A Mad Scientist’s Chemistry Presentation

A Mad Scientist’s Chemistry PresentationCHEMISTRY TAKS

SCIENTIFIC METHOD• Conducts lab and field work in a SAFE

manner…• Environmentally and Ethically sensitive• Watch for questions that support unsafe

practices (COMMON SENSE)• Anticipate questions on disposal

Planning, Implementing, Collecting

• If given a problem, can you make a plan? • What is the problem?• What are possible solutions? (Hypothesis)• What steps could you take to get your

answers.

Organize, Analyze, Evaluate

• If given a set of facts, can you organize, analyze, and evaluate the data.

• Organize by “concept mapping”• What is the original question? • Analyze what you were given to answer the

question.

Make Inferences• Be able to read charts and determine trends.• If given a brief statement, identify key points first

and then relationships.• Is the trend up, down, etc.?• Concept mapping (THINKING MAPS) may clear the

question for you.

Critical Thinking Steps:• What is the question?• What data, information is provided?

Consider concept mapping.• Is the question simply a “fact question” or

is a conclusion called for?

A “fact” question…• What is the density of a 15 gram sample if it

occupies 5 cubic centimeters?• A. 2 grams/cc• B. 3 grams/cc• C. 5 grams/cc• D. 15 grams/cc

• Remember: formula sheets is provided!

Begin with “the question”

• You should be able to answer the question based on FACTS.

• Avoid “opinions”. An “opinion” answer on the test is USUALLY WRONG!

• Example: Which brand of toothpaste tastes best? TASTE is an OPINION.

Develop a HYPOTHESIS• What do you think the answer will be?• What have you seen in the past?• What does your library research say?• What are possible ways to answer your

question?

Develop a procedure• Write down how you will perform your test.• What equipment will you need?• What steps will be followed?• What safety issues are involved?• How will you collect and record your data?

Control your “variables”• What is a “variable”?• In this case:….

– Grain size and type of sugar– Original water temperature– Amount of tea in the mixture– Rate of stirring, etc.

Perform the Experiment• Follow the procedures you have

developed.• Keep accurate records of all results AND

OBSERVATIONS!• USE PROPER SAFETY PROCEDURES!

Interpret (EVALUATE) your results

• What kind of results did you get?• Did your results agree with your Hypothesis? • If not, why not?

– Did you make a mistake in your procedure? – Should you modify either your original Hypothesis or

your procedure?

Question Example?• The English physician Ronald Ross dedicated his

career to the investigation of malaria and how it spread. Ross knew that a parasite called Plasmodium was always found in the blood of people infected with malaria.

• People had long thought that malaria was a result of breathing “bad air”. Ross, however, thought that mosquitoes spread malaria from person to person. Which of these could BEST have helped Ross determine whether mosquitoes were involved in the spread of malaria?

Possible Answers• A. Observing wild mosquitoes for signs of malaria.• B. Injecting mosquitoes with Plasmodium.• C. Examining wild mosquitoes to see whether their tissues

contain Plasmodium.• D. Determine whether animals such as cows carry

Plasmodium in their blood.

Selecting the BEST answer…

What is Ross’s question?

• Are mosquitoes involved in the spread of malaria?

• Has he already made observations?– Yes, Plasmodium is seen in people infected by malaria.

•Can any be eliminated?

•Which answers use the same words and phrases, as the question?

•Now, which is the BEST answer?

Answer• C. Examining wild mosquitoes to see whether their

tissues contain Plasmodium.

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The Mad Scientist

TAKS OBJECTIVE 4• The student will demonstrate an

understanding of the structure and properties of matter.– investigate and identify properties of fluids

including density, viscosity, and buoyancy;– Relate the chemical behavior of element

including bonding, to its placement on the periodic table;

– Classify samples of matter from everyday life as being elements compounds, or mixtures

OBJECTIVE 4 continued• Distinguish between physical and chemical changes in matter

such as oxidation, digestion, changes in states, and stages in the rock cycle;

• Investigate and identify the law of conservation of mass• Relate the structure of water to its function as the universal

solvent;

• Relate the concentration of ions in a solution to physical and chemical properties such as pH, electrolytic behavior, and reactivity;

• Demonstrate how various factors influence solubility including temperature, pressure, and nature of the solute and solvent

WHAT IS MATTER?• Anything that has matter and takes up space.

– Element – building blocks of matter, cannot be broken down into simpler substances by a chemical REACTION.

– Compound – made up of two or more elements that are CHEMICALLY combined.

– Mixture – made up of two or more substances that can be broken down PHYSICALLY

THE ATOM•  

 

PROTONS

NEUTRON

ELECTRONS

ENERGY LEVEL

Properties of metals, nonmetals, and

metalloids METAL nonmetals METALLOIDS

shiny Mostly dull Vary in ability to conduct electricity

Malleable brittle Used to make semiconductorsConduct under certain conditions

ductile Poor conductors

Good conductors of heat & electricity

Many gases at room temperature

Most are solids at room temperature

Valence electrons• Electrons in the outermost energy level• Electrons involved in bonding

Li +

++

s2p1

↑↓ ↑

ATOM vs ION

● Ca ● Ca 2+ + 2e- Calcium atom Calcium ion 2 electrons20 + 20 +20 - 18 -

Net chg = 0 Net chg = 2+

Let’s tie this into the periodic table

Group number 1 2 13 14 15 16 17 18

# valence e- 1 2 3 4 5 6 7 8

Gain/lose e- Lose 1

Lose 2

Lose 3

Gain/lose +4/ -4

Gain 3

Gain 2

Gain 1

0

Chg of ion +1 +2 +3 +4 -4

-3 -2 -1 0

He: exception b/c it only has two electrons

Classifying mattermatter

Physically separated?no yes

Pure substance

Breakdown chemically?no

element compound

yes

mixture

Look the same?no ye

s

heterogeneous homogeneous

solution

Three types of Bonds• Ionic – rxn between oppositely

charged particles

• Electrons are transferred

– Covalent – nonmetals

–Electrons are shared

What about Bonding• Ionic – metal/nonmetal• Or between charged ions

Mn Mn2+ S2-S

IONIC BONDING• Transfers electrons:

Na + 2s22p6

Cl- 3s23p6

Covalent Bonding

COVALENT BONDS

• Examples of hydride compounds of the above elements (covalent bonds with hydrogen:

•

Covalent Bonding

METALLIC BONDS• Force that holds atoms together in a substance.

• Metallic bonding is possible because in many cases the outer most electron shell of each metal atoms overlaps with a large number of neighboring atoms.

• It is often said they have a sea of electrons.

Indications of a Chemical Change

1. Change in color2. Change in temperature3. ppt formed4. Formation of a gas5. Light given off6. New substance

Chemical/Physical Changes

• Physical change – does not change the composition – Cutting wood, melting ice, boiling water

• Chemical change – creates a new substance– Digestion food, grass growing

Now it’s your turn….

• Two steel plates can be joined by a process called arc welding. In this process, tiny droplets of molten metal are deposited on the joint between the plates. The droplets then cool and harden, joining the plates together.

• Many metals will react with oxygen when they are exposed to the high temperatures of arc welding. Therefore, the droplets of molten metal are often shielded from oxygen in the surrounding air by a layer of argon gas.

• Why would argon gas be a more suitable shield for arc welding than hydrogen gas?

– A. Unlike hydrogen, argon is a nonmetal– B. Unlike hydrogen, argon is an inert gas– C. Argon has a larger atomic radius than hydrogen does– D Argon has a greater atomic mass than hydrogen does.

Question• Which best explains why sodium is more reactive than

magnesium?

– A. Sodium has only one valence electron, while magnesium has two

– B Sodium atoms typically have one more neutron than magnesium atoms do

– C Sodium forms ions with a charge of 2+, but magnesium forms ions with a charge of 1+

– D Sodium atoms tend to attract the electrons of other atoms more than magnesium atoms do

Question• Hydrogen and nitrogen gas react in a sealed container

kept at a constant temperature. The pressure in the container is less at the end of the reaction than at the beginning.

• 3H2(g) + N2(g) 2NH3(g)

– A there are fewer atoms at the end of the reaction than at the beginning.

– B There are fewer molecules at the end of the reaction than at the beginning.

– C The mass of the reactants is less than the mass of the products in the reaction

– D The volume of the reactants is less than the volume of the products in the reaction

Question• Scuba divers are exposed to greater pressure the deeper they

dive. Which is most likely to occur as a result of this increased pressure?

• A. Glucose will become much more soluble in divers’ cells

• B A high level of nitrogen gas will dissolve in divers’ bloodstream

• C Small bubbles of carbon dioxide will form in divers’ bloodstream

• D the amount of oxygen dissolved in divers’ cells will sharply decrease

Good Luck!

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