1. Foundations of Chemistry
Chapter 7
Material on Midterm

2. Essential Questions What is a substance?
How do atoms of different elements differ?
How do mixtures differ from substances?
How can you classify matter?
What are some physical properties of matter?
How are physical properties used to separate mixtures?
How can a change in energy affect the sate of matter?
What happens when something dissolves?
What is meant by conservation of mass?
What is a chemical property?
What are some signs of chemical change?
Why are chemical equations useful?
What are some factors that affect the rate of chemical reactions?

3. Check in Questions! FALSE TRUE
Move to the “true” or “false” side of the room based on your beliefs about the following statements
FALSE
TRUE
1. The atoms in all objects are the same
2. When wood burns, new materials form
3. The weight of a material never changes, regardless of where it is
4. You cannot always tell by an object’s appearance whether it is made of more than one type of atom
5. When you stir sugar into water, the sugar and water evenly mix
6. Boiling is one method used to separate parts of a mixture
7. Temperature can affect the rate at which chemical changes occur

4. 1-Classifying matter
We are made of matter
Matter is anything that has _______ and takes up ________
mass
space
Is it matter?
Toaster
Bowl of soup
Steam
Sound
Dust
Air
Heat
Flag
Bacteria
Light
An _______ is a small particle that is a building block of matter
atom

5. 1-Classifying matter
A ______________ is matter with composition that is always the same
Ex: Aluminum, water, oxygen, sugar
Two major types of substances
____________ are substances that consist of just one type of atom
Elements are arranged in the periodic table
substance
Elements

6. 1-Classifying matter
A substance is matter with composition that is always the same
_____________ are substances containing atoms of two or more different elements chemically bonded together
Atoms are always combined in the same way
Compounds are represented by chemical formulas
C and O are atom symbols
2 (subscript) tells you how many
Compounds

7. 1-Classifying matter Properties Compounds versus Elements
A compound will have different ______________ than the elements that make it up
properties

8. 1-Classifying matter What is a mixture?
A mixture is matter that can vary in composition
No chemical reaction
No compound formed
Each substance keeps its original identity
The Ratio of Components in a Mixture
No fixed ratio—not always the same

9. 1-Classifying matter Heterogeneous Homogeneous not evenly evenly
_______________________ Mixture
______________________ Mixture
Definition: type of mixture in which the individual substances are _________________ mixed
Definition: type of mixture in which the individual substance are ____________ mixed
Different samples of a given heterogeneous mixture can have different combinations of the same substance
Different samples of a given homogeneous mixture will have the same combinations of the same substances
Heterogeneous
Homogeneous
not evenly
evenly

10. Hide the LOOT in the VENT!
1-Classifying matter
Homogeneous mixtures are also known as _______________
Solutes dissolve into solvents
Dissolving means to form a solution by mixing ___________
solutions
evenly
Hide the LOOT in the VENT!

11. 1-Classifying matter Comparing Mixtures and Compounds elements both
Made up of elements, compounds, or ________
Made of _____________
_________________ in original properties of components
_____________ in original properties of components
Separated by ___________means
Separated by ___________ means
Formed using ____ ratio of components
Formed using a _____ ratio of components
elements
both
No change
Change
chemical
physical
any
set

12. 1-Classifying matter

13. Full sentences for full credit!
Writing Prompt #1 (of 3)
Write the answer on your green sheet.
Explain why a Reeses Peanut Butter Cup would be a heterogeneous mixture, the inside of a Reeses Pieces would be a homogeneous mixture.
Full sentences for full credit!

14. 2- Physical Properties
Physical properties are characteristics of matter that you can observe or measure without changing the identity of the matter
Density is the mass per unit volume of a substance. Lead is very dense, so it makes a good sinker for a fishing line
Thermal conductivity is the rate at which a substance transfers heat. Plastic foam is a poor conductor
State is the physical form of the substance, such as solid, liquid, or gas. Ice is water in the solid state
Malleability is the ability of a substance to be rolled or pounded into thin sheets. Aluminum can be rolled into sheets to make foil
Solubility is the ability of a substance to dissolve in another substance. Flavored drink mix dissolves in water.
Ductility is the ability of a substance to be pulled into a wire. Copper is often used to make wiring because it is so ductile

15. 2-Physical Properties Size-dependent properties
These are properties of matter that depend on the size or amount of matter
Examples: mass and volume
Size-independent properties
These are properties of matter that do not depend on the amount of matter present
Examples: melting point, boiling point, electrical and thermal conductivity, solubility, and density

16. 2-Physical Properties Matter and Mass and Weight
Mass is the amount of matter in an object
Size-dependent property
It is the same everywhere in the universe!
Weight is a measure of the gravitational force exerted on an object
The more mass, the more weight
Varies by its location in the universe

17. 2-Physical Properties Differences between Mass and Weight Mass Weight
Measure of amount of matter in an object
Measure of the gravitation force on an object
Always constant for an object no matter where it is
Varies depending on where the object is on the Earth or the universe
Measured using a balance (shown below)
Measured using a spring scale (shown at right)
Expressed in kilograms (kg), grams (g), and milligrams (mg)
Expressed in newtons (N)

18. 2-Physical Properties
Volume is the amount of space taken up, or occupied, by an object
Liquid volume
Often use units like the Liter (L) and milliliter (mL)
1000 mL = 1 L
Use a graduated cylinder to measure
Read along meniscus bottom
Meniscus is a curve at a liquid’s surface

19. 2-Physical Properties Volume of solids Regular shape—use a formula
Irregular shape—water displacement method
Measure water volume
Measure new volume with object
Find difference (subtract!)
VOLUME = LENGTH X WIDTH X HEIGHT

20. 2-Physical Properties Irregular volume guided practice
Initial: ____ mL
Final: ____ mL
Volume: ____ ____
Don’t forget units!
Irregular volume You try!
Initial: ___ ____ (units!)
Final: ___ ____ (units!)
Volume: ___ ___ (units!)
100 90 80
100 90 80

21. 2-Physical Properties Guided Practice
How will we do math problems in physical science?
4 steps
Write the formula
Show work
Solve
Check to see we have the right units!

22. 2-Physical Properties Guided Practice
Sample problem: What is the volume of a box that has a length of 5 cm, a width of 1 cm, and a height of 2 cm?
Step 1: Write the formula
Step 2: Identify the variables L: W: H:

23. 2-Physical Properties Guided Practice
Sample problem: What is the volume of a box that has a length of 5 cm, a width of 1 cm, and a height of 2 cm?
Step 3: Plug in variables and solve
Step 4: Unit check!
NO NAKED NUMBERS!!

24. 2-Physical Properties You try
Sample problem: What is the volume of a box that has a height of 10 cm, a width of 2 cm, and a length of 3 cm?
Step 1:
Step 2: L: W: H:
Step 3:
Step 4: Unit check!

25. Densities of Common Substances
2- Physical Properties
PING PONG
2 grams
Density
Describes the relationship between mass and volume
Density is the mass per unit volume of a substance
Density can help identify substances
Densities of Common Substances
SUBSTANCE
DENSITY (g/cm3)
Helium (gas)
Zinc (solid)
7.13
Oxygen (gas)
Silver (solid)
10.50
Water (liquid)
1.00
Lead (solid)
11.35
Pyrite (solid)
5.02
Mercury (liquid)
13.55
GOLF
46 grams

26. 2- Physical Properties Formula triangle
Cover what you want to solve for
If two variables are next to each other, then ×multiply×
If two variables are stacked, ÷ divide ÷
Units
Mass: grams
Volume:
Liquid/irregular: mL
Regular: cm3
Density
Liquid/irregular: g/mL
Regular: g/cm3

27. 2-Physical Properties Guided practice
Sample problem: What is the density of an object whose mass is 25g and whose volume is 10 cm3?
Step 1: Write the formula
Step 2: Identify variables

28. 2-Physical Properties Guided practice
Sample problem: What is the density of an object whose mass is 25g and whose volume is 10 cm3?
Step 3: Plug in variables and solve
Step 4: Unit check!

29. 2-Physical Properties You try
Sample problem: Suppose you have a lead ball whose mass is 454 g. What is the ball’s volume?
Step 1:
Step 2:
Step 3:
Step 4: Unit check!

30. 2-Physical Properties Combination problem:
You have a substance that has a mass of 96.6g. When you place it into a graduated cylinder, the water rises from 10 mL to 15 mL.
Find the volume of the substance
Find the density of the substance
You think it might be copper (density= 8.96 g/mL) or gold (density =19.32 g/mL). Which material is it?

31. 3-Physical Changes Physical Changes do not form new substances
A physical change is a change in size, shape, form, or state of matter in which the matter’s identity stays the same

32. 3-Physical Changes Matter and physical changes
Physical changes to not change the identity of the matter involved
Freezing water
Ice is still water
Sanding wood
Sawdust is still wood
Cutting a piece of paper
Paper scraps are still paper
Melting butter
Melted butter is still butter

33. 3-Physical Changes States of matter
Solids have very little energy and vibrate in place
Liquids have a little more energy and slide back and forth
Gases have the most energy and fly all over the place

34. 3-Physical Changes Changes in State of Matter
Adding thermal energy causes atoms in a substance to move faster
SolidLiquid • Liquid Gas
Removing thermal energy causes atoms in a substance to move slower
Gasliquid • LiquidSolid

35. 3-Physical Changes Conservation of Mass
During a physical change, the physical properties of matter change, but the particles are the same as those present before the change occurred
The mass before a physical change has to be the same as the mass after a physical change

36. 4-Chemical Properties and Changes
A chemical property is a characteristic of matter that can be observed as it changes to a different type of matter

37. 4-Chemical Properties and Changes
Flammability is the ability of a substance to burn
Reactivity is the ability of two or more substances to combine to form one or more new substances

38. 4-Chemical Properties and Changes
Physical versus Chemical properties
Physical Property
Chemical Property
Shape Bending an iron nail will change its shape
Reactivity An iron nail can react with oxygen in the air to form iron oxide (rust)
State Rubbing alcohol is a clear liquid at room temperature
Flammability Rubbing alcohol is able to burn easily

39. Full sentences for full credit!
Writing Prompt #2 (of 3)
Write the answer on your green sheet.
What is similar about physical and chemical properties? What is different?
Full sentences for full credit!

40. 4-Chemical Properties and Changes
Physical versus Chemical properties
How do you tell?
Chemical—substance changes into something new by observing property
Physical—does not change identity by observing property

41. 4-Chemical Properties and Changes
Chemical Changes and New Substances
A chemical change is a change in matter in which the substances that make up the matter change into other substances with new physical and chemical properties
Not the same as a chemical property!

42. 4-Chemical Properties and Changes
How do we know a chemical change is occurring?
Change in color or odor

43. 4-Chemical Properties and Changes
How do we know a chemical change is occurring?
Formation of a gas or bubbles (fizzing and foaming)
Sound or light being given off (change in energy)

44. 4-Chemical Properties and Changes
Physical versus Chemical Changes
How do I know which is which?
DID THE CHEMICAL COMPOSITION CHANGE?
If yes, it’s chemical
If no, it’s physical
Reactivity with Vinegar Gas bubbles are produced when vinegar is poured into baking soda
Change in texture Grinding baking soda into a fine, powdery substance is a physical change

45. Full sentences for full credit!
Writing Prompt #3 (of 3)
Write the answer on your green sheet.
Pick one of the demonstrations you saw and describe an indicator of a chemical change in that demonstration.
Full sentences for full credit!