CSS General Science and Ability Physical Sciences Syllabus

What are the umbra and penumbra in an eclipse?

The umbra is the dark central part of a shadow where light is fully blocked (causing a total eclipse); the penumbra is the lighter outer region where light is only partially blocked (causing a partial eclipse).

Why is a lunar eclipse visible from a larger area than a solar eclipse?

The Earth's shadow is much larger than the Moon's, so a lunar eclipse is visible from the entire night side of Earth, whereas a solar eclipse is seen only along a narrow path of totality.

What are equinoxes and solstices?

Equinoxes (around 21 March and 23 September) are when day and night are equal worldwide; solstices (around 21 June and 22 December) are when one hemisphere has its longest day and the other its shortest.

What is weather, and how does it differ from climate?

Weather is the short-term, day-to-day state of the atmosphere at a place; climate is the average weather pattern of a region over a long period (typically 30+ years).

Name the principal weather variables (elements of weather).

Temperature, atmospheric pressure, humidity, precipitation, wind (speed and direction), cloud cover, and sunshine/solar radiation.

What is atmospheric pressure and what instrument measures it?

Atmospheric pressure is the force exerted by the weight of the air column above a point; it is measured by a barometer. Standard sea-level pressure is about 1013 hPa (millibars).

What is the difference between absolute humidity and relative humidity?

Absolute humidity is the actual mass of water vapour per unit volume of air; relative humidity is the ratio (as a percentage) of actual water vapour to the maximum the air can hold at that temperature.

What instrument measures wind speed, and what measures wind direction?

An anemometer measures wind speed; a wind vane (weather vane) indicates wind direction.

What is the difference between weather variation and climate?

Weather variation refers to short-term fluctuations in atmospheric conditions; climate is the long-term average and range of weather, defining a region's characteristic conditions.

What is climate change and name one major human cause.

Climate change is a long-term shift in temperature and weather patterns; a major human cause is the emission of greenhouse gases (e.g., carbon dioxide) from burning fossil fuels.

What is the greenhouse effect?

The greenhouse effect is the trapping of outgoing infrared radiation by atmospheric gases (CO2, water vapour, methane), which warms the Earth's surface and keeps it habitable; excess gases cause global warming.

Define a geological hazard and give two examples.

A geological hazard is a natural process originating from the Earth's geology that can cause harm; examples include earthquakes, volcanic eruptions, and landslides.

What causes earthquakes and what instrument records them?

Earthquakes are caused by the sudden release of energy from movement along faults in the Earth's crust (plate tectonics); they are recorded by a seismograph.

What is the difference between the Richter scale and the Mercalli scale?

The Richter scale measures the magnitude (energy released) of an earthquake instrumentally; the Modified Mercalli scale measures intensity based on observed effects and damage.

Define a hydro-meteorological hazard and give two examples.

A hydro-meteorological hazard is one of atmospheric, hydrological, or oceanographic origin; examples include floods, cyclones, droughts, and heatwaves.

What is a tropical cyclone and what are its regional names?

A tropical cyclone is an intense low-pressure rotating storm with strong winds and heavy rain forming over warm oceans; it is called a hurricane in the Atlantic, a typhoon in the NW Pacific, and a cyclone in the Indian Ocean.

What is the difference between a hazard and a disaster?

A hazard is a potentially damaging natural or human event; a disaster occurs when a hazard strikes a vulnerable community and causes serious loss of life, property, or livelihood that exceeds local coping capacity.

What are the four phases of the disaster management cycle?

Mitigation, preparedness, response, and recovery.

What is the basic relationship that defines disaster risk?

Disaster Risk = (Hazard x Vulnerability) / Capacity; risk rises with greater hazard and vulnerability and falls with greater coping capacity.

What is renewable energy and give four examples.

Renewable energy comes from sources that are naturally replenished and not depleted by use; examples include solar, wind, hydro (water), geothermal, and biomass energy.

What is non-renewable energy and give three examples.

Non-renewable energy comes from finite sources that cannot be replenished on a human timescale; examples include coal, petroleum (oil), natural gas, and nuclear (uranium) fuel.

How do fossil fuels form and why are they classed as non-renewable?

Fossil fuels (coal, oil, gas) form from the remains of plants and animals buried and compressed over millions of years; their formation is so slow that they are effectively non-renewable.

What is energy conservation and why is it important?

Energy conservation is reducing energy consumption by using less or using it more efficiently; it conserves finite resources, cuts costs, and reduces greenhouse-gas emissions and pollution.

What is sustainable energy use?

Sustainable energy use means meeting present energy needs without compromising the ability of future generations to meet theirs, typically by favouring renewable sources and high efficiency.

Describe the basic structure of an atom and the charges of its particles.

An atom has a central nucleus containing positively charged protons and neutral neutrons, surrounded by negatively charged electrons in shells/orbitals.

What is the difference between atomic number and mass number?

The atomic number is the number of protons in an atom's nucleus (defining the element); the mass number is the total number of protons plus neutrons.

What are isotopes?

Isotopes are atoms of the same element (same number of protons/atomic number) but with different numbers of neutrons, giving them different mass numbers.

Define ionic and covalent bonding.

Ionic bonding is the electrostatic attraction between oppositely charged ions formed by transfer of electrons (usually metal to non-metal); covalent bonding is the sharing of electron pairs between atoms (usually between non-metals).

What is the electromagnetic spectrum, arranged by increasing frequency?

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays (in order of increasing frequency/energy and decreasing wavelength).

State the relationship between the speed, frequency and wavelength of electromagnetic waves.

Speed = frequency x wavelength (c = f x lambda), where c is the speed of light in a vacuum, about 3 x 10^8 m/s; all EM waves travel at this speed in a vacuum.

Compare ceramics, plastics and semiconductors by their basic nature and one key property.

Ceramics are inorganic, non-metallic solids that are hard, brittle and heat/corrosion resistant; plastics are organic polymers that are light, mouldable and good insulators; semiconductors (e.g., silicon) have conductivity between conductors and insulators and are the basis of electronic devices.