Welcome Oct' 56, 2006

1
Welcome! Oct. 5-6, 2006

• Please pick up the new lab and any graded papers.
• You will need your homework 1-8 for todays
  warm-up.
• Hmwk
• On-Line Textbook Read Ch. 2 Section 3

2
Agenda

• Warm-Up Homework Discussion
• Notes Physical Changes
• Activity From Ice to Steam
• Notes Chemical Changes
• Activity Unknown Powders - Mystery

3
Question 1

• State the relationship between atoms and
  elements. Are both atoms and elements matter?
• An atom is the smallest unit of an element that
  has that elements properties.
• Both atoms and elements are matter.

4
Question 2

• List the two types of pure substances.
• Elements are made of all of the same atoms
• Compounds are made of all of the same molecules.

5
Question 3

• Describe matter, and explain why light is not
  matter. Is light made of atoms and elements?
• Matter has mass and occupies space. Light has
  neither mass nor volume, nor is it made up of
  atoms.

6
Question 4

• Define molecule, and give examples of a molecule
  formed by one element and a molecule formed by
  two elements.
• A molecule is the smallest unit of a substance
  that keeps all of the physical and chemical
  properties of that substance.
• O2 or H2O

7
Question 5

• Classify each of the following as an element or a
  compound.
• a. Sulfur, S2 c. Carbon monoxide, CO
• b. Methane CH4 d. Cobalt, Co
• Element
• Compound
• Compound
• Element

8
Question 6

• State the chemical formula of water.
• H2O

9
Question 7

• Compare and Contrast mixtures and pure
  substances. Give an example of each.
• A pure substance has the same composition
  throughout and definite properties. Salt
• A mixture, such as air, contains more than one
  pure substance. Air (N, O)

10
Question 8

• David says, Pure honey means it has nothing
  else added. Susan says, The honey is not
  really pure. It is a mixture of many
  substances. Who is right? Explain your answer.
• Davids statement reflects the common meaning of
  pure.
• Susans use of the word pure is more
  scientifically correct because honey is a mixture
  of several different compounds.

11
Changes of Matter

• Water changes to steam to produce electricity.
• Liquid gasoline changes to a gas to power car
  engines.

12
Physical Changes

• Physical change affects one or more physical
  properties of a substance without changing its
  identity.
• You can break a piece of chalk in two this
  changes its physical properties of size and shape
  but it is still chalk.
• Hair cut
• Dissolving sugar
• Melting ice
• Sanding wood
• Crushing an aluminum can

13
Physical changes dont change a substances
identity

• Quartz and sand are both made up of SiO2, but
  they look different.
• When quartz is crushed sand is produced. This
  is a physical change.

14
Dissolving is a physical change

• When sugar dissolves in water it seems to
  disappear but it is still there. When you
  drink the water it is sweet.

15
Mixtures can be physically separated.

• How do you separate sand from salt?
• How could you separate iron filings from
  cornflakes?
• How would you separate the mushrooms from a
  mushroom, pepperoni, and black olive pizza?

16
From Ice to Steam
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Welcome! Oct. 9-10, 2006

• Please take out your temperature vs. time table,
  graph, and conclusion questions. We will discuss
  these today.
• Today we will be looking at chemical changes and
  the phases of matter.
• Hmwk
• Read Chapter 3 section 1 Complete Review
  Questions 1-8

18
Chemical Change

• Chemical Change occurs when one or more
  substances are changed into entirely new
  substances with different properties
• Battery dies the chemicals have changed
• Oxygen breathed in changed into carbon dioxide
  and water
• Fruit ripening
• Digesting your food
• Sour milk

19
Chemical changes form new substances that have
different properties

• When you bake a cake the eggs and flour that
  you use have different properties than the cake
  that you produce.

20
Chemical changes can be detected

• When food burns
• When paint fades.
• When eggs cook..

21
Chemical Changes

• Most chemical changes cannot be reversed.
• You can not unbake a cake

22
Compounds can be broken down.

• A electric current passed through melted table
  salt can separate the elements sodium and
  chlorine.

23
Unknown powders - mystery