BLE Model Paper 10

The first page you see when you open a website. It sets the look of the whole site and has links to its other pages.

The speaker (with its socket for earphones): many ATMs speak their instructions aloud, so a person who can't see the screen can follow them.

A worm: it spreads by itself across networks. A virus spreads only when the files it hides in are copied or opened, and nobody opened any.

It climbs over and smothers the trees and plants, spreads fast with no natural enemies here, and pushes out the native plants (and with them the animals that feed on them), so the biodiversity of the forest falls.

The resting state of a ripe seed, in which it stays alive but unchanged and doesn't grow, for months or years if kept dry.

The 9 W LED bulb: it gives the same light while using far less electrical energy. A filament bulb turns more than 90% of its energy into heat, not light, so it costs more to run.

Halogen means “salt maker”: these very reactive non-metals join with metals to make salts; for example, chlorine and sodium make common salt (sodium chloride).

The rest of the mass has not been lost: the burning made gases (carbon dioxide, water vapor and smoke) that escaped into the air. If the wood were burnt in a sealed vessel, as Lavoisier did with his reactions, the total mass would stay the same.

• i.$\dfrac{18}{40} \times 100 = 45\%$ (sacks 35%, bamboo bins 20%).
• ii.a. 45% is less than half of the households, so even in her tole “most” is wrong; she can only say that airtight drums are the most common of the three ways.
• b.She asked only 40 households of one tole. They can't stand for all the families of Nepal, where the climate, the crops and the ways of storing grain differ from place to place.

Any two:

• a.Brand development: many people in and around Dharan learn about the shop, its menu and its offers, as the page works as an advertisement.
• b.Customer interaction: customers can write reviews and comments; good reviews bring in new customers, and bad ones show the owner what to improve.
• c.The shop can tell its customers at once about new dishes, opening hours or home delivery.

• i.The spiny babbler is found only in Nepal (it is Nepal's only endemic bird, living in the scrub of the middle hills). There is no population anywhere else to take its place, so losing it here would mean its extinction.
• ii.About three out of four kinds of food crops depend, at least in part, on animals, mostly bees and other insects, to pollinate them. Without bees, fewer flowers are pollinated, and fewer fruits and seeds form.

• i.In a dry seed almost no chemical activity (metabolism) goes on, so it stays dormant, doesn't germinate or use up its stored food, and keeps alive for a long time. (Dry seeds also don't let molds and bacteria grow on them.)
• ii.In a bean the hypocotyl grows into a hook and pulls the cotyledons above the soil (epigeal germination). There they turn green and make food by photosynthesis for a few days, the young plant's first leaves, until its true leaves grow.

• i.The loudspeaker is 90 − 60 = 30 dB louder. Each 10 dB more means ten times the intensity, so 30 dB more means 10 × 10 × 10 = 1,000 times the intensity.
• ii.No. 10 dB less means one tenth of the intensity, not half. (It does sound about half as loud, since each 10 dB sounds about twice as loud to us; that may be why he thinks so.)

• i.The Sun sends out fast, electrically charged particles (the solar wind). The Earth's magnetic field turns most of them aside and steers the rest towards the polar regions, where they make the upper air glow as the aurora.
• ii.When molten lava cools into igneous rock, its magnetic minerals freeze in the direction of the Earth's field at that time. The field has flipped many times, so the direction of a rock's magnetism tells geologists when it formed.

i. Skeleton: H₂ + O₂ → H₂O. There are 2 O on the left and 1 on the right, so put 2 before H₂O: H₂ + O₂ → 2H₂O (now 4 H on the right). Put 2 before H₂:
$$2\text{H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O}$$
Check: left 4 H, 2 O; right 4 H, 2 O.
ii. Left: 1 Ca, 1 C, 3 O. Right: 1 Ca, 1 C, and 1 + 2 = 3 O. Each kind of atom is equal on both sides, so it is balanced.

Any two:

• a.Coal: burnt for the very high heat of cement factories, brick kilns and blast furnaces.
• b.Petroleum: runs vehicles, and is used to cook and to make electricity.
• c.Natural gas: burnt for heat and to make electricity (it feeds the flames of Jwala Mai at Muktinath).
• d.Uranium: fuels nuclear power stations.

• i.Mitochondria release energy from food (glucose) by cellular respiration. The porter's leg muscles work hard all day and need a great deal of energy, so their cells have many mitochondria.
• ii.Lysosomes are full of digestive enzymes. A white blood cell swallows germs and digests them, so it needs many lysosomes.
• iii.The Golgi body sorts, packs and sends out (secretes) the substances a cell makes. A gland cell secretes saliva with its enzymes all the time, so its Golgi bodies are large.
• iv.Ribosomes join amino acids to make proteins, so a cell making much protein needs many of them, and the nucleolus makes the ribosomes, so it is large too.

• i.$$P = h\,d\,g = 3.4 \times 1000 \times 9.8 = 33{,}320\ \text{Pa}$$
• ii.From $P = \dfrac{F}{A}$,

$$F = P \times A = 33{,}320\ \text{Pa} \times 0.05\ \text{m}^2 = 1{,}666\ \text{N}$$
iii. From $P = h\,d\,g$,
$$h = \frac{P}{d\,g} = \frac{33{,}320}{13{,}600 \times 9.8} = \frac{33{,}320}{133{,}280} = 0.25\ \text{m} = 25\ \text{cm}$$
(Mercury is 13.6 times as dense as water, so 3.4 m ÷ 13.6 = 0.25 m.)
iv. It stays the same. The pressure of a liquid depends only on its depth, its density and g ($P = hdg$), not on the width or area of the container.

• i.By radiation. Between the Sun and the Earth's air is almost empty space, with no particles to pass heat on by conduction or to carry it by convection; radiation needs no material medium.
• ii.Sunlight (short waves) passes easily through the glass and warms the black plate, but the long-wave infrared that the warm plate gives out can hardly get back through the glass, and the glass also stops the warm air from blowing away. So heat is trapped, as in a greenhouse, and the water gets hotter.
• iii.The water heated in the panel expands, becomes less dense and rises up the pipe into the tank, while the cooler, denser water from the bottom of the tank sinks down the other pipe into the lower end of the panel. This natural convection current keeps going as long as the Sun shines, and it works only if the tank is above the panel.
• iv.The insulation is a poor conductor, so little heat escapes from the hot water by conduction, and the shiny cover is a poor emitter, so little heat is lost by radiation. The water stays hot into the night.

• i.A salt is the compound formed when the hydrogen of an acid is replaced by a metal (or by ammonium), as in the reaction between an acid and a base (acid + base → salt + water).
• ii.Neutral salts, from a strong acid and a strong base: sodium chloride (NaCl). Acidic salts, from a strong acid and a weak base: ammonium chloride (NH₄Cl) or copper sulphate. Basic salts, from a strong base and a weak acid: sodium carbonate (Na₂CO₃, washing soda).
• iii.Any two: most salts dissolve in water; most are white or colorless, though some are colored (copper sulphate blue); most don't taste salty (and many are poisonous); they have high melting and boiling points; neutral salts don't change the color of indicators.
• iv.Washing soda: for washing and cleaning, to remove the permanent hardness of water, or to make glass, paper and soap. Baking soda: to make baking powder, to make antacids, or in some fire extinguishers.