Introduction To Chemistry

Introduction
What is chemistry?
• The science that systematically studies the
composition, structure, and properties of matter, as
well as the changes it undergoes.
.
• Chemistry can be seen in all aspects of
life e.g. development of pharmaceuticals,
leaf color changes in growth of plants,
etc.
Why Study Chemistry?

We study chemistry because:
• it has a considerable impact on society
(health care, food, clothing, conservation
of natural resources, environmental issues
etc.).
• it is part of your curriculum! Chemistry
serves biology, engineering, agriculture,
geology, physics, nutrition and dietetics,
pharmacy etc… Chemistry is the central
science
• Studying Chemistry can help you develop
positive, aggressive attitude toward problem
solving and can help boost your confidence
The Scientific Method
• Is a systematic approach to solving
problems.
• Involves asking specific questions and
seeking ways to resolve the problem.
• Consists of the following steps:
Steps in the Scientific method
1. Make observations
• First you recognize the problem and state it
clearly
2. Construct a hypothesis
• A hypothesis is a tentative or possible
explanation for what has been observed.
3.Experimental design and data collection
• Test your hypothesis by carrying out
experiments. This will test whether your
hypothesis is true or false.
Example:
Step 1: Make observation
• Ask questions – what are the effect of Windhoek
Lager on males compared to females?
Step 2: Formulate hypotheses
• Windhoek larger affects both male and females the
same way
• Windhoek larger makes males more talkative and
have no effect on females.
Step 3: Perform experiment
• Would you consider the age and weight of subjects
in an alcohol study?
• Would you test with one can of beer or 6 packs of
beer?
• Steps involved in a scientific method
Types of data
• There are two types of data that can be
collected during an experiment: qualitative
and quantitative data.
Types of data
• Qualitative data relates to general
description of an observation. They are
descriptive in nature. E.g. females talked
more after 3 glasses of beer, while men
were unable to focus.
• Quantitative data relates to numbers or
quantity from a measurement. They are
numerical in nature. E.g. 10.0 mL of
ethanol produced 7.89 g, 7.85 g and
7.92 g of ethanol from 3 repeated
measurements.
Identify the qualitative and quantitative data from the
observation below
Theories and laws
• Theory: Many independent experimental
confirmation of a hypothesis through
experiments may result in a theory. The
theory explains a pattern in data. E.g.
Dalton’s atomic theory.
• Law : A statement (often mathematical)

showing a relationship between phenomena
that is true under the same
conditions.(concise statement or equation that
summarises tested hypotheses). E.g the law
of gravity, the law of conservation of mass.
Matter
Matter: Anything that has mass and occupies
space.
Atoms are the smallest building units of
matter.
States of matter
There are three states of matter: solid, liquid
and gas.
Solid state:molecules arranged closely and
orderly with little room for movement.
– Defined shape and volume.
Liquid state:
• Molecules are close but not restricted and
can move fairly freely.
• Has defined volume but no defined
shape, take the shape of container.
Gas state:
• Molecules are further apart and they
move freely.
• No defined shape or volume.
• The three states of matter can be inter-converted via
processes such as melting, evaporation, condensation,
freezing, sublimation and deposition.
sublimation deposition
• SOLID ==========> GAS ==========> SOLID
melting freezing/solidification
• SOLID =======> LIQUID ==========> SOLID
Condensation vaporization
GAS ============> LIQUID ===========> GAS
Classification of matter
Classes of matter
Main classes of matter are: pure substances
and mixtures.
Pure substance- refers to matter that has a

constant composition and unique/ distinct
properties.
Two types of pure substances are

elements and compounds.
• Elements- pure substances that cannot be
separated into simpler stable substances.
An element is composed of only one kind
of atom. E.g H2 O2, C, N2, Cu, Fe, etc.
O2 H2 N2
• Compounds- substances that consist of
two or more atoms of different elements
chemically combined in fixed proportions,
e.g. CO2, NaCℓ, H2O, etc.
CO2 NaCℓ H2O

Mixtures
• A mixture is a combination of two or more
substances in which each substance retains its
own chemical identity and can be separated
from each other by physical means.
Two types of mixtures:

1. Homogeneous mixture: has the same uniform
appearance throughout. Also referred to as
solutions, e.g. vanilla ice-cream; the air around
you is a homogenous mixture of gases; solid
solutions also exist: brass is a homogenous
mixture of the metals copper and zinc
2. Heterogeneous mixture: components are not
uniformly mixed. It consists of visibly different
substances or phases, e.g. muesli, salad dressing
mixture.
Methods for separating Mixtures:

The processes used to separate a mixture are physical
processes that are based on differences in the physical
properties of the substances.
• Distillation
• Filtration: Used to separate a solid from a liquid
• Chromatography
• Crystallization
• Sublimation
Summary Classification of matter
Properties of Matter
• A property is a set of characteristics and
behaviors which describes a substance.
• Physical properties: Can be measured or
observed without changing the composition of
a substance.
• E.g Density, colour, odor, volume, state,
hardness, melting point, boiling point etc.
• Specific example: Recognizing a friend due to

unique characteristics or properties e.g thin
and tall, brown eyes etc
• Physical change: A change which alters
the a substance without changing its
composition. No new substances are
formed.
• Physical change might be caused by
grinding, cutting, crushing, bending,
breaking, heating/cooling (change in
phase), squishing.
• Chemical property:- observed or
measured after a chemical change
(chemical reactions) in composition of a
substance
• there is a permanent re-arrangement of
components. e.g. Flammability,
corrosiveness, reactivity with acid, etc.
• Properties of matter can also be broadly
classified as intensive or extensive
properties.
Extensive property: Depends on the amount
or quantity of matter present.
• It is cumulative, meaning it increases with
addition of material i.e 10 g potatoes +
10 g potatoes = 20 g potatoes , hence
mass is an extensive property.
-
• 20 L petrol + 20 L petrol = 40 L petrol;
hence volume is an extensive property.
Other examples are length, weight, etc.
Intensive property: Is independent of the

amount or quantity of matter present.
• Hence intensive properties are not
cumulative or additive.
• For example 20 L of water and 100 L of
water at the same temperature and pressure
has the same density, therefore density is an
intensive property.
• Other examples are color, odor, temperature,
electrical conductivity, texture, etc.
Exercises
1. Are the following intensive or extensive properties?
a) Colour e) length
b) Temperature f) density
c) Mass g) melting point
d) Volume
2. Indicate whether the following statements

describe a physical or a chemical change.
a) crushing a can b) breaking a bottle,
c) gasoline ignited, d)Jewelry tarnishes,
e) boiling an egg.
3. Are the following physical or chemical
properties?:
a) Colour,
b) flammability,
c) corrosion,
d) density,
e) smell.
4. State whether the following pictures represent a
compound, mixture, or element.
a) Rocks b) Jelly beans
c) sand d) Bronze medal

e) sugar f) diamond
g) Tea h) Salt

Introduction To Chemistry

Uploaded by

Copyright:

Available Formats

Introduction To Chemistry

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Introduction To Chemistry

Uploaded by

Copyright:

Available Formats

Introduction

Why Study Chemistry?

• Law : A statement (often mathematical)

Pure substance- refers to matter that has a

Two types of pure substances are

CO2 NaCℓ H2O

Two types of mixtures:

Methods for separating Mixtures:

• Specific example: Recognizing a friend due to

Intensive property: Is independent of the

2. Indicate whether the following statements

a) Rocks b) Jelly beans

c) sand d) Bronze medal

You might also like