SEC 1 SCIENCE
Light
Refraction
The bending of light as it passes from one transparent medium into another of a different optical density.
When a light ray is refracted, it bends toward the normal.
Reflection
angle of incidence: the angle between a incident ray on a surface and the line perpendicular to the normal.
Mirrors
5 properties of an image formed by a plane mirror
Upright
Virtual
Laterally inverted
Same size as the object
Same distance away from the mirror as the object is away from the mirror.
Concave
Convex
curving inward, image is magnified
curving outward, image is smaller than object.
Dispersion of light
The separating of white light into its component colours
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(Red, Orange, Yellow, Green, Blue, Indigo, Violet)
Violet bends the most.
Radiation
Use of infrared radiation
Thermal imaging in airports
Use of ultraviolet radiation
Sterilisation of medical equipments, sun tanning
Cells
Microscopes
objective lens
fine adjustment knob
Eyepiece
stage
coarse adjustment knob
coarse adjustment knob
Cell structure
Nucleus: Responsible for cell reproduction
Controls cell activities
Contains chromosomes
Usually the largest structure in an animal cell
Vacuole: Stores water and other nutrients needed for the organism to survive
Usually small, numerous and temporary in an animal cell
Cytoplasm: Serves as the site where many chemical reactions take place
Cell membrane: Partially permeable
Controls the substances entering or leaving the cell
Mitochondrion : Site of aerobic respiration where glucose is oxidized to release energy
Cellulose cell wall: fully permeable
Supports the cell and gives it a regular shape
Chloroplasts: Site of photosynthesis
Level of organization in the human body: cells, tissues, organs, organ systems
Division of labour: The breakdown of work into small and specific tasks for maximum efficiency
States of Matter
Particulate nature of matter
Liquid
All matter is made up of particles which are in constant and random motion
Solid
Gas
Packed closely
Orderly arrangement
Vibrate about their fixed positions
Very strong forces between particles
Fixed shape and volume
cannot be compressed
Packed closely
disorderly arrangement
Slide past one another
Strong forces between particles
no fixed shape
Fixed volume
cannot be compressed
Far apart
disorderly arrangement
Move freely at high speeds
Weak forces between particles
no fixed shape or volume
can be compressed
Does the temperature change during
Melting: NO
Boiling: NO
freezing: NO
condensation: NO
Atoms
charge of a neutron: 0
charge of a electron; -1
charge of a proton: +1
Separation techniques
Period table
Angle of reflection: The angle between the reflected ray and the normal
Period: horizontal row
Group: Vertical column
Elements are pure substances that cannot be broken down into two or more simpler substances.
Compounds and mixtures
Compounds: pure substances that are made up of two or more elements chemically combined in a fixed proportion by mass
Mixtures: Substances that is made of two or more substances not chemically combined
A molecule is made of 2 or more atoms that are chemically combined
Solute: A substance that is dissolved in a solution
Solvent: A liquid substance capable of dissolving other substances
Solution: A mixture that forms when one substance dissolves another
Techniques
filtration: To separate insoluble substances from a suspension
Evaporation: To obtain soluble solids from a solution
Distillation: To obtain the liquid from a solution
paper chromatography: To separate substances with different solubilities
The start line in paper chromatography must be drawn in pencil and not ink as pencil lead is insoluble in water.
NEWater
Microfiltration, Reverse osmosis, Ultraviolet disinfection
reverse osmosis: water is forced through a semipermeable membrane at high pressure
Definition of solubility: the amount of solute that can dissolve in a given amount of solvent at a given temperature