1. Chapter 2: matter and change

2. Properties of matter What do you see when you look at matter?
Properties used to describe matter can be classified as either:
Extensive
Intensive

3. Extensive vs. intensive properties
Extensive: Property that depends on the AMOUNT of matter in a sample
Mass ( measure of the amount of matter the object contains)
Volume (measure of space occupied by an object)
Length
Intensive: property that depends on the TYPE of matter in the sample, not the AMOUNT.
Surface type
Hardness, softness
Density

4. Identifying substances
SUBSTANCE: matter that has a uniform and definite composition, ex: gold, copper
Every sample of a given substance has an identical intensive property due to the fact that every sample has the same composition
Look at Gold vs Copper properties
PHYSICAL PROPERTY
A quality or condition of a substance that can be observed or measured without changing the substance’s composition
Hardness, color, conductivity, malleability, boiling/melting point,

5. True or False?? A liquid conforms to its container.
Liquids take the shape of their container
A solid has a definite shape but changeable volume.
FALSE
Solids have definite shape AND volume

6. States of matter Three possible physical states of matter:
1. Solid: form of matter that has definite shape and volume
Does Not depend on shape of container
Particles Packed closely together
2. Liquid: indefinite shape, definite volume
Particles not rigidly held in place and are less closely packed than solid
Takes shape of container
3. Gas: form of matter that takes both the shape and volume of its container
Particles of gas are far apart
GAS vs VAPOR

7. What’s in the beaker?? C. A. B.

8. Physical Changes
During a physical change, some properties of the material change, but the composition of the material does not change
Look at Gallium below (or pg 42 in book)
Words used to describe physical change: boil, freeze, split, grind
What are some other words used to describe physical change?
Physical changes can be classified as either reversible or irreversible:
Freeze vs. Split

9. 2.2 Mixtures

10. Remember: A pure substance has a uniform and unchanging composition
Most everyday matter occurs as mixtures—or a combination of two or more substances
What happens when 2 or more substances are combined?

11. Classifying mixtures Mixture: physical blend of two or more components
Some can be easier to identify than others: Chicken noodle soup vs. air
Based on the distribution of their components, mixtures can be classified as either heterogeneous or homogeneous.

12. Are these both mixtures??

13. Heterogeneous vs homogeneous
Does not blend smoothly
Composition is not uniform throughout
Chicken noodle soup, may be more chicken in one spoonful than in the next

14. Heterogeneous vs homogeneous
Homogeneous AKA Solution
Composition is uniform throughout
Vinegar contains water and acetic acid
Can be either liquid (most are), gas (air), or solid (steel, made up of iron, chromium, and nickel) or a mixture

15. Homogenous Mixtures

16. Separating mixtures
Differences in physical properties can be used to separate mixtures
Filtration
Distillation
Crystallization
Sublimation
Chromatography

17. Separating mixtures Filtration
Separating a SOLID from LIQUID using porous barriers
Filtration can be used with heterogeneous mixtures
Uses:
Colander or coffee filter

18. Separating mixtures Distillation Used with homogenous mixtures
Based on different boiling points
Liquid is boiled to produce a vapor that is then condensed into a liquid (The substance that produces the vapor has the lowest boiling point)
Look at the distillation process on page 47

19. Separating mixtures Crystallization
Separation technique that results in the formation of pure solid particles of a substance from a solution containing dissolved substances

20. Separating mixtures Sublimation
Process during which a solid changes to a gas without melting (without going through the liquid phase)
Used to separate two solids present in a mixture when one solid sublimates but not the other

21. Separating mixtures Chromatography
Separates the components of a mixture based on the ability of each component to travel or be drawn across a surface of another material
Various components of the mixture spread through the paper at different rates

22. 2.3 Elements and compounds

23. Recap
So far we have discussed: Properties of matter- Extensive and Intensive States of matter- solid, liquid, gas Physical Changes Mixtures- homogeneous vs heterogeneous Separating mixtures- filtration, distillation, crystallization, sublimation, and chromatography

24. Distinguishing elements and compounds
Element: simplest form of matter that has a unique set of properties
Oxygen and hydrogen most commonly known
Compound: substance that contains two or more elements chemically combined in a fixed proportion
Carbon+Oxygen+Hydrogen combined to make sucrose
In every sucrose sample there are equal parts of carbon and oxygen particles and twice as many hydrogen
What is the difference between a compound and an element?
A compound can be broken down into simpler substances by chemical means, elements cannot be broken down.

25. compounds
Physical methods that we can use to separate a mixture can not be used to break down a compound. For example: when you boil water, the liquid becomes steam or vapor. But it is still water NOT separate Oxygen and Hydrogen.
So….How do you break down a compound?? Can it be done??
YES!! But a CHEMICAL CHANGE must occur. A chemical change is a change that produces matter with a different composition than the original matter.
This can be done through heating or through an electric current
Properties of compounds are different than the properties of the elements that make up the compound.
Sugar: Sweet, white solid but Carbon: black, tasteless

26. Substance or Mixture?? How can we tell?
Distinguishing by appearance alone can be difficult because homogeneous mixtures and homogenous substances both appear to contain only one kind of matter. In general, if the composition of a material is fixed, the material is a substance. If the composition of a material varies, it is a mixture. Look at Figure 2.11 on page 50

27. Symbols and formulas Chemical symbols are used to represent elements.
Chemical formulas represent compounds.
Why do we use these??? Common names do not provide information about the chemical composition.
The symbols used today are based on a system developed by a Swedish chemist, Jons Jacob Berzelius, who based his symbols on the Latin names of the elements.
First Letter is always capitalized, second (if present) is lower case.
Some match their English name, if Latin and English are similar (Calcium: Ca)
Others match their Latin name (Sodium (natrium): Na)
The formulas use these symbols for shorthand when writing compounds
H2O: 2 parts hydrogen, 1 part oxygen in every water compound

28. 2.4 chemical reactions

29. Chemical change
What happens when your bike sits out in the rain for days?? (If your bike is made of iron)
It rusts! Or the compound iron oxide is formed.
Words that describe chemical change:
Burn, rot, rust, decompose, ferment, explode, corrode
Chemical Property: the ability of a substance to undergo a specific chemical change.
The ability for iron to rust is a chemical property
During a chemical change, the composition of matter always changes.
Chemical change can also be known as a chemical reaction, where one or more substances changes in to one or more NEW substances.
Reactant- Product

30. Was that a Chemical Change?
How do we know a chemical change has occurred? 4 clues:
1. transfer of energy
Heat released
2. change in color
Food browning when cooked
3. production of gas
4. formation of precipitate
Soap scum on a bathtub when sprayed with cleaner
Some chemical and physical changes look similar. Only way to know if a chemical change has occurred, is to test the composition of a sample before and after the change.

31. Conservation of mass
During any chemical reaction, the mass of the products is always equal to the mass of the reactants.
Think about firewood burning in a fire pit. (Must factor in gases released)
Note: Mass also remains constant for physical changes. 10g of ice melts to 10g of liquid.
Law of Conservation of Mass: states in any physical change or chemical reaction, mass is conserved.
Mass of reactants=Mass of products

32. Conservation of mass numeric problem
In an experiment, g of red mercury (II) oxide powder is placed in an open flask and heated until it is converted to liquid mercury and oxygen gas. The liquid mercury has a mass of 9.26 g. What is the mass of oxygen formed in the reaction? Identify the “known” values. What is unknown? Solve for the unknown. ** Remember: Law of conservation of mass: Massreactants = Massproducts

33. Chemical vs Physical
Look at Figure 2.13 in book