we know………

24 hrs and 1 day are both equal to 1 1 day 24 hrs

So we use those to solve our problem through this method:

quantity given × conversion factor=quantity sought

Example:

1day x 24hrs x 60min = 1440 minutes 1day 1 hr

Accuracy vs Precision

• In measuring, scientists want to be both accurate and precise

• Accuracy-How close a measurement is to the actual value

• Precision- the degree to which repeated measurements under unchanged conditions show the same result (aka reproducibility)

Precision

I want my surgeon to be precise

Precisionbetter known in

athletics as consistency

Why be precise?

So…….

• Your lab group measures volume of a soda can. All three lab partners measure and get these results:

300mL 305mL 306mL

Is your group precise?

Is your group accurate?

Percentage error

calculated by subtracting the accepted value from the experimental value, dividing the difference by the accepted value, and then multiplying by 100.

Percentage Error

Theoretical value is the accepted value (known or given value)

Percentage error

• Percentage error has a negative value if the accepted value is greater than the experimental value. It has a positive value if the accepted value is less than the experimental value

significant figures

In measurement- all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated.

Cheat sheet…..

• Nonzero digits=always significant• Zero sandwiched=always significant• Zero to left= never significant• Zero to right= decimals makes it legit

Rules for determining the number of significant figures

1. All nonzero numbers reported are significant

In the nail measurement- 6.35cm there are 3 significant figures

What about zeroes?

• The following will help you determine which zeroes are significant digits

2. Zeros appearing between nonzero digits are significant.

a) 40.7 L has three significant figures. b) 87 009 km has five significant

figures.

3. Zeros appearing in front of all nonzero digits are not significant.

a) 0.095 897 m has five significant figures

b) 0.0009 kg has one significant figure.

• 4. Zeros at the end of a number and to the right of a decimal point are significant.

A) 85.00 g has four significant figures.B) 9.000 000 000 mm has 10 significant

figures.

5. Zeros at the end of a number but to the left of a decimal point may or may not be significant. If a zero has not been measured or estimated but is just a placeholder, it is not significant. A decimal point placed after zeros indicates that they are significant.

a) 2000 m may contain from one to four significant figures, depending on how many zeros are placeholders we can assume that 2000 m has one significant figure.

b) 2000. m contains four significant figures, indicated by the presence of the decimal point

summary

• Nonzero=significant• Zero sandwiched=significant• Zero to left= never• Zero to right= decimals makes it legit

5 rules for rounding Lets round to 3 significant digits. Look at the number after the “last” number, if:•greater than 5 -be increased by 1

42.68 g → 42.7 g⎯

•less than 5 -stay the same

17.32 m → 17.3 m⎯

• 5, followed by nonzero digits- be increased by 1 2.7851 cm → 2.79 cm⎯

• 5, not followed by nonzero digits, and preceded by an odd digit be increased by 1 4.635 kg → 4.64 kg (because 3 is odd)⎯

• 5, not followed by nonzero digits, and the preceding significant digit is even -stay the same 78.65 mL → 78.6 mL (because 6 is even)⎯

Math ops-sig digits

• Your answer can not be more precise than your least precise measurement

adding and subtracting

• When adding or subtracting decimals, the answer must have the same number of digits to the right of the decimal point as there are in the measurement having the fewest digits to the right of the decimal point.

25.1g+2.03g= 27.13g

but the answer must be rounded to only have one digit to the right of the

decimal (because of 25.1g)

round to 27.1g

multiplication and division

• In multiplication and division the answer can have no more significant figures than are in the measurement with the fewest number of significant figures

A density problem like this one3.05g / 8.47mL=0.360094451 g/mL

Would have an answer expressed in only three significant digits

.360 g/mL.

Mathematical OperationsUsing Scientific Notation

• Use the following rules for calculations involving scientific notation

+ and - operations can be performed only if the values have the same exponent

addition and subtraction-

4.2 × 104 kg +7.9 × 103 kg

Must be changed to:

4.2 × 104 kg+0.79 × 104 kg4.99 × 104 kg

(rounded to 5.0 × 104 kg)

or4.2 × 104 kg +7.9 × 103 kg

Must be changed to:

7.9 × 103 kg+42 × 103 kg49.9 × 103 kg

(4.99 × 104 kg rounded to 5.0 × 104 kg)

Multiplication- The first factors are multiplied, and

the exponents are added algebraically

(5.23 × 106 μm)(7.1 × 10−2 μm) =

First factors Exponents

(5.23 × 7.1)(106 + 10−2)= 37.133 × 104 μm2

(adjust to two significant digits)= 3.7 × 105 μm2

Division- The first factors are divided, and the

exponent of the denominator is subtracted from that of the numerator

5.44 × 107 g = 5.44 ×107−4

g/mol

8.1 × 104 mol 8.1

0.6716049383 × 103

(adjust to two significant figures) 6.7 × 102 g/mol

Problem solving

• Have some kind of an approach…….

Problem solving tips

• Analyze The first step in solving a quantitative word problem is to read the problem carefully at least twice and to analyze the information in it

Problem solving tips

• Plan The second step is to develop a plan for solving the problem. The plan should show how the information given is to be used to find the unknown

Problem solving tips

• Compute The third step involves substituting the data and necessary conversion factors into the plan you have developed. At this stage you calculate the answer, cancel units, and round the result to the correct number of significant figures.

• Evaluate Examine your answer to determine whether it is reasonable.

1. Check to see that the units are correct. If not, look at the conversion factors

2. Make an estimate of the expected answer. Use simpler, roundednumbers to do so. Compare

3. Check the order of magnitude in your answer. Does it seem reasonable compared with the values given in the problem?

4. Be sure that the answer is expressed using the correct number of significant figures

direct proportions

Two quantities are directly proportional to each other if dividing one by the other gives a constant

value

direct proportion

• When two variables, say “x” and “y”, are directly proportional to each other, the relationship can be expressed as

Y X

which is read as “y is proportional to x.”

direct proportion

• Example: Mass is proportional to volume for something that cannot be compressed

D= M/V

Mass vs Volume

Inverse Proportions

Two quantities are inversely proportional to each other if their

product is constant

(think “see saw”)

inverse proportion

• When two variables, say “x” and “y”, are inversely proportional to each other, the relationship can be expressed as

Y x

which is read as “y is proportional 1 divided by x.”

1

inverse proportion

example: in a container of gas, as volume is decreased, the pressure will rise.