SCH 4C
THE METHOD OF SCIENTISTS
Any method which is a combination of curiosity and imagination and which uses experimentation to
look for regularities in nature is an acceptable method to use to solve problems.
The traditional form of the SCIENTIFIC METHOD follows these steps:
1. Recognize a problem.
2. Make a hypothesis. A hypothesis is a prediction or educated guess as to the outcome of the
problem.
3. Plan and do an experiment to test the hypothesis. Observations of the experiment are made.
4. Make conclusions. A conclusion is also called an inference or an interpretation.
OBSERVATION vs. INTERPRETATION
An observation is not the same as an interpretation. An observation is something which you can
detect using your senses; it is something which you can see, hear, smell, feel, taste or measure. An
interpretation is a conclusion or an explanation of all of the observations; it is something you know or
think you know. Be careful not to make interpretations in the observation section of a laboratory report,
leave these for the conclusion!
QUESTIONS
1. Decide whether each of the following is an observation (O) or a interpretation (I).
a) When the candle burns, carbon dioxide is given off.
b) The candle is 10 cm long.
c) The candle has a diameter of 2.5 cm and is cylindrical.
d) The candle flame has three different colours.
e) The black smoke coming from the candle flame is carbon.
f) The length of the candle changes slowly as the candle burns.
g) The wick extends from the top of the candle to the bottom.
h) Carbon causes the yellow colour in the candle flame.
i) The candle flame has sharp sides and a ragged top.
j) In the candle flame, the wick is black except for the very tip, which glows red.
PROPERTIES OF MATTER
MATTER is any substance which has mass and volume. PROPERTIES are characteristics. A
knowledge of the properties will help to identify unknown substances and determine their uses. There
are two types of properties namely qualitative and quantitative. Qualitative properties are those which
are detected using our senses. In contrast, quantitative properties involve measurements of some kind.
Some QUALITIATIVE PROPERTIES include:
1. STATE: There are 3 states of matter namely solid, liquid and gas or vapour. A gas is a substance which
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is in the gaseous state at room temperature (ie. oxygen gas or carbon dioxide gas). In contrast, a
vapour is the gaseous state of a substance which is either a liquid or solid at room temperature
(ie. water vapour or iodine vapour). Each state has different characteristics with respect to shape
and volume. Solids have both definite shape and volume. Gases have indefinite shape and
volume. Liquids have an indefinite shape but a definite volume.
COLOUR: Use words such as blue, orange, green,... A substance may be a mixed colour such as a reddishyellow. A substance with no colour is colourless.
TASTE: There are only four namely sweet, sour, salty and bitter. Pure water is tasteless because it has no
taste. Do not taste unknown substances because they may be harmful.
ODOUR: There are a variety of adjectives to describe odours. Those which are pleasant include sweet,
aromatic and fragrant. In contrast odours may be unpleasant, nauseating, sharp, strong or
choking. Sometimes odours may be compared to something; hydrogen sulphide gas smells like
rotten eggs. Smell unknowns carefully; waft the fumes towards your nose.
CLARITY: The 3 degrees of clarity are clear (transparent), cloudy (translucent), and opaque.
LUSTRE: Use words like shiny, dull, metallic, greasy,...
TEXTURE: This describes the "feel" of a substance and useful adjectives include smooth, rough, fine,
coarse, gritty, silky,...
FORM: The most common terms are crystalline, powdery and amorphous (no specific form).
HARDNESS: Use words such as hard, soft, flexible, brittle, malleable (may be hammered into thin sheets)
and ductile (may be stretched into thin wires).
VISCOSITY: Liquids may be thin, thick, oily, runny, syrupy,...
Some QUANTITATIVE PROPERTIES include:
11. BOILING POINT
12. MELTING POINT or FREEZING POINT
13. DENSITY
14. SOLUBILITY
15. CONDUCTIVITY
Quantitative properties are better for identifying unknowns than qualitative properties. For example
there are many colourless liquids but only one which will boil at 100oC or has a density of 1.0 g/mL.