Grade 8 General Science:

Length

The distance between two points.

Hand-span

Distance from the tip of the little finger to the thumb when the hand is stretched out.

Digit

Width of an adult male fingertip.

Cubit

Distance from the elbow tip to the middle fingertip with an extended arm.

Foot

Distance from the heel to the big toe.

Pace

Distance from the heel of one foot to the heel of the same foot after a normal walking step.

Arm span (Fathom)

Distance between the middle fingertips of both outstretched arms.

Mass

The amount of matter in an object.

Weqet

Unit for measuring gold powder.

Quntal

A bag representing 100 kilograms of grains.

Feresula

Unit for measuring pepper and coffee, equal to 17 kg.

Time

The duration of an interval.

Shadow of a tree

Method for estimating time by observing changes in shadow length throughout the day.

Volume

The space occupied by an object.

Jog

A plastic cup used for measuring liquids.

Tassa

A can used for measuring cereals, pulses, liquids, and solids.

Sini

A small ceramic cup used for coffee, pulses, and spices.

Birchiko

A glass used for measuring pulses and liquids.

Kubaya

A mug used for measuring cereals, pulses, and liquids.

Fundamental Physical Quantities

Measurable properties that cannot be expressed in terms of other quantities.

Fundamental quantities

Length, mass, time, temperature, electric current, luminous intensity, and amount of substance.

Meter (m)

The SI unit for measuring length.

Kilogram (kg)

The SI unit for measuring mass.

Second (s)

The SI unit for measuring time.

Kelvin (K)

The SI unit for measuring temperature.

Derived quantities

Quantities expressed in terms of fundamental quantities.

Area (A)

Derived quantity calculated as length times width.

Volume (V)

Derived quantity calculated in cubic units.

Speed (v)

Derived quantity calculated as distance over time.

Density (ρ)

Derived quantity expressed in kilograms per cubic meter (kg/m³).

Prefix

A symbol representing very large or very small numbers.

Mega (M)

Represents 1,000,000.

Kilo (k)

Represents 1,000.

Centi (c)

Represents 0.01.

Milli (m)

Represents 0.001.

Micro (μ)

Represents 0.000001.

Accuracy

How close a measurement is to its known value.

Precision

How close multiple measurements are to each other.

Scientific Method

The process by which scientists approach their work.

Hypothesis

A tentative explanation based on gathered data.

Mass balance

Instruments used to compare the mass of an object to a known mass.

Chemical Equation

A representation of a chemical reaction using symbols.

Salts

Compounds consisting of the positive ion of a base and the negative ion of an acid.

Neutralization Reaction

The reaction of acids with bases to form salt and water.

Oxides

Binary compounds containing oxygen and another element.

Acids

Substances that release hydrogen ions (H⁺) in aqueous solution.

Bases

Substances that neutralize acids.

Indicators

Dyes extracted from plants that change color in the presence of an acid or a base.

Hydrocarbon

A compound containing only carbon and hydrogen.

Alkanes

Saturated hydrocarbons with only single bonds.

Alkenes

Unsaturated hydrocarbons with at least one double bond.

Alkynes

Unsaturated hydrocarbons with at least one triple bond.

Atomic Number (Z)

The number of protons in an atom's nucleus.

Mass Number (A)

The total number of protons and neutrons in an atom's nucleus.

Molecule

A group of atoms bonded together, can be of the same or different elements.

Proton

Positively charged subatomic particle found in the nucleus of an atom.

Neutron

Neutral subatomic particle found in the nucleus of an atom.

Electron

Negatively charged subatomic particle found outside the nucleus of an atom.

Anion

A negatively charged ion.

Cation

A positively charged ion.

Essential Medicine

Medicine required to meet the priority health care needs of the population.

Physical changes

Changes affecting one or more physical properties of a substance.

Chemical changes

Changes that result in the formation of new chemical substances.

Vaporization

The process of turning from liquid into vapor.

Condensation

The process of turning from vapor into liquid.

Sublimation

The process of turning from solid directly to gas.

Deposition

The process of turning from gas directly to solid.

Freezing

The process of turning from liquid into solid.

Melting

The process of turning from solid into liquid.

Radioactive decay

The process by which an unstable atomic nucleus loses energy by radiation.

Half-life

The time required for half of the radioactive atoms in a sample to decay.

Solvent

The substance in which solute is dissolved to form a solution.

Solute

The substance dissolved in a solution.

Solution

A homogeneous mixture of two or more substances.

Concentration

The amount of solute in a given volume of solution.

Electrical charge

A property of matter that causes it to experience a force when placed in an electromagnetic field.

Ionic bond

A chemical bond formed between two ions with opposite charges.

Covalent bond

A chemical bond formed by the sharing of electron pairs between atoms.

Metallic bond

A bond formed between metal atoms, where electrons are shared and free-moving.

Noble gases

Inert gases found in Group 18 of the periodic table.

Acids vs Bases

Acids release H⁺ ions, while bases release OH⁻ ions in solution.

Hydrochloric Acid

Strong acid used for various industrial processes.

Sulfuric Acid

A strong acid used in batteries and drain cleaners.

Acetic Acid

Weak acid found in vinegar.

Test tube

A cylindrical glass or plastic tube used in laboratories.

Volatile liquids

Liquids that readily vaporize at low temperatures.

Diethyl ether

A highly flammable solvent used in laboratories.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed.

Photosynthesis

The process by which green plants convert light energy into chemical energy.

Photosystem II

A protein and chlorophyll complex involved in the light-dependent reactions of photosynthesis.

Calvin cycle

Series of biochemical redox reactions that take place in the chloroplasts.

Nucleic acids

Biomolecules essential for all known forms of life, DNA and RNA.

Chromatin

The complex of DNA and proteins found in eukaryotic cells.

Gene expression

The process by which information from a gene is used to synthesize functional gene products.

Mutation

A change in the DNA sequence of an organism.

Transcription

The process of copying a segment of DNA into RNA.

Translation

The process of synthesizing proteins from RNA.

Cell cycle

The series of events that take place in a cell leading to its division and duplication.

Mitosis

A type of cell division resulting in two genetically identical daughter cells.

Meiosis

A type of cell division that reduces the chromosome number by half, resulting in four gametes.