Matter and Change

• What is Chemistry?• Scientific Method• Properties of the States of Matter• Properties and Changes in Matter• Conservation of Mass and Energy• Classifications of Matter• Introduction to the Periodic Table

What is Chemistry?

Chemistry is the study of the composition, structure, and properties of matter and the changes it undergoes.

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What are the Six Branches of Chemistry?

1. Organic Chemistry

2. Inorganic Chemistry

3. Physical Chemistry

4. Analytical Chemistry

5. Biochemistry

6. Theoretical Chemistry

The six branches of chemistry often overlap.

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Organic Chemistry

Organic Chemistry is the study of most carbon containing compounds.

An organic chemist might:• create and analyze new chemicals made from carbon-

containing building blocks.

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Back to Branches of Chemistry

Inorganic ChemistryInorganic Chemistry is the study of all substances not classified as organic chemicals, which includes the chemistry of all substances containing elements other than carbon.

An inorganic chemist might:• study and develop new materials to improve existing

products or make new ones• determine ways to strengthen or combine materials or

develop new materials for use in a variety of products

This year you will be learning inorganic chemistry.

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Physical Chemistry

Physical Chemistry is the study of the properties and changes of matter and their relation to energy.

A physical chemist might:• develop new types of instruments to measure data.• measure the amount of energy released or absorbed in

chemical processes• study the mechanisms in which chemical reactions

occur

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Analytical Chemistry

Analytical Chemistry is the identification of the components and composition of materials.

An analytical chemist might:• make measurements and calculations to solve

laboratory and math-based research problems• analyze the composition of medicines and research

new combinations of compounds to use as drugs

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Biochemistry

Biochemistry is the study of the substances and processes occurring in living things

A biochemist might:• identify enzymes and determine reaction mechanisms

for biochemical reactions• develop new foods, flavors and preservatives, and

study how vitamins and minerals are used in the body.• develop new drugs and study their effects.

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Theoretical Chemistry

Theoretical Chemistry – the use of mathematics and computers to understand the principles behind observed chemical behavior and to design and predict the properties of new compounds.

A theoretical chemist might:• use a computer to explain the physical and chemical

properties of various compounds in terms of their molecular structures.

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Back to Branches of Chemistry

Identify the branch of chemistry which would be associated with each of the following tasks.

1. creating analyzing new chemicals made from carbon-containing building blocks.

2. analyzing the composition of medicines and researching new combinations of compounds to use as drugs.

3. identifying enzymes and determining reaction mechanisms for biochemical reactions.

4. utilization of a computer to explain the physical and chemical properties of various compounds in terms of their molecular structures.

5. measuring the amount of energy released or absorbed in chemical processes.

6. studying and developing new materials to improve existing products or make new ones.

organic chemistry

analytical chemistry

biochemistry

theoretical chemistry

physical chemistry

inorganic chemistry

Scientific Method

The scientific method is a way to ask and answer scientific questions by making observations and doing experiments.

Scientists use the scientific method to search for cause and effect relationships in nature.

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Observations

Observations are made through the use of your senses. Your five senses are:

Touch Hearing

Smell Taste

Sight

Observations must be specific and accurate, not relative, so that they mean the same to everyone.

Incorrect – The burning bag smelled nasty.

Correct – The burning bag smelled similar to rotten eggs.

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Quantitative vs. Qualitative Observations

Observations may be qualitative or quantitative.

Qualitative Observations – factual descriptions that do not use numbers.

Example: Mr. Smith has brown hair.

Quantitative Observations – factual descriptions that use numbers.

Example: Mr. Smith is six feet tall.

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Inferences

Inferences are possible explanations based upon observations and previous knowledge.

Example: You leave the movie theater and see that the ground is wet so you infer that it rained.

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Classify each of the following statements as observations or inferences.

1. The bird feeder is empty.

2. The birds must have eaten all the seeds in the feeder.

3. The car has a flat tire.

4. The driver must have run over a nail.

observation

inference

observation

inference

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Steps in the Scientific Method

Step 1: Ask a Question

The scientific method starts when you ask a question about something that you observe.

Ask a Question

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Steps in the Scientific Method

Step 2: Gather Information

Information can be gathered in many ways.

Some examples of ways in which information could be gathered include:

Making observations

Conducting background research

Ask a Question

Gather Information

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Steps in the Scientific Method

Step 3: Formulate a hypothesis.

A hypothesis is a tentative explanation (educated guess) for an event.

Hypothesis are sometimes written as “if-then” statements.

For example, If I eat 2 gallons of ice cream, then I will get sick.

Ask a Question

Gather Information

Formulate a Hypothesis

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Evaluating Hypotheses

A good hypothesis is one that can be tested.

Evaluate each of the following hypotheses as to whether or not they can be tested.

1. If the polar ice caps begin to melt, the amount of salt in the ocean water will change.

2. Dogs use mind control on their owners to be taken for walks and car rides.

Can be tested

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Steps in the Scientific Method

Step 4: Conduct an Experiment

An experiment is a controlled procedure designed to test your hypothesis.

When you conduct an experiment, you will manipulate variables. Variables are factors that affect the outcome of an experiment.

It is important to manipulate only one variable at a time, so that you will be able to identify what is causing the outcome.

In many experiments, it is valuable to have a control, that is a standard for comparison.

Ask a Question

Gather Information

Formulate a Hypothesis

Conduct an Experiment

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Types of Variables

An independent variable is the variable that you control or change. In the ice cream example, the independent variable is the amount of ice cream I eat.

A dependent variable is the variable that you measure. In the ice cream example, the dependent variable is whether or not I get sick.

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Identifying the Parts of an Experiment

You are asked to study the effect of temperature on the volume of a balloon. The balloon’s size increases as it is warmed.

1. What is the independent variable?

2. What is the dependent variable?

3. What factor is held constant?

4. How would you construct a control?

the temperature

The amount of air in the balloon

the size of the balloon

Use an identical balloon kept at room temperature.Main Menu

Steps in the Scientific Method

Step 5: Record and Analyze Data

Once your experiment is complete, the results should be analyzed to determine if your data supports your hypothesis.

If your data does not support your hypothesis, you will need to revise or reject your hypothesis.

Ask a Question

Gather Information

Formulate a Hypothesis

Conduct an Experiment

Record and Analyze Data

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Steps in the Scientific Method

Step 6: Report Results

Before communicating the results of an experiment to others, you should repeat the experiment several times to make sure that the first results weren’t just an accident.

Ask a Question

Gather Information

Formulate a Hypothesis

Conduct an Experiment

Record and Analyze Data

Report Results

(Conclusion)

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Models

A model is a visual, verbal, and/or mathematical explanation of experimental data.

Scientists often create models to help them test hypothesis and/or make predictions.

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Uses of Models

Models help simulate behavior of larger or smaller objects.

Ex. Model airplane

Models help predict future events.

Ex. Computer model of a storm

Models help us visualize objects.

Ex. Architectural model

Models can be used to explain structure and process.

Ex. Molecular model

Models provide experiences that might be dangerous or unavailable.

Ex. Flight SimulatorMain Menu

Theory

A theory is an explanation that has been supported by many, many experiments. All theories are subject to new experimental data and can be modified.

Example: Atomic Theory

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Scientific Law

A scientific law is a concise statement that summarizes the results of a broad variety of observations and experiments and is generally accepted as true.

A law may be in words or in mathematical form.

Ex. E=mc2Main Menu

States of Matter

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Matter exists in many different forms, and it can be classified in many different ways.

One way that matter can be classified is according to its physical state.

The three most common states of matter are solids, liquids, and gases.

Scientists recognize a fourth state of matter called plasma, but it does not occur naturally on Earth except in the form of lightning bolts.

Properties Commonly Used to Describe Solids, Liquids and Gases

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Fluidity – the ability of a substance to flow and therefore conform to the outline of its container.

Compressibility – the ability of a substance to be pressed together or compacted, thereby reducing the volume of the substance without changing its mass.

Rigidity – the property of a substance that describes the inability of an object to change shape, inflexibility or stiffness of a substance.

Properties of Solids

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The particles in a solid:

• are packed very close together.• are held together with strong intermolecular

forces or bonds• vibrate slowly in place

Solids:• have a definite shape• maintain their shape. This means they are rigid.• have a definite volume.• are incompressible• are relatively dense

Properties of Liquids

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The particles in a liquid: • are close together with some

intermolecular forces.• are able to move (slide past each other), but

movement is limited by intermolecular forces.

Liquids:• do not have a definite shape. • have a definite volume.• flow and fill the bottom of a container. This

means they are not rigid.• Are difficult to compress because there a quite a

low of particles in a small volume.

Properties of Gases

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The particles in a gas: • are far apart• are free to move in all directions• Have very weak intermolecular forces of

attraction

Gases:• do not have a definite shape. • flow and expand to fill any container. • are easily compressed• are often low density as there are not many

particles in a large space.

Properties and Changes in Matter

•Matter can be described in many different ways.

•One way matter can be described is according to its chemical and physical properties.

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PhysicalProperties

Chemical Properties

Properties that can be observed or measured without causing change to the substance’s composition.

Properties that relate to a substance’s ability to undergo changes to its composition.

Example: Magnesium Ribbon is silvery-white and is very light.

Example:

Magnesium burns in air to produce magnesium oxide.

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Classify each of the following as either a chemical or physical property.

1. Water boils at 100ºC. Physical

2. Wood is flammable.Chemical

3. Aluminum has a low density.Physical

4. Iron rusts in a damp environment.Chemical

5. Gasoline burns in the presence of oxygen.Chemical Main

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EXTENSIVEINTENSIVEProperties that do NOT depend on the sample size.

Properties that DO depend on the sample size.

Examples:DensityMelting PointMalleability

Examples:MassVolume

Another way of separating kinds of physical properties is to think about whether or not the size of the sample would affect a particular property.

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Classify each of the following as either an intensive or an extensive physical property.

1. Boiling Point. Intensive

2. VolumeExtensive

3. DensityIntensive

4. MassExtensive

5. MalleabilityIntensive Main

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Physical Changes

• Changes that do not result in the production of a new substance are known as physical changes

• The chemical composition is not changed during a physical change.

• Examplesfolding paper

melting butterdissolving salt in water Main

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Chemical Changes

• Changes in which one or more substances are converted into different substances with different chemical and physical properties.

• Chemical changes are also called chemical reactions.

• ExamplesBurning PaperReacting Acid with water

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Indications of a Chemical Change

• Formation of a gas (bubbling)

• Change in energy Endothermic – energy is absorbed,

surroundings get cold

Exothermic – energy is released, surroundings get warm

• Production of a precipitate

• Change in color or odorMain Menu

Classify each of the following as either a chemical change or a physical change.

1. Crushing an aluminum canphysical

2. Silver tarnishingchemical

3. A metal chair rustschemical

4. Dissolving sugar in waterphysical

5. Water freezing and forming icephysical Main

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Law of Conservation of Mass

• During a chemical change, the amount of matter present before the reaction is equal to the amount of matter after the reaction.

• In ordinary chemical reactions, matter can change forms, but it cannot be created or destroyed.

• This is known as the Law of Conservation of Mass. Main

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Identifying Reactants and Products

• The reactants are the chemicals present before a chemical reaction.

• The products are the chemical that are present after a chemical reaction.

• Reactants → Products

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Identifying Reactants and Products

Examine the following chemical equation in which sodium metal and chlorine gas react to form solid sodium chloride.

2Na(s) + Cl2(g) → 2NaCl(s)

Identify the reactant(s).Sodium (Na) and Chlorine (Cl2)

Identify the product(s).Sodium Chloride (NaCl) Main

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Note: The (s) and (g) indicate the physical state of each element substance.

Identifying Reactants and Products

Examine the reverse reaction in which solid sodium chloride is decomposed to form sodium metal and chlorine gas.

2NaCl(s) → 2Na(s) + Cl2(g)

Identify the reactant(s).Sodium Chloride(NaCl)

Identify the product(s).Sodium (Na) and Chlorine (Cl2) Main

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Law of Conservation of Mass

According to the law of conservation of mass, the total mass of the reactants of a chemical reaction must be equal to the total mass of the products present after a chemical reaction.

If the mass of all of the reactants and products except one are known, the law of conservation of mass can be used to calculate the mass of the other substance.

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Law of Conservation of Mass

Hydrogen reacts with oxygen according to the following reaction to produce water.

2H2 + O2 2H2O

How many grams of water will be produced if 4.0 g of hydrogen reacts with 32.0 g of oxygen?4.0 g + 32.0 g = 36.0 g

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Law of Conservation of Mass

Use the illustration below to determine the amount of zinc produced.

The amount of zinc produced is 64 g + 192 g = 152 g + ? Ans. 104 g

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Energy

Energy is the capacity for doing work or supplying heat.

There are many different kinds of energy present in the universe: electrical, light, sound, heat, nuclear, solar, and chemical for example.

The SI unit for energy is the joule (J).

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Energy

Many forms of energy can be classified under two larger categories of energy.

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Potential energy is stored energy. It is energy due to position or composition.

Kinetic energy is the energy of motion. The kinetic energy of a substance depends on the mass and velocity of the substance.

Law of Conservation of Energy

The law of conservation of energy states that energy cannot be created nor destroyed. It can however, be converted from one form to another.

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Law of Conservation of Energy

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The nuclear energy produced when hydrogen nuclei fuse into helium nuclei in the sun’s core is converted to

solar energy in the form of electromagnetic radiation. This solar energy travels from the sun through the vacuum of space and reaches the earth. This solar energy is converted to

Law of Conservation of Energy

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chemical energy. Plants convert the solar energy into chemical energy in the form of carbon compounds (sugars) through the process of photosynthesis. Dead plants are compressed and over time are converted to hydrocarbons which contain high energy bonds. The chemical energy from the coal is converted to

electrical energy. The electrical energy can be used to power things like your television set. The electrical energy is converted to heat, light, and sound.

Endothermic vs. Exothermic Reactions

Endothermic Reaction

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Exothermic Reaction

Reaction Progress

R

PReaction Progress

R

P

There is an overall absorption of energy.

There is an overall release of energy.

CH4 + 2O2 CO2 + 2H2O + energy2NaCl + energy 2Na + Cl2

Classify each of the following as endothermic or exothermic.

1. The products have more potential energy than the reactantsendothermic

2. When two chemicals are mixed in a beaker, the beaker gets warm.exothermic

3. boiling waterendothermic

4. H2 + I2 + energy → 2HIendothermic Main

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Classifications of Matter

Matter is anything that has mass and volume

Matter can be classified in several different ways.

Two common ways to classify matter are uniformity and ability to be broken down into simpler substances.

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HeterogeneousHomogeneousHomogeneous materials are uniform throughout.

Heterogeneous materials are not uniform throughout.The individual components are often visible.Heterogeneous materials often settle upon standing.

Examples:elementscompoundssolutions alloys

Examples:tossed saladbowl of raisin bran

Homogeneous vs. Heterogeneous

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Classify each of the following as homogeneous or heterogeneous.

1. Crunchy peanut butterheterogeneous

2. Paintheterogeneous

3. Steelhomogeneous

4. 3% hydrogen peroxide solutionhomogeneous

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Elements• Elements are pure substances that are made of only one type of atom.

• Elements are homogeneous.

• Elements cannot be separated into simpler substances by ordinary chemical or physical means.

• The known elements are listed on the periodic table.

• Chemical symbols are used to represent the elements. Ex. C, H, N

Compounds• Compounds are pure substances that are made of more than one type of atom chemically combined.

• Compunds are homogeneous.

• The properties of a compound are different from those of the elements from which it is made.

• Compounds can be broken down into their elements by chemical means.

• The elements making up a compound are always combined in the same ratio.

• Chemical formulas are used to represent compounds. Ex. NaCl, C12H22O11, H2O, CO2

Mixtures• Mixtures are physical combinations of two or more kinds of matter, each of which retains its own identity and properties.

• Mixtures can be homogeneous or heterogeneous.

• Homogeneous mixtures are called solutions. Examples include alloys, salt water, pure air

• Mixtures can be separated into simpler substances by physical means. Ex. Distillation, filtration, chromatography.

• Different mixtures of the same substance can have different compositions.

Classify each of the following as elements, compounds or mixtures.

1. spaghetti saucemixture

2. table sugarcompound

3. river watermixture

4. nitrogen gaselement

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NO

Matter

Is it uniform throughout?

NO

NO

YES

YES

YES

Solution

Homogeneous

Does it have a variable composition?

Heterogeneous Mixture

Pure Substance

Can it be separated into simpler substances?

Element Compound

Introduction to the Periodic Table

The periodic table is a tool that organizes the known chemical elements according to trends in their chemical and physical properties Main

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Element Squares

Atomic Number

Chemical Symbol

Element Name

Atomic Mass

14

Si28.086

Silicon

The element squares on the periodic table provide important information about each element.

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Use your periodic table to complete the following table.

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Element Name

Chemical Symbol

Atomic Number

Atomic Mass

Hydrogen

Cu

9

H 1 1.008

Copper 29 63.546

Fluorine F 18.988

Solid, Liquid or Gas?

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Some periodic table allow determination of the phase of the elements under standard conditions by coloring the element symbol differently for each phase.

How does the periodic table in the classroom indicate whether a substance is a solid, liquid, or gas?

The chemical symbols for the solids are written in black. The chemical symbols for the gases are written in red.The chemical symbols for the liquids are written in blue.

Solid, Liquid or Gas?

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Are most of the elements solids, liquids or gases?Solids

Which elements exist as liquids at room temperature?

Bromine and Mercury

Which elements exist as gases at room temperature?Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Helium, Neon, Argon, Krypton, Xenon and Radon

Arrangement of the Periodic Table

The elements in the periodic table are arranged in order of increasing atomic number. Main

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Arrangement of the Periodic Table

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The columns of elements in the periodic table are called groups or families.

Elements with the same family have similar chemical properties.

How many groups of elements are there in the periodic table?18

Arrangement of the Periodic Table

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Each row of elements in the periodic table is called a period.

The elements within the same period are not alike in properties.

How many periods of elements are there in the periodic table?7

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Properties of Metals, Nonmetals and Metalloids

Metals are shiny, metallic, and good conductors of electricity.

Nonmetals are dull in appearance, brittle, and do not conduct electricity.

Metalloids tend to be brittle and semiconductors of electricity.. Main

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USE YOUR PERIODIC TABLE TO COMPLETE THE FOLLOWING TABLE TABLE.

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Element Name

Chemical Symbol

Group Number

Period Number

Solid, Liquid or

Gas?

Metal, Nonmetal or Metalloid?

Strontium

Ne

14 3

Sr 2 5 Solid MetalNeon 18 2 Gas Nonmetal

Silicon Si Solid Metalloid