Haryana BSEH Secondary Science flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Neutralisation reaction

A reaction between an acid and a base that produces a salt and water, releasing heat. Example: hydrochloric acid plus sodium hydroxide gives sodium chloride and water.

Reactivity series

A list of metals ordered by how readily they lose electrons and react. More reactive metals displace less reactive ones from salt solutions; copper and silver do not react with dilute acids.

pH scale

A 0 to 14 scale measuring hydrogen ion concentration. Values below 7 are acidic, 7 is neutral and above 7 is basic; each unit represents a tenfold change.

Ionic versus covalent bond

Ionic bonding transfers electrons from metal to non-metal, giving charged ions that conduct when molten. Covalent bonding shares electron pairs between non-metals, forming molecules.

Mitochondria

Membrane-bound cell organelles where aerobic respiration occurs. They release energy stored in glucose as usable chemical energy, so cells with high energy demand contain many of them.

Xylem and phloem

Two transport tissues in plants. Xylem carries water and minerals upward from roots and is dead tissue; phloem carries food in both directions and is living tissue.

Photosynthesis equation

Six carbon dioxide molecules plus six water molecules, using chlorophyll and sunlight, produce one glucose molecule and six oxygen molecules; light energy becomes chemical energy.

Dominant and recessive alleles

Alternative forms of a gene. A dominant allele expresses its trait even when only one copy is present; a recessive allele shows its trait only when two copies are present.

Laws of reflection

The angle of incidence equals the angle of reflection, and the incident ray, reflected ray and normal lie in one plane. These laws hold for all reflecting surfaces.

Concave versus convex mirror

A concave mirror converges light and can form real or virtual images. A convex mirror diverges light and always gives a virtual, erect, diminished image, useful as a rear-view mirror.

Refractive index

The ratio of the speed of light in vacuum to its speed in a medium. It determines how much light bends when entering a denser or rarer medium.

Lens power

The reciprocal of focal length measured in metres, expressed in dioptres. A short focal length gives high power; converging lenses have positive power.

Ohm's law

At constant temperature, the current through a conductor is directly proportional to the potential difference across it. The constant of proportionality is the resistance, V equals I times R.

Series circuit

A circuit in which components are connected end to end so the same current flows through each. Total resistance is the sum, and voltage divides across components.

Electric power

The rate at which electrical energy is converted, equal to voltage times current, or current squared times resistance. Its unit is the watt.

Fleming's left-hand rule

A rule giving the direction of force on a current-carrying conductor in a magnetic field: forefinger field, middle finger current, thumb motion. It underlies the electric motor.

Greenhouse effect

Warming of the Earth when certain atmospheric gases trap outgoing infrared radiation. It keeps the planet habitable, but increased gas concentrations enhance warming.

Ozone layer depletion

Thinning of stratospheric ozone mainly by chlorofluorocarbons, allowing more ultraviolet radiation to reach the surface. The Montreal Protocol phases out such substances.

Biodegradable waste

Waste that microorganisms can break down into simpler harmless substances, such as vegetable peels, paper and cotton. Non-biodegradable waste like plastic persists for decades.

Acid rain

Rain made acidic by sulphur dioxide and nitrogen oxides from burning fossil fuels. It corrodes buildings, acidifies lakes and damages crops and soil.

Meniscus reading

The curved surface of a liquid in a narrow tube. Read the lowest point at eye level to avoid parallax error when measuring volume.

Testing for carbon dioxide

Pass the gas through freshly prepared limewater. Carbon dioxide turns it milky or cloudy because insoluble calcium carbonate particles form.

Ammeter and voltmeter

An ammeter measures current and is connected in series with the component. A voltmeter measures potential difference and is connected in parallel across it.

Controlled variable

A factor kept constant throughout an experiment so that any change in the result can be attributed only to the independent variable being tested.

Accuracy versus precision

Accuracy is how close a measurement is to the true value; precision is how close repeated measurements are to each other. A measurement can be precise yet inaccurate.

Hypothesis

A testable, falsifiable prediction about the relationship between variables, stated before the experiment and checked against collected evidence.

SI base units

The seven fundamental units: metre, kilogram, second, ampere, kelvin, mole and candela. All other units, such as the newton and joule, are derived from them.

Balanced diet

Food supplying all required nutrients in correct proportions: carbohydrates and fats for energy, proteins for growth and repair, vitamins and minerals for regulation, plus water and roughage.

Scurvy and rickets

Deficiency diseases: scurvy results from lack of vitamin C, causing bleeding gums and weakness; rickets results from lack of vitamin D, causing soft, deformed bones.

Kwashiorkor and marasmus

Protein-energy malnutrition forms. Kwashiorkor is protein deficiency with swelling and oedema; marasmus is severe deficiency of both protein and energy, with extreme wasting.

Vaccination

Introducing weakened or killed pathogens or their antigens so the immune system makes antibodies and memory cells, giving protection against future infection by that pathogen.

Oral rehydration solution

A mixture of water, salt and glucose given to replace fluid and electrolytes lost through diarrhoea, preventing dehydration. It should be given in small frequent sips.