Certificate of Secondary Education (CSE) Science Syllabus

State the law of reflection of light.

The angle of incidence equals the angle of reflection ($i = r$), both measured from the normal (the line perpendicular to the surface).

What is refraction of light?

Refraction is the change in direction (bending) of light as it passes between media of different optical density, caused by a change in its speed. Light bends towards the normal entering a denser medium and away from it leaving.

How do sound waves and the speed of sound compare in solids, liquids and gases?

Sound is a longitudinal wave needing a medium. It travels fastest in solids, slower in liquids and slowest in gases, because particles are closer together in solids. It cannot travel through a vacuum.

What do the frequency and amplitude of a sound wave determine?

Frequency (in hertz, Hz) determines the pitch — higher frequency means higher pitch. Amplitude determines the loudness/volume — larger amplitude means louder sound.

Describe the arrangement and movement of particles in solids, liquids and gases.

Solid: particles closely packed in a fixed regular pattern, vibrating in place. Liquid: particles close together but irregular, able to move/slide past each other. Gas: particles far apart, moving quickly in all directions.

Name the changes of state between solid, liquid and gas.

Melting (solid$\to$liquid), freezing (liquid$\to$solid), evaporating/boiling (liquid$\to$gas), condensing (gas$\to$liquid), and sublimation (solid$\to$gas directly).

What is the equation for density?

$\rho = \frac{m}{V}$, where $\rho$ is density, $m$ is mass and $V$ is volume. A common unit is $\text{g/cm}^{3}$ or $\text{kg/m}^{3}$.

What is the difference between an element, a compound and a mixture?

An element contains only one type of atom. A compound contains two or more different elements chemically bonded in fixed proportions. A mixture contains different substances not chemically bonded, which can be separated physically.

How do you separate a mixture of (a) sand and water and (b) salt and water?

(a) Sand and water: filtration (sand is the insoluble residue, water passes through). (b) Salt and water: evaporation or distillation (water evaporates, leaving salt; distillation recovers the water).

What is the difference between a physical change and a chemical change?

A physical change (e.g. melting, dissolving) is usually reversible and forms no new substance. A chemical change (e.g. burning, rusting) forms one or more new substances and is usually not easily reversible.

Write the word and balanced symbol equation for the combustion of methane.

Methane $+$ oxygen $\to$ carbon dioxide $+$ water. Symbol equation: $\ce{CH4 + 2O2 -> CO2 + 2H2O}$.

What is the law of conservation of mass in a chemical reaction?

Mass is conserved: the total mass of the products equals the total mass of the reactants, because atoms are only rearranged, not created or destroyed.

What is the general word equation for an acid reacting with a metal?

Acid $+$ metal $\to$ salt $+$ hydrogen. For example: $\ce{2HCl + Mg -> MgCl2 + H2}$.

What colour does universal indicator show in acids, neutral solutions and alkalis, and the pH ranges?

Acids: red/orange/yellow, $\text{pH} < 7$. Neutral: green, $\text{pH} = 7$. Alkalis: blue/purple, $\text{pH} > 7$.

Give two examples of useful materials and a property that makes each suitable for its use.

Examples: copper for electrical wires (good conductor of electricity, ductile); plastic for insulation (electrical insulator, flexible); steel for bridges (strong, hard). Any property matched correctly to a use is acceptable.

What conditions are needed for iron to rust, and what is rust?

Iron rusts when both water and oxygen (air) are present. Rust is hydrated iron(III) oxide. Rusting can be prevented by coating (paint, oil) or galvanising (zinc coating).

List four key structures found in an animal cell.

Nucleus (controls the cell, holds DNA), cytoplasm (where reactions occur), cell membrane (controls what enters/leaves) and mitochondria (site of respiration).

Which three extra structures does a plant cell have that an animal cell does not?

A cell wall (made of cellulose, for support), chloroplasts (contain chlorophyll for photosynthesis) and a large permanent vacuole (filled with cell sap).

Name the seven life processes of living organisms (MRS GREN).

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Write the word equation for aerobic respiration.

Glucose $+$ oxygen $\to$ carbon dioxide $+$ water ($+$ energy released). Symbol: $\ce{C6H12O6 + 6O2 -> 6CO2 + 6H2O}$.

Name the main organs of the human digestive system in order.

Mouth $\to$ oesophagus $\to$ stomach $\to$ small intestine $\to$ large intestine $\to$ rectum $\to$ anus (with the liver and pancreas producing digestive juices/enzymes).

What are the roles of the heart, arteries, veins and capillaries in circulation?

The heart pumps blood. Arteries carry blood away from the heart (high pressure). Veins return blood to the heart (have valves). Capillaries are tiny vessels where exchange of substances with cells occurs.

Write the word equation for photosynthesis and state where it occurs.

Carbon dioxide $+$ water $\xrightarrow{\text{light}}$ glucose $+$ oxygen. It occurs in the chloroplasts of plant cells, using light energy absorbed by chlorophyll. Symbol: $\ce{6CO2 + 6H2O -> C6H12O6 + 6O2}$.

State the functions of a plant's roots, stem and leaves.

Roots anchor the plant and absorb water and mineral ions. The stem supports the plant and transports water and food. Leaves are the main site of photosynthesis and gas exchange.

What is pollination and how does it differ from fertilisation in plants?

Pollination is the transfer of pollen from the anther (male) to the stigma (female). Fertilisation is when the pollen nucleus fuses with the egg cell (ovule) to form a seed. Pollination comes before fertilisation.

Name the main stages of the human life cycle / growth.

Fertilisation $\to$ embryo/foetus (development in the uterus) $\to$ birth (baby) $\to$ childhood $\to$ puberty/adolescence $\to$ adulthood $\to$ old age.

What is an adaptation? Give an example.

An adaptation is a feature that helps an organism survive and reproduce in its habitat. Example: a camel has a hump storing fat and wide feet for walking on sand, helping it survive in the desert.

What is a habitat and what is meant by a population and a community?

A habitat is the place where an organism lives. A population is all the members of one species in a habitat. A community is all the populations of different species living in the same habitat.

In a food chain, what do the arrows represent and what are producers and consumers?

The arrows show the direction of energy (and biomass) flow, from the eaten to the eater. A producer (usually a green plant) makes its own food by photosynthesis. Consumers eat other organisms (herbivores, carnivores, omnivores).

What is the difference between a food chain and a food web?

A food chain shows a single linear feeding sequence. A food web is several interconnected food chains, showing the many feeding relationships in a habitat.

Name two causes of air pollution and one environmental effect of each.

Carbon dioxide from burning fossil fuels causes global warming (greenhouse effect). Sulfur dioxide from burning fossil fuels causes acid rain, which damages plants and waterways.

What is conservation and name two ways to conserve resources/the environment.

Conservation is protecting and managing the environment and its resources. Methods include recycling materials, reducing waste, replanting trees (reforestation) and protecting habitats/endangered species (e.g. nature reserves).

What is a fair test (controlled experiment) when planning an investigation?

A fair test changes only one variable (the independent variable), measures the effect (the dependent variable), and keeps all other variables (control variables) the same, so the results are valid.

Define the independent, dependent and control variables.

Independent variable: the one you deliberately change. Dependent variable: the one you measure. Control variables: the ones you keep constant to make the test fair.

Why should an experiment be repeated, and what is an anomalous result?

Repeating an experiment and taking a mean (average) improves reliability and reduces the effect of random error. An anomalous result is a value that does not fit the pattern; it is usually ignored when calculating the mean.

What is the difference between accuracy and precision in measurements?

Accuracy is how close a measurement is to the true value. Precision is how close repeated measurements are to each other (consistency). Results can be precise but not accurate.

How do you calculate the mean (average) of a set of repeated readings?

$\text{mean} = \frac{\text{sum of values}}{\text{number of values}}$. For example, the mean of $4$, $5$ and $6$ is $\frac{4+5+6}{3} = 5$.

When drawing a conclusion, what should a valid conclusion be based on?

A valid conclusion should describe the pattern or relationship shown by the data (the evidence), state whether it supports the prediction/hypothesis, and only make claims the results actually support.

What is the difference between a continuous and a discontinuous (categoric) variable, and which graph suits each?

A continuous variable can take any numerical value (e.g. temperature, length) and is plotted as a line graph. A discontinuous/categoric variable falls into categories (e.g. colour, type) and is shown on a bar chart.