CHEM120 Chapter Notes - Chapter 1: Chemical Element, Significant Figures, Distillation
Matter: Its Properties and Measurements
1-1 The Scientific Method
- Natural Laws: are concise statements. Often in mathematical form about natural phenomena.
- Hypothesis: is a tentative explanation of a natural law.
- Theory: is a model or way of looking at nature that can be used to explain natural laws and
make further predictions about natural phenomena.
- Scientific Method: is the combination of observation, experimentation and formulation of laws
hypotheses and theories.
1-2 Properties of Matter
- Matter: is anything that occupies space and displays the properties of mass and inertia. All the
objects that we see around us consist of matter, even gases since they have mass. Sunlight
however is not matter because it is a form of energy.
- Composition: refers to the parts or components of a sample of mater and their relative
- Properties: are those qualities or attributes that we can use to distinguish one sample of matter
Physical Properties and Physical Changes
- Physical Property: is one that a sample of matter displays without changing its composition.
- Physical Change: some of the physical properties of the sample may change, but its composition
remains unchanged. (Liquid water → ice, looks different but its chemical composition of oxygen
and hydrogen remains the same)
Chemical Properties and Chemical Changes
- Chemical Change: one or more kinds of matter converted to new kinds of matter with different
- Chemical Property: is the ability (or inability) of a sample of matter to undergo a change in
composition under stated conditions.
1-3 Classification of Matter
- Matter is made up of very tiny units called atoms.
- Each different type of atom is the building block of a different chemical element.
- All matter is made up of the 112 elements on the PT.
- Compounds: are substances comprising atoms of two or more elements joined together.
- Molecules: is the smallest entity having the same proportions of the constituent atoms as does
the compound as a whole.
- Substances: a group of elements or compounds.
- Homogenous Mixture (or solution): a substance that is uniform in composition and properties
throughout. The compounds and elements are relatively the same proportion.
- Heterogeneous Mixture (or solution): the components separate into distinct regions. Thus, the
composition and physical properties vary from one part of the mixture to another.
- Filtration: process of separating a solid from the liquid in which it is suspended
- Distillation: a pure liquid is condensed from the vapor given off by boiling a solution
1-4 Measurement of Matter: SI (Metric) Units
- SI: International System of Units
- Mass: describes the quantity of matter in an object.
- Weight: is the force of gravity on an object. It is directly proportional to mass as shown in the
following mathematical expressions. W = g x m
- An object has a fixed mass, which is independent of where or how the mass is measured. Its
weight on the other hand may vary because the acceleration due to gravity varies slightly form
one point on the earth to another.
Can it be
Can it be
Is it uniform
1-5 Density and Percent Composition
- Density: is the ratio of mass to volume
- Extensive Property: is dependent on the quantity of matter observed. Both mass and volume
are extensive properties.
- Intensive Property: is independent of the amount of matter observed. Intensive Properties can
be used to identify substances.
1-6 Uncertainties in Scientific Measurements
- Systematic Errors: errors in measuring instruments
- Random Errors: Limitations in an experimenter’s skills and abilities lead to results that are too
high or too low.
- Precision: the closeness of agreement when the same quantity is measured several times.
- Accuracy: refers to how close a measured value is to the accepted or actual value.
1-7 Significant Figures