BLE Model Paper 2

Food and drink can pick up chemicals from the bench or from our hands, and we would then swallow them.

An online journal or information website on which a writer, or a group of writers, posts their thoughts, experiences or knowledge on a subject, with the newest post at the top.

A set-top box for internet TV (IPTV), which receives and decodes the signal and shows the channels on the TV.

Different varieties have different genes (genetic diversity), so some of them might resist the disease and survive; the whole harvest wouldn’t be lost.

In the same direction, $v_{AB} = v_A - v_B = 20\ \text{m/s} - 14\ \text{m/s} = 6\ \text{m/s}$, forward.

Each of them has one valence electron (valency 1), so they have similar properties, and they are placed together in group 1.

The same element, chlorine. What makes an element what it is is the number of protons (its atomic number), which is 17 in both; a different number of neutrons changes only the atomic weight (35 and 37).

The Milky Way.

i. $$\text{percentage} = \frac{28}{80} \times 100 = 35\%$$
(LPG: 44 ÷ 80 × 100 = 55%; electric: 8 ÷ 80 × 100 = 10%; together 100%.)
ii. Any one conclusion supported by the data, for example: more than half the households (55%) cook with LPG; about a third (35%) still cook with firewood; only one household in ten (10%) cooks with electricity.

• i.Wi-Fi uses radio waves sent out by the router. Walls, water and metal on the way weaken them, so a few rooms away little of the signal is left.
• ii.A chatbot puts together answers that sound right from patterns in what it has read. It sometimes states false things confidently, even inventing facts and sources, so important facts must be checked in a textbook, with a teacher or on an official website.

• i.Within about 200 km from south to north, Nepal’s land rises from about 59 m to 8,849 m above sea level. So it has every climate from tropical to arctic-like, with many ecosystems (118 types), monsoon rain and varied soils, and each has its own plants and animals.
• ii.Water hyacinth is an invasive plant with no natural enemies here, so it spreads fast and covers the water. It blocks the light and air from the water below, so the plants there can’t make food and the fish run short of oxygen.

• i.$$P = h\,d\,g = 5 \times 1000 \times 9.8 = 49{,}000\ \text{Pa}$$
• ii.The pressure of water increases with depth. The higher the tank, the farther the taps are below the water level, so the water comes out of them with a greater pressure.

• i.The transparent plastic lets the Sun’s short-wave radiation (light) into the tunnel, where the soil and plants absorb it and warm up. The warm soil and plants give out long-wave heat radiation, which the plastic lets out only in part, and the plastic also stops the warm air from blowing away. So heat is trapped inside.
• ii.No. The natural greenhouse effect keeps the Earth’s average temperature at about 15 °C. Without it, the Earth would be about −18 °C and frozen, and life would hardly be possible. Only a greenhouse effect made too strong by extra greenhouse gases is harmful, causing global warming.

i. Heater: $P$ = 1,200 W = 1.2 kW, $t$ = 30 min = 0.5 h: E.C. = 1.2 × 1 × 0.5 = 0.6 kWh a day.
Bulbs: $P$ = 10 W = 0.01 kW, $N$ = 5, $t$ = 6 h: E.C. = 0.01 × 5 × 6 = 0.3 kWh a day.
In a day: 0.6 + 0.3 = 0.9 kWh; in 30 days: 0.9 × 30 = 27 units.
ii. Bill = units × rate = 27 × Rs 9 = Rs 243.

• i.A chemical change: a new substance, magnesium oxide, is formed, and it can’t simply be turned back into magnesium.
• ii.Magnesium + oxygen → magnesium oxide

$$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$$
(Check: 2 Mg and 2 O on each side.)

A group of stars that seems to make a particular pattern in the sky (such as a hunter or a ladle), with the region of the sky around it, is called a constellation. The sky is divided into 88 constellations.
Uses (any one): they tell the time of night and the season; they show directions (the Saptarishi’s pointer stars lead to the Pole Star, which shows north).

i. A plant cell, as on the left of the figure, labelled: cell wall, cell membrane, cytoplasm, nucleus (pushed to one side), chloroplasts, mitochondria and the large central vacuole.

• ii.Any two: the cell wall, chloroplasts, one large central vacuole.
• iii.A plant cell has chloroplasts, whose chlorophyll carries out photosynthesis: in sunlight they make carbohydrates from carbon dioxide and water. An animal cell has no chloroplasts, so it must get its food ready-made.
• iv.A plant cell has a tough, rigid cell wall. When water flows in, the vacuole swells and presses against the wall, which hardly stretches, so the cell only becomes firm. An animal cell has only a thin, elastic cell membrane, which can burst if too much water gets in.

i. A flower cut in half, labelled: pedicel, receptacle, sepal, petal, stamen (anther and filament), and pistil (stigma, style and ovary with ovules).

• ii.Male: the androecium, the stamens, each an anther on a filament (the anther makes the pollen grains). Female: the gynoecium, the pistil, with the stigma, style and ovary (the ovary holds the ovules).
• iii.The transfer of pollen grains from an anther to a stigma of the same kind of plant is called pollination.
• iv.The ovary becomes the fruit, and the ovules become the seeds.

• i.$$T = \frac{1}{f} = \frac{1}{400\ \text{Hz}} = 0.0025\ \text{s}$$
• ii.From $v = f\lambda$,

$$\lambda = \frac{v}{f} = \frac{340\ \text{m/s}}{400\ \text{Hz}} = 0.85\ \text{m}$$

• iii.$$I = \frac{P}{A} = \frac{0.05\ \text{W}}{10\ \text{m}^2} = 0.005\ \text{W/m}^2 \;(5 \times 10^{-3}\ \text{W/m}^2)$$
• iv.Power is the sound energy passing each second, so in $t$ = 2 min = 120 s,

$$\text{energy} = P \times t = 0.05\ \text{W} \times 120\ \text{s} = 6\ \text{J}$$

• i.K is an acid (it turns blue litmus red and methyl orange red). L is a base (it turns red litmus blue and phenolphthalein pink). M is neutral (it changes neither litmus, and phenolphthalein stays colorless).
• ii.Methyl orange is yellow in a base and also in a neutral liquid, so it can show an acid but can’t tell a base from a neutral liquid. Red litmus or phenolphthalein is needed for that.
• iii.Hydrochloric acid + sodium hydroxide → sodium chloride + water

$$\text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}$$
iv. Neutral. Sodium chloride is formed from a strong acid (hydrochloric acid) and a strong base (sodium hydroxide).