1. Physical and Chemical Changes
Matter
Physical and Chemical Changes
Pure Substances
Mixtures
States of Matter

2. Chemistry
The study of the composition, structure, and properties of matter and the changes it undergoes.
We, the Chemist, ask…
What is that made of?
How does that behave when you change environmental conditions?

3. Everything that has mass and volume is called matter.
What is matter?
Everything that has mass and volume is called matter.
Basic definition of matter.

4. Weight – depends on gravity – You weigh less on the moon than you do on earth
Mass – stays the same no matter where you are

6. Solids
Particles of solids are tightly packed, vibrating about a fixed position.
Solids have a definite shape and a definite volume.

7. Liquids
Particles of liquids are tightly packed, but are far enough apart to slide over one another.
Liquids have an indefinite shape and a definite volume.

8. Gases
Particles of gases are very far apart and move freely.
Gases have an indefinite shape and an indefinite volume.

9. Fluids
Gases and liquids
Contain particles that slide past each other

10. Physical Properties Physical properties are observable Examples are:
Mass
Volume
Density
Melting point
Boiling point
Hardness,
Color
Physical State – solid, liquid, or gas

11. Physical Properties Help ID Substances!
A physical property can be used to identify a substance – shape, color, odor, texture
Example: What is…
Round
Orange
Smells rubbery
Bounces
A Basketball!!

12. Chemical Properties
Chemical properties are related to the elements that make up a substance.
Chemical properties can only be observed as the object is changing
Examples:
Flammability
Reactivity
Toxicity

13. Intensive and Extensive Properties
Physical and chemical properties may be intensive or extensive.

14. What are intensive properties?
Intensive properties such as density, color, and boiling point do not depend on the size of the sample of matter.

15. What are extensive properties?
Extensive properties such as mass and volume do depend on the quantity of the sample.

16. Physical Change A change that produces a different
appearance of the substance but does not
change the composition of the substance
Examples: phase changes, dissolving, cutting paper, mechanical weathering, mixing
Physical changes are characterized by the following:

17. Chemical Change
A process that causes a change in the composition of the substance.
Examples: burning, rusting, baking, decomposing, souring milk, chemical weathering, digesting
Definition of chemical change.

18. Is iron transforming into rust a physical or chemical change
Does the substance change composition or just change appearance?

19. The color of sulfur is yellow..
Physical
Chemical
Does the substance change composition or just change appearance?

20. Dynamite explodes to form a mixture of gases
Physical
Chemical
Does the substance change composition or just change appearance?

21. Aluminum melts at 933 K Physical Chemical
Does the substance change composition or just change appearance?

22. Plants use CO2 to make sugar
Physical
Chemical
Does the substance change composition or just change appearance?

23. Quantitative vs. Qualitative Observations
Quantitative observations – numerical observations; the mass of the object is 23g
Qualitative observations – non-numerical observations; the liquid is warm

24. Scientific Method
The Scientific method is a systematic way of gathering evidence to support ideas and theories that help explain the natural world around us.

25. Steps of the Scientific Method
Step 1: State the Problem
What are we trying to figure out?
It is usually stated as a question containing words like “How”, “Why”, and “What”
The problems that are investigated are found using observations

26. Steps of the Scientific Method
Step 2: Research & Hypothesis
A Hypothesis is a testable prediction based on research and observations.
The hypothesis is the experimenter’s idea of what will happen.
Before a hypothesis is formed, there must be prior research or observations taken to make a prediction about the problem.

27. Forming a Hypothesis
When an experimenter has an idea of what will occur, they will write this idea as an “If... then…” statement.
Examples:
If I place a plant in sunlight, then it will grow better.
If I eat a lot of Twinkies, then I will gain a lot of weight.
A hypothesis MUST BE TESTABLE

28. Steps of the Scientific Method
Step 3: The Experiment
In order to test the hypothesis, an experiment must be conducted.
Consists of a list of materials and the procedure (steps of the experiment)
Experiments must be reproducible so other scientist can try them for themselves.
There are four specific parts to an experiment.

29. The Parts of an Experiment
Independent Variable
Also called the manipulated or controlled variable
What the experimenter controls or changes during the experiment to test the hypothesis
Dependent Variable
Also called the measured variable
What is measured during the experiment as the independent variable is changed

30. The Parts of an Experiment
Constants
Everything else in the experiment besides the variables
Held the same to make sure only the independent variable is affecting results
Control
A standard for comparison
Usually a trial of the experiment where the independent variable is totally absent

31. Steps of the Scientific Method
Step 4: Data Analysis
After the experiment has been conducted, data must be organized to make a conclusion
Data should first be organized in a data table.
Then, data can be visually organized using a graph in order to more easily form a conclusion

32. Steps of the Scientific Method
Step 5: Making a Conclusion
After the experiment has been completed, a conclusion must be formed.
Every conclusion must give evidence for the new idea or outcome.
It should contain the following:
Restatement of the Hypothesis
Brief description of lab organization
Comment on the data collected
Statement of the trend or pattern in the data collected
Statement discussing whether your hypothesis was accepted or rejected and what you can do further.

33. Scientific Method
Theory: a broad-based interpretation of nature that helps to explain a large number of observations.
A theory helps to unify our understanding of nature.
A theory is generally accepted by all scientists.
If a conflicting observation is found, the theory must be either modified or discarded.

34. Matter
Matter can be identified as either an element, compound, or a mixture.

35. Matter
Pure Substance
Element
Compound
Mixture
Homogeneous
Solution
Colloid
Heterogeneous

36. Characteristics of Pure Substances
Fixed composition
Cannot be separated into simpler substances by physical methods (physical changes)
Can only be changed in identity and properties by chemical methods
Properties do not vary
Basic characteristics of pure substance:

37. What is a pure substance?
Elements
Cannot be decomposed into simpler substances by chemical changes
Ex. Na, Pb, Ca
Compounds
Can be decomposed into simpler substances by chemical changes, always in a definite ratio
Ex. H2O, HCl, C6H12O6
The two categories of pure chemical substances.

38. Characteristics of Mixtures
Two or more substances that are not chemically combined.
Variable composition
Components retain their characteristic properties
May be separated into pure substances by physical methods
Mixtures of different compositions may have widely different properties
Basic identification of a mixture.

39. Homogenous Mixtures
Homogenous mixtures look the same throughout but can be separated by physical means (boil, decanter, distill, centrifuge)

40. What are solutions?
Solutions are homogenous mixtures that do not scatter light. These mixtures are created when something is completely dissolved in pure water. Therefore, they are easily separated by distillation or evaporation.
Examples: sugar water, salt water

41. What are colloids?
Colloids are homogeneous mixtures that scatter light (Tyndall effect). They can be described as a substance trapped inside another substance. For example: air trapped inside the fat molecules in whipped cream, milk, fog
Brainstorm more ideas of colloids: fog, egg merangue, jello, smoke, etc.

42. Heterogenous Mixtures
Do not have same composition throughout
Components are distinguishable
Easily separated by physical means
Examples: fruit salad, vegetable soup, sand, gravel
Brainstorm more examples of heterogenous mixtures.

44. Sugar water is considered a _________________
Heterogeneous mixture
Homogeneous mixture

45. Italian dressing is a/an _______________
element
compound
Heterogeneous mixture
Homogeneous mixture

46. Carbon dioxide is a/an _______________
element
compound
Heterogeneous mixture
Homogeneous mixture

47. Salt water is a/an _________________
element
compound
Heterogeneous mixture
Homogeneous mixture

48. Titanium is a/an ______________
element
compound
Heterogeneous mixture
Homogeneous mixture

49. Lemonade is a/an __________________
element
compound
solution
colloid

50. Mayonnaise is a/an __________________
element
compound
solutions
colloid