BGCSE Science Double Award Paper 3 (October/November 2015) Review

Vocabulary-style practice flashcards covering physics, chemistry, and biology concepts from the 2015 Botswana General Certificate of Secondary Education Science Double Award Paper 3.

Terminal velocity

The constant speed reached by an object falling through air when air resistance increases to match the weight of the object.

Air resistance

The force acting against a falling object that increases as the object descends from the start to terminal velocity.

Transformer B

A step-down transformer used to reduce voltage from $230\,kV$ to $25\,kV$ before electricity enters houses.

Potential energy decrease

The energy lost by water falling from a dam, calculated using the formula $m \times g \times h$; for $500\,kg$ falling $15\,m$, it is $75000\,J$.

Maximum possible velocity

The theoretical speed of falling water calculated by assuming all potential energy is converted to kinetic energy ($\Delta E_p = \frac{1}{2} m v^2$).

Soft iron core

A component of an electromagnet used because it is easily magnetized and demagnetized to switch a high voltage circuit on and off.

Insulator (Plastic)

The material used for the handle of an electric iron to prevent the transfer of heat and electricity to the user.

Earth wire

A safety wire connected to the metal sole of an iron to protect users from electric shock in case of a fault.

Input power

The rate of energy transfer, calculated as energy divided by time (e.g., $3\,kWh / 2\,hours = 1.5\,kW$).

Cost of electricity

The total financial charge for energy use, calculated by multiplying energy in $kWh$ by the rate (e.g., $3\,kWh \times P0.65/kWh = P1.95$).

Conduction

The process by which heat energy passes through a metal boiler to heat the water inside.

Convection

The process by which heat energy is transferred through the water from a boiler to a storage tank via the movement of the fluid itself.

Background radiation

The low-level radiation detected (e.g., $10\text{ counts/second}$) when no radioactive source is present in a lead shield.

Gamma radiation

The type of radiation from a source that can penetrate both paper and aluminum sheets, maintaining a count rate of $40\text{ counts/second}$ in the experiment.

Carbon monoxide

A toxic gas produced from the incomplete combustion of fuels.

Bromine

A substance used to distinguish between alkanes and alkenes.

Allotropes

The term used to describe different physical forms of the same element, such as diamond and graphite for carbon.

Relative molecular mass ($M_r$)

The sum of the relative atomic masses of the atoms in a molecular formula; for sodium carbonate ($Na_2CO_3$), this value is $106$.

Molar volume of a gas

The volume occupied by one mole of any gas at room temperature and pressure ($r.t.p.$), which is $24\,dm^3$.

Bio-petrol

An ester compound made from vegetable oil and methanol.

Empirical formula

The simplest whole-number ratio of atoms of each element in a compound; for glycerol ($C_3H_8O_3$), it remains $C_3H_8O_3$ if it cannot be further simplified.

Hypoglycaemia

A condition characterized by low blood sugar, which can occur in diabetic people if they are injected with too much insulin or exercise excessively.

Insulin

A hormone secreted by the pancreas that regulates blood sugar levels; it must be injected because it would be digested if taken orally.

Wilting

The loss of turgidity in plants leading to drooping, caused when plants lose water faster than they can absorb it, such as when excess fertilizer is added to the soil.

Diffusion

The process by which fumes or smells from a substance (like fertilizer) travel through the air to reach a person.

Animal Cell

A type of cell (identified as cell P in the text) that lacks a cell wall and chloroplasts.

Food chain

A sequence showing the flow of energy between trophic levels, such as: mophane trees $\rightarrow$ mophane worms $\rightarrow$ people.