Assam ASSEB HSLC General Science flashcards
Assam ASSEB HSLC General Science · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Sublimation
- Direct change of a solid into vapour on heating without passing through the liquid state, and the reverse on cooling. Camphor, naphthalene, iodine and dry ice show it.
- Mixture versus compound
- A mixture has components in any ratio and can be separated physically, while a compound has elements chemically combined in a fixed ratio and can be broken only chemically.
- Fractional distillation
- A separation method for two or more miscible liquids with different boiling points, using a fractionating column. It separates petroleum fractions and the components of liquid air.
- Valency
- The combining capacity of an element, equal to the number of electrons it loses, gains or shares to complete its outermost shell. Group 2 elements have valency 2.
- Ionic bond
- A chemical bond formed when one atom transfers electrons to another, creating oppositely charged ions held by electrostatic attraction, as in sodium chloride.
- Covalent bond
- A bond formed by the sharing of one or more pairs of electrons between two atoms, usually non-metals, as in water, methane and oxygen gas.
- Balanced chemical equation
- An equation in which the number of atoms of each element is equal on both sides, obeying the law of conservation of mass. State symbols and conditions are often added.
- Neutralisation reaction
- A reaction between an acid and a base producing salt and water, releasing heat. For example, hydrochloric acid with sodium hydroxide gives sodium chloride and water.
- pH scale
- A scale from 0 to 14 measuring hydrogen ion concentration: below 7 acidic, 7 neutral, above 7 basic. Each unit change means a tenfold change in H+ concentration.
- Plaster of Paris
- Calcium sulphate hemihydrate, made by heating gypsum to about 373 K. Mixed with water it sets hard and is used for casts and moulds.
- Reactivity series
- Metals arranged in decreasing order of chemical reactivity: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, hydrogen, copper, mercury, silver, gold.
- Galvanisation
- Coating iron or steel with a thin layer of zinc to prevent rusting. Zinc corrodes first, protecting the iron beneath by sacrificial protection.
- Roasting and calcination
- Roasting heats a sulphide ore strongly in air to give an oxide; calcination heats a carbonate ore without air to drive off carbon dioxide.
- Functional group
- An atom or group of atoms attached to a carbon chain that determines the compound's characteristic properties, such as hydroxyl, carboxyl, aldehyde or ketone groups.
- Micelle
- A spherical cluster of soap molecules in water, with hydrophobic tails pointing inward around oil droplets and hydrophilic heads outward, allowing grease to be washed away.
- Incomplete combustion
- Burning a fuel in insufficient oxygen, producing carbon monoxide and soot instead of carbon dioxide and water. Carbon monoxide is poisonous because it binds haemoglobin.
- Mitochondrion
- A double-membraned cell organelle where aerobic respiration occurs, releasing energy as ATP. It is called the powerhouse of the cell.
- Meristematic tissue
- A plant tissue of actively dividing cells found at root and shoot tips, in the cambium and at leaf bases, responsible for growth in length and girth.
- Mitosis versus meiosis
- Mitosis produces two identical diploid cells for growth and repair; meiosis produces four haploid cells with genetic variation, forming gametes in sexual reproduction.
- Xylem and phloem
- Xylem carries water and dissolved minerals upward from roots, driven by transpiration pull. Phloem translocates food made in leaves to other plant parts in both directions.
- Aerobic respiration
- The breakdown of glucose in the presence of oxygen inside mitochondria, producing carbon dioxide, water and a large amount of energy stored as ATP.
- Reflex action
- A fast, automatic response to a stimulus, such as withdrawing a hand from a hot object, completed through a reflex arc involving the spinal cord.
- Insulin
- A hormone secreted by the pancreas that lowers blood glucose by promoting its uptake and storage as glycogen. Deficiency causes diabetes mellitus.
- Dominant and recessive alleles
- A dominant allele expresses its trait even when present with a different allele; a recessive allele shows its trait only when both alleles are recessive.
- Acquired immunity
- Specific protection gained after exposure to a pathogen or through vaccination, involving the production of antibodies and memory cells by the immune system.
- Ten percent law
- Only about ten percent of the energy at one trophic level is transferred to the next; the rest is lost as heat and in life processes, limiting food chains to four or five links.
- Newton's second law
- The rate of change of momentum of a body is proportional to the applied force and takes place in the direction of the force, giving F = ma.
- Conservation of momentum
- In the absence of an external force, the total momentum of a system remains constant. This explains recoil of a gun and collisions.
- Archimedes' principle
- The upthrust on a body immersed in a fluid equals the weight of fluid displaced by it. A body floats if its density is less than the fluid's.
- Power
- The rate of doing work or transferring energy, measured in watts, where one watt equals one joule per second. Power equals work divided by time.
- Ohm's law
- At constant temperature, the current through a conductor is directly proportional to the potential difference across it, giving V = IR where R is resistance in ohms.
- Joule's law of heating
- The heat produced in a resistor equals I squared times R times t, so heating rises with the square of the current, with resistance and with time.