1. Chapter 2: Matter and Change

2. Section 2.1 Properties of Matter
Objectives:
Identify properties of matter as extensive or intensive
Define physical property, and list several common physical properties of substances
Differentiate among three states of matter
Describe a physical change

3. Matter Matter is anything that has mass and takes up space Mass Volume
Measure of the amount of “stuff”
(or material) the object contains
Don’t not confuse mass with weight
Volume
Measure of the space occupied by the object

4. Describing Matter Understanding matter begins with observations…
What you observe when you look at a sample of matter is its properties
Properties are words that describe matter (adjectives)
Substance
Matter that has a uniform and definite composition

5. Describing Matter
Properties used to describe matter can be classified as:
Extensive – depends on the amount of matter in the sample
-Examples: Mass, volume, calories
Intensive – depends on the type of matter, not the amount present
- Examples: Hardness, density, boiling point

6. Describing Matter Properties of matter can also be classified as:
Physical properties – a property that can be observed and measured without changing the materials composition
Examples: color, hardness, melting point, boiling point
Chemical properties – a property that can only be observed by changing the composition of the material
Examples: ability to burn, decompose, ferment, react with other substances

7. States of Matter Three Main Phases
Look at the pictures at the bottom of your notes page:
Shape?
Volume?
“closeness” of molecules?
Three Main Phases

8. States of Matter There are 3 states of matter Solid Liquid Gas
Look at the pictures at the bottom of your notes page:
Shape?
Volume?
“closeness” of molecules?
There are 3 states of matter
Solid
Has a definite shape and volume
Particles are packed tightly together
Liquid
Has indefinite shape, takes shape of container, has definite volume
Particles are close together but are free to flow past one another
Gas
Takes both shape and volume of container
Particles are far apart and can move freely
Vapor – a substance that is currently a gas, but normally is a liquid at room temperature
(water gas? or water vapor?)

9. States of Matter
Three phases of matter

10. Physical versus Chemical Change
Physical Change
Changes the appearance of the substance without changing the composition of the material
Examples: boil, melt, cut, bend, split, crack
Can be both reversible or irreversible
Reversible changes involve a change from one state to another (boil, melt)
Irreversible – cutting hair, cracking an egg

11. Physical versus Chemical Change
Reversible physical changes

12. Physical versus Chemical Change
A change where a new form of matter is created
Examples – rust, burn, decompose, ferment

13. Section 2.2 Mixtures Objectives
Categorize a sample of matter as a substance or a mixture
Distinguish between homogeneous and heterogeneous samples of matter
Describe two ways that components of mixtures can be separated

14. Substance versus Mixture
Matter that has a uniform and definite composition
Mixture
A physical blend of two or more components. Mixtures have variable compositions

15. Classifying Mixtures Mixtures can be classified as: Heterogeneous
The mixture is not uniform in composition
Examples: gravel, soil, salad, chocolate chip cookie
Homogeneous
The mixture has a uniform composition throughout
Called solutions
Examples: iced-tea, salt water
Most are liquids, some gases (air), some solids (stainless steel)

16. Classifying Mixtures Phase?
The term phase is used to describe any part of a sample with uniform composition and properties
A homogeneous mixture consists of one phase
A heterogeneous mixture consists of two or more phases

17. Classifying Mixtures
Olive oil and vinegar are homogeneous mixtures. The substances in these mixtures are evenly distributed. When olive oil is mixed with vinegar, they form a heterogeneous mixture with two distinct phases

18. Separating Mixtures Some mixtures can be easily separated
Rocks and marbles, iron and sulfur (iron is magnetic)
Differences in physical properties are used to separate mixtures

19. Separating Mixtures Filtration
Separates a solid from a liquid in a heterogeneous mixture by size
Pasta in a colander
Water in a coffee filter

20. Separating Mixtures Distillation A way to separate homogenous mixtures
A liquid is boiled to produce vapor that is then condensed into a liquid

21. Separating Mixtures Distillation
What can you infer about the boiling points of the substances in the original mixture?

22. Section 2.3 Elements and Compounds
Objectives
Explain the differences between an element and a compound
Distinguish between a substance and a mixture
Identify the chemical symbol of elements and name elements given their symbol

23. Distinguishing Elements and Compounds
Substances
Elements
Simplest kind of matter
Cannot be broken down into anything simpler
All one kind of atom
Compound
Substance that contains 2 or more elements chemically combined in a fixed proportion
When broken down the pieces have completely different properties than the original compound

24. Distinguishing Compounds from Mixtures
Compound or Mixture?
Compound
Mixture
Made of one kind
of material
Made of more than
one kind of material
Made by a
chemical change
Made by a
physical change
Variable Composition
Definite Composition

25. Breaking down Compounds
Compounds can be broken down into simpler substances by chemical means, but elements can not
A chemical change is a change that produces matter with a different composition than the original matter
Example – sugar is composed of C, H, and O heating sugar will break it down into carbon and water vapor but the carbon will never be broken down further

26. Properties of Compounds
Compounds have very different properties than their component elements
Due to a chemical change the resulting compound has new and different properties
Example – sodium chloride
sodium is a soft gray metal
chlorine is a yellow-green poisonous gas
sodium chloride is …
table salt

27. Distinguishing Substances and Mixtures
If the composition of a material is fixed, the material is a substance
If the composition of a material varies, the material is a mixture
Examples
Premium, plus and regular gas –
Whole, 2%, 1% and skim milk –
Carbon dioxide – always 1 carbon for every 2 oxygen
mixtures
mixtures
compound

28. Classifying Matter: Pure substance mixture Is the composition uniform?
Can it be
separated by physical means?
Pure substance
mixture
Can it be decomposed by ordinary chemical means?
Is the composition uniform?
Homogeneous mixtures (air, sugar water, stainless steel)
Heterogeneous mixtures (granite, blood)
Compounds
(ex: Water,
NaCl, sucrose)
Elements
(ex: gold, aluminum,oxygen)

29. Symbols and Formulas Currently there are 117 elements
Elements have 1 or 2 letter symbols, and compounds have formulas
An elements first letter is always capitalized, if there is a second letter it is written lower case
C – Carbon
Ca – calcium
K – potassium
Au- gold

30. Symbols and Formulas
In formulas, subscripts are used to indicate relative proportions of the elements in the compound
Example
H2O
C12H22O11
This means that for every 2 Hydrogen atoms there is 1 Oxygen atom (Water)
This means that for every 12 Carbon atoms there are 22 Hydrogen atoms and 11 Oxygen atoms (starch)

31. Periodic Table of the Elements
Symbols and Formulas
Periodic Table of the Elements

32. Section 2.4 Chemical Reactions
Objectives
Describe what happens during a chemical change
Identify four possible clues that a chemical change has taken place
Apply the law of conservation of mass to chemical reactions

33. Chemical Changes Chemical property
The ability of a substance to undergo a specific chemical change is called a chemical property
Iron plus oxygen forms rust, so the ability to rust is a chemical property of iron
During a chemical change the composition of matter always changes
Remember – in a physical change – substances present before the change are the same substances present after the change although they are no longer physically blended

34. Chemical Changes Chemical changes are also called chemical reactions
During chemical reactions one or more substances are changed into new substances
Reactants –
Products –
The products will have new properties different form the reactants you started with
Materials you start with
Materials you end up with

35. Recognizing Chemical Changes
There are 4 clues that can serve as a guide to identify chemical changes
Energy – is absorbed or released (temperature change indicates transfer of energy)
Color change
Gas production (bubbles, fizzing, odor change, smoke)
Formation of a precipitate
Precipitate – a solid that forms and separates from solution (will not dissolve)
Only way to be sure that a chemical change has occurred is to test the composition of the sample before and after the change

36. Conservation of Mass During any chemical reaction…
The mass of the products is always equal to the mass of the reactants
All of the mass can always be accounted for
Law of Conservation of Mass
In any physical or chemical change, mass is conserved. Mass is neither created nor destroyed.