BLE Model Paper 5

He should not reply or share the code, and should delete the message: it is phishing, a fake message that tricks people into giving away a code or password, so that someone else can get into their account.

A group of cells of the same kind (or of a few kinds) that work together to do a particular job, such as muscle tissue or nerve tissue.

It destroys the homes (habitat) of the fish, insects and plants of the river bed, and makes the banks collapse, so the river’s life and the plants along it are lost.

A concave mirror: held close to a tooth, it gives an enlarged, erect image of it.

A magnet found in nature, a rock that is a magnet by itself, for example lodestone (magnetite).

It has one valence electron, like lithium and sodium, so it goes in group 1; but it is a gas and a non-metal, without the metallic properties of the other group 1 elements.

Duralumin (aluminium with a little copper, manganese and magnesium), because it is light and yet nearly as strong as steel.

No. An alkali is a base that dissolves in water. Some bases, such as copper oxide and iron oxide, don’t dissolve in water, so they are bases but not alkalis. (Every alkali is a base, but not every base is an alkali.)

• i.It pushes people towards the answer “yes”, the answer the question seems to want. A better question is short, asks one thing and gives choices, for example: “How do you make your drinking water safe? a. boil it b. filter it c. use chlorine drops d. nothing”.
• ii.Analyzing the data: counting the answers (for example as percentages, in a table or a bar diagram), so that she can draw a conclusion.

• i.The common cold is caused by a virus (rhinovirus). Antibiotics kill bacteria; a virus is not a cell and has no metabolism of its own, so antibiotics do nothing to it.
• ii.Rhizobium bacteria living in the root nodules of beans and lentils take nitrogen from the air and turn it into compounds plants can use. These stay in the soil and make it more fertile for the next crop.

• i.The principle of cultural conservation and public participation: the people themselves take part in the work, so they feel it is theirs, look after it, and it lasts.
• ii.The environmental aspect: the trees and grass protect the slope, soil and water (conserving the environment), which also keeps the canal and the plant working for a long time.

Any two:

• i.Metal is a good conductor of heat, so it carries the heat of the flame quickly to the food. Wood and plastic are poor conductors (insulators), so the heat doesn’t reach the hand holding the handle.
• ii.Air is a very poor conductor of heat. Several layers trap more still air between them than one thick layer does, so the body’s heat escapes more slowly.

• i.The bulbs of a house are joined in parallel: each is on its own branch between the live and the neutral wire, so losing one path doesn’t stop the current in the others.
• ii.In series, the same current passes through all the bulbs one after another and they share the 230 V, so each gets only part of it and glows dimly.

• i.Ammonia. A moist red litmus paper held at the mouth of the tube turns blue (ammonia is a basic gas); it also has a sharp smell, like a dirty toilet.
• ii.A base and an ammonium salt give a salt, ammonia and water:

$$2\text{NH}_4\text{Cl} + \text{Ca(OH)}_2 \rightarrow \text{CaCl}_2 + 2\text{NH}_3 + 2\text{H}_2\text{O}$$

No, it couldn’t.

• a.The dinosaurs lived in the Mesozoic era and died out at its end, about 66 million years ago, after an asteroid hit the Earth (only the birds, a group of dinosaurs, survived).
• b.Humans came very late, in the Cenozoic era: our species, Homo sapiens, appeared only about 300,000 years ago. So more than 65 million years separate the last dinosaurs from the first humans.

• i.An internet service provider (ISP): a company that gives people, businesses and offices access to the internet. Any one in Nepal: Nepal Telecom, WorldLink, Vianet, Subisu.
• ii.Uniform Resource Locator.
• iii.A collection of related web pages kept together under one address (URL), holding the information of a person or an organization.
• iv.A website, such as moecdc.gov.np, holds its own pages about one person or organization; a search engine, such as Google, is a program that searches the internet and lists the pages of many websites that match the keywords typed.

• i.The grafted saplings. The scion is a twig of the best tree itself, so the part that bears fruit has the same genes as that tree and gives the same fruit (and it starts bearing in a few years, because the scion is already mature).
• ii.A seed is formed by sexual reproduction: the pollen that fertilized the flower may have come from another tree. So each seedling is a new mix of two parents and shows variation; its fruit may be quite different, even sour.
• iii.All the trees will be identical (copies, with the same genes). A new disease or pest that harms one of them can harm them all, and he could lose the whole orchard at once.
• iv.No. Sexual reproduction gives young that are each a little different (variation). When the environment changes, for example with a new disease or a drought, some of them are likely to survive, and new and better varieties can be found among them. (Even the stock of a grafted sapling is grown from a seed.)

i. Largest face = 0.2 m × 0.1 m = 0.02 m².
$$P = \frac{F}{A} = \frac{30\ \text{N}}{0.02\ \text{m}^2} = 1{,}500\ \text{Pa}$$
ii. Smallest face = 0.1 m × 0.05 m = 0.005 m².
$$P = \frac{30\ \text{N}}{0.005\ \text{m}^2} = 6{,}000\ \text{Pa}$$

• iii.6,000 ÷ 1,500 = 4 times. It sinks deepest standing on its end (smallest face), because the same weight acts on the smallest area.
• iv.The force is now 4 × 30 N = 120 N on the same 0.02 m²:

$$P = \frac{120\ \text{N}}{0.02\ \text{m}^2} = 6{,}000\ \text{Pa}$$
the same pressure as one brick standing on its end.

• i.P and R: both have 4 valence electrons, so they are in the same group (group 14). (P is carbon, R is silicon.)
• ii.Q (neon): its outer shell is full, with 8 electrons, so it is already stable and neither gains nor loses electrons.
• iii.R. It has 3 shells and P has only 2; going down a group, each element has one more shell, so its atom is bigger.
• iv.S (aluminium) has 3 valence electrons. Atoms with 1 to 3 electrons in their outer shell react by losing them, and elements that lose electrons are metals.