Unit B: Matter and Chemical Change (Nature of Science emphasis)
Overview: Different materials have different
properties. The ability to distinguish between different substances and make sense of their properties,
interactions and changes requires development of ideas about chemical substance. In this unit, students are introduced to the formal study
of chemical substances through laboratory investigations and introductory studies of chemical theory. In the laboratory, students observe and compare chemical substances and, with guidance on safety, investigate the properties of materials and the ways they interact.
In conjunction with these studies, students are introduced to ideas about elements and compounds, and corresponding structural ideas of atoms and molecules. Theoretical ideas are introduced as means for explaining,
interpreting and extending their laboratory findings; and include a general introduction to the periodic table, chemical nomenclature and simplified ways of representing chemical reactions.
This unit builds on ideas introduced in Grade 8, Unit B: Mix and Flow
ofMatter, and introduces ideas that will be developed further in Science 10, Unit A: Energy and Matter in Chemical
Change.
illustrate and explain how our observations
are guided by our initial ideas and by the tools and techniques that we use (e.g., describe how ideas such as "solubility" and "conductivity" can be used to guide observations; describe how the tools or techniques of study can affect what
we observe) investigate
and describe properties of materials (e.g., investigate and describe the melting-point, solubility and conductivity of materials observed) describe and
apply different ways of classifying materials based on their composition and
properties - distinguish between pure substances, solutions and mixtures
- distinguish between metals and nonmetals
- identify and apply other methods of classification
identify conditions under which properties
of a material are changed, and critically evaluate if a new substance has been produced
Students will: Describe and interpret patterns in chemical reactions.
Identify evidence for conservation of chemical
substance (e.g., identify and apply techniques for containing and comparing the quantity of reactants and products
in a chemical reaction).
Identify
conditions that affectrates of reactions (e.g., investigate and describe how factors, such as heat, concentration, surface area and electrical energy, can
affect a chemical reaction)
Students will Describe ideas used in interpreting the chemical nature of matter, both in
the past and present, and identify example evidence that has contributed to the development of these ideas.
Distinguish between observation and theory
Provide examples
of how models and theoretical ideas are used in predicting and explaining observations (e.g. note that kinetic
molecular theory is used to explain why materials contract when cooled, but that other theoretical ideas are needed
to explain why water expands as it cools from 4 to 0 Celsius)
Describe early
ideas about the nature of substances and chemical change (e.g. describe early ideas about the nature of gases and
their role in combustion and respiration)
Describe, illustrate
and interpret early ideas about the nature of particles that underlie matter (e.g. describe and compare Dalton's
billiard ball model of the atom, and Rutherford's planetary model)
Demonstrate
an understanding of the periodic table, focusing on the first 18 elements, and use
the periodic table to identify the number of protons and electrons in each atom.
Sub Atomic Particles:
There are 3 types of sub-atomic particles.
Protons - relatively large, have a positive charge.
Neutrons - approx. same mass as proton, no charge.
Electrons - small ( ~ 1/2000 mass of proton), negative charge.
Nucleus:
Contains protons and neutrons
Makes up most of the mass of an atom.
Small part of atoms volume.
Atomic Number
The number of protons in the atom.
The number of electrons = the number of protons, hence the overall charge in an atom is 0.
Mass Number
The number of protons in the nucleus + the number of neutrons in the nucleus, i.e. the total
number of particles in the nucleus.
Element
Consists of atoms all having the same atomic numbers.
There are 92 naturally occurring elements.
The Periodic Table:
The Periodic Table of Elements is how chemists
organize all the Elements. The elements in any one column are said to be a family of elements. These are closely related element
because they behave similarly in chemical reactions.
Isotopes
Atoms which have the same atomic number but different mass numbers.
i.e., belong to the same element but have different number of neutrons.
e.g. 126C + 146C
--> top number = mass number
--> bottom number = atomic number
The Atomic Theory:
All matter is made up of tiny particles. (Difference between elements and compounds) The Atomic
Theory states that
All matter is made up of tiny particles called atoms
Atoms of one element are the same. When other atoms combine with other atoms they create
molecules.
No ordinary means can destroy atoms or create atoms.
* Molecules contain identical atoms, Compounds contain atoms of at least two different elements.*
* Information relating to the above material can be reached @ the following
sites; *
Chemical Formulas: Chemical Symbol is an abbreviation for compounds and elements either a capital letter
or a capital letter followed by a lower case letter. Single symbols represent elements and combination symbols
represent compounds. Chemical Formulas: The combination of symbols represents a particular compound. This indicates
which elements are in a compound and in what proportion they represent.
Identify examples of combining ratios found
in some common materials (Students should recognize that some materials have multiple combining ratios (e.g. CO,
CO2, Fe203, Fe304) [Prerequisite Skill: Grade 8 Mathematics,
Number Operations, SO 151
Assemble or draw simple molecular models
(e.g., construct models
of some carbon compounds using toothpicks, peas and cubes of potatoes)
Describe
familiar chemical reactions, and represent these reactions using word equations and chemical formulas.
Chemical Reactions- Changes, Chemical Change and Mass
Changes:
There are two types of change. They include:
Physical change and chemical change. Physical changes are changes in which there is no new matter produced. ( e.g..
water can change state; freezing ,melting, boiling etc.) A chemical change or reaction is in which one or more
new substances are formed. ( from properties different from those of the substances you started with) Examples
include frying an egg, and metal rusting. There are certain clues to help you identify what change a substance
has undergone. They are shown below.
Clues for a chemical change:
-The substance has changed in colour.
-Heat or light is given off during the reaction.
-Bubbles or has has formed.
-Solid of a precipitate has formed.
-The change is very difficult to reverse.
Chemical Reactions: Chemical changes are referred to as a chemical reaction. Any substance used up in the
reaction is called a reactant. Any substance that is produced in a chemical reaction is a product. A complex description
of a chemical reaction would include a detailed description of what happens, but the short way to describe it is
to say what is used and what is produced. A word equation gives the names of all the reactants ( separated by a
+ ) followed by a ------> pointing to a product . e.g.
Iron + Oxygen ----> Rust
----------------- -------
.........Reactants Product
[* Iron and oxygen produces Rust*]
Mass and Chemical Change:
Matter changes, but does the amount of matter also change? The earliest chemists ,who were called
"natural scientists" did many experiments to answer questions. They were limited in 2 ways. First instruments
did not allow them to make accurate measurements. Second until the atomic theory of matter was developed in 1808,
they couldn't explain all their observations.
