Matter and Change

What is Chemistry All About?

How does this photo illustrate what chemistry is all about??

 Chemical reactions of rusting/weathering/maybe a fire in the fireplace  Physical states of water  Different types of materials: glass, wood, living material, brick, snow

The Study of Matter and Change

What is Matter?  Anything that has mass and takes up space (volume) Not Matter  Light      Energy Emotions or Feelings Thoughts Electricity Sound

Pure Science Vs Applied Science

 Pure Science: For the sake of the knowledge  Studying butterflies just to know more  Researcher lives on a remote island to daily study the jungle trees  Studying ape behavior  Applied Science: Using science to solve a particular problem  Scientist studying corn in fields to increase the yield for farmers  Scientist searching for a cancer cure

Why is Pure Research Important?

 A Base of knowledge when needed  Keeps us current  General not specific and possible commercial  Accidental Discoveries

Technology

 Application of Science for human benefit  Good and Bad  Nuclear Technology  Good: Energy Bad: Waste  Computer Technology  Good: Communication Bad: Wasted Time

Chemistry is traditionally broken into branches that focus on specific areas such as

– – – – – – – – : – – Organic chemistry Inorganic chemistry Physical chemistry Analytical chemistry Biochemistry Environmental chemistry Industrial chemistry Polymer chemistry Theoretical chemistry Thermochemistry

This Class



HS General Chemistry is Inorganic

Inorganic: the study of non-carbon based compounds  Organic Chemistry: Study of matter that contains carbon

The Scientific Method

 The

scientific method

is a systematic approach used in scientific study, whether it is chemistry, physics, biology, or another science.

 To solve problems  Not a set of rigid steps  It is an organized process used by scientists to do research, and provides methods for scientists to verify the work of others.

Observations

 Gathering Information (Data) using the five senses  No trivial or unimportant observations  Don’t make inferences or assumptions when you observe –

Qualitative data

is obtained through observations that describe color, smell, shape, or some other physical characteristic that is related to the five senses.

–

Quantitative data

is obtained from numerical observations that describe how much, how little, how big or how fast.

    

Controlled Experiment

A test of a hypothesis Making observations under controlled conditions Where only one variable at a time is changed Systematic approach to test a hypothesis Parts of An Experiment  Variables: A condition changed in an experiment      Independent Dependent Constants: any factor not changed in an experiment Control: Group/set up that has no changes made to it Conclusion: A judgment based on the observations made in a controlled experiment

Independent Variable

 Changed by the experimenter  Allowed to change  The Cause in Cause and Effect  Manipulated Variable  Happens First  The water’s temperature increased as more heat applied. was  The temperature of the solid caused the density of the solid to change  An increase in phosphorous helped the plants to grow taller.

Dependent Variable

 Changes in response to the change in the independent variable  Responding Variable  Happens second  The

boiling point

increased as salt was added to the water  The

hamster grew

two inches with an increase in the hormone.

Control

 A point of comparison in an experiment  The group that does NOT receive the treatment

Constants

 Specifics that remain the same between the control group and the experimental group  Only the independent variable should be changed by the experimenter Examples of Constants:

Conclusion

 A

conclusion

is a judgment based on the information obtained from the experiment

Hypothesis and Experiment

 Hypothesis: A tentative explanation of observations  A tentative answer  A statement to be tested by an experiment Example: If I give the fish more hormone then they will grow longer.  Experiment: The test of a hypothesis  A controlled set of steps to test a hypothesis

Theory Vs Hypothesis

 A theory is a hypothesis that has stood the test of repeated experiments  An explanation of results  Never proven  Can be disproven  All theories are hypotheses . (True)  All hypotheses can become theories. (True)  All hypotheses are theories. (False)

 

Experiment

Kate noticed that she could dissolve more sugar in the tea when it was warm than when it was ice cold. She wondered if this was true for all solids. She decided to design an experiment to see if water temperature effects how much salt can be dissolved. She chose table salt as her solid to test. She used water as her solvent.  Hypothesis: An increase in the temperature of the water will allow more salt to dissolve,       She placed 100 mL of water in each of 10 250 mL beakers. She cooled the water in beaker # 1 to 10 degrees C. The water in beaker #2 was 25 degrees C.

Beaker # 3 water was heated to 35 degrees C. Beaker # 4 water was heated to 45 degrees C. Beaker # 5 was heated to 55 degrees C.

 Beaker # 6 65 degrees C  Beaker # 7 75 degrees C  Beaker # 8 85 degrees C  Beaker # 9 95 degrees C  Beaker # 10 100 degrees C

 She added salt to each beaker while using a magnetic stirrer which provided constant and uniform stirring until no more salt would dissolve.  She measured and recorded the amount of salt that dissolved in each beaker.  Her data is shown below.

Data

Amount of water 100 mL

1

Temp of Water (degrees C)

10 7 8 9 10 2 3 4 5 6 25 35 45 55 65 75 85 95 100 39 40 40 40

Grams of salt dissolved

37 37 38 38 38 38

Identify the following

 Independent Variable  Dependent Variable  Control  Constants  Possible conclusion  Another hypothesis

Scientific Law Vs Theory

 Observable Fact  True: Always observed  No known exceptions  No explanation  Explanation  Tentative  Can be disproven

      

Development of a Theory

Start with an observation that evokes a question: Broth spoils when I leave it out for a couple of days. Why?

Using logic and previous knowledge, state a possible answer, called a

Hypothesis: Tiny organisms floating in the air must fall into the broth and start reproducing. Perform an experiment or Test: After boiling some broth, I divide it into two containers, one covered and one not covered. I place them on the table for two days and see if one spoils. Only the uncovered broth spoiled.

Then publish your findings in a peer-reviewed journal. Publication:

"Only broth that is exposed to the air after two days tended to spoil. The covered specimen did not."

Other scientists read about your experiment and try to duplicate it.

Verification: Every scientist who tries your experiment comes up with the same results. So they try other methods to make sure your experiment was measuring what it was supposed to. Again, they get the same results every time.

In time, and if experiments continue to support your hypothesis, it

becomes a Theory: Microorganisms from the air cause broth to spoil. Useful Prediction: If I leave food items open to the air, they will spoil. If I want to keep them from spoiling, I will keep them covered.

Chemistry is Central to our Lives

 Chemistry is about composition, structure, function, and interaction of matter  Everything has composition, structure, function, and interaction.

 All other sciences (biology, physics, geology, etc) have their basis in chemistry

Mass Vs Weight

Mass

  Not influenced by gravity Changes only when amount of matter changes  Kilograms or grams

Weight

   Affected by gravity W = mg g= 9.8 m/s 2

Your Mass

Earth

 M ass = 60 kg

Moon

   Gravity = 1/6 th Earth the gravity on Mass = 60 kg Not affected by gravity

Weight

Earth

    m = 60 kg W = mg W = (6o kg)(9.8m/s 2 ) W = 588 Newtons

Moon

     m = 60 kg W = mg g = 9.8m/s 2 /6 = 1.63 m/s 2 W = (60 kg)(1.63m/s 2 ) W = 98 Newtons

Environment with No Gravity

 Weight only would change  You would weigh less  Amount of Matter is not affected  Mass stays the same

Submicroscopic and Macroscopic

Submicroscopic

  Atomic Level What happens here determines the macroscopic

Macroscopic

  What we observe Determined by the submicroscopic (atomic)  Chemist are interested in how the atomic level determines the macroscopic

Substance is matter that has a definite composition. Also known as a chemical

Element

 One type of atom    Oxygen (O 2 ) Ozone (O 3 ) Copper

Compound

 Two or more types of atoms  Sodium chloride (table salt) NaCl   Ethyl alcohol H 2 O

Chance Discoveries

 Discoveries made by accident  Not trying to find an answer  Examples  Velcro   Penicillin Teflon   Chocolate Chip Cookies The Microwave Oven  Artificial Sweeteners  Curiosity Drives Discovery