BLE Model Paper 9

No, it is a plant cell: it has a cell wall and a large vacuole. A root grows in the dark, so its cells have no chloroplasts; they have colorless leucoplasts, which store food.

Natural vegetative propagation by leaf: each notch of the leaf has a tiny bud, which grows its own roots and shoot.

About 760 mmHg: it holds up a column of mercury 760 mm tall. This is about 100,000 Pa (1.01 × 10⁵ Pa).

A porcelain cup. Porcelain is an insulator (a poor conductor of heat), so the heat of the tea passes through it slowly: the tea stays hot longer and the cup doesn’t burn the hand.

No. The intensity of sound is proportional to the square of the amplitude ($I \propto A^2$), so doubling the amplitude makes the intensity four times as much.

One unit is 1 kilowatt-hour (kWh): the electrical energy used by an appliance of 1,000 W (1 kW) working for 1 hour.

Each has 7 valence electrons, so it needs just one more electron to complete its octet, and it gains that electron very readily.

Because every acid gives hydrogen ions (H⁺) when it dissolves in water, and these hydrogen ions cause the sour taste, the color changes of indicators and the reactions of acids.

• i.cell → tissue → organ → organ system (and all the systems together make the organism).
• ii.Tissue: muscle tissue (which pushes the food along by peristalsis) or glandular tissue (which makes digestive juices). Organ: the stomach, the small intestine or the food pipe.

• i.Genetic diversity: the variety among individuals of the same species (here, breeds of goat), caused by differences in their genes.
• ii.Ecosystem diversity: the variety of ecosystems, land and water, with different physical conditions and living things, in one area.

• i.$$\text{MA} = \frac{L}{E} = \frac{700\ \text{N}}{200\ \text{N}} = 3.5, \qquad \text{VR} = \frac{\text{distance moved by effort}}{\text{distance moved by load}} = \frac{80\ \text{cm}}{20\ \text{cm}} = 4$$
• ii.$$\eta = \frac{\text{MA}}{\text{VR}} \times 100\% = \frac{3.5}{4} \times 100\% = 87.5\%$$

It is less than 100% because of friction at the fulcrum: part of the input work is turned into heat.

• i.Heat travels along the rod by conduction: the particles near the flame vibrate harder and pass the extra vibration on to their neighbors, one after another. So the wax nearest the flame melts first, then the next, and so on.
• ii.From the copper rod, because copper has a much higher thermal conductivity than iron (about 400 against 80), so it carries heat along faster.

• i.A convex mirror. It always forms an erect, diminished image and shows a wide view, so drivers can see the vehicles coming round the bend.
• ii.A concave mirror. As a converging mirror, it gathers the Sun’s rays to its focus, where the pot is kept.

• i.The N-pole of a compass needle points north. Unlike poles attract, so the magnetic pole that pulls it there must be a south pole.
• ii.The Earth is a huge magnet. Standing for years in the north–south direction in the Earth’s magnetic field, the iron slowly becomes magnetized.

• i.The solution that turns blue litmus red is ammonium chloride (acidic); the one that turns red litmus blue is washing soda (basic); the one that changes neither is table salt (neutral).
• ii.Ammonium chloride is formed from a strong acid (hydrochloric acid) and a weak base (ammonium hydroxide), so it is an acidic salt.

• i.After the dinosaurs died out, at the start of the Cenozoic, mammals, including human beings, spread into every habitat and evolved into the many kinds we know (elephants, horses, whales, primates).
• ii.Cryptozoic means “hidden life”. Life in that eon was tiny and soft-bodied and left few clear fossils, so it stayed hidden for a long time.

• i.A: making a hypothesis; B: preparing the materials; C: analyzing the data.
• ii.For example: “Drinking water stays cooler in an earthen pot than in a steel pot.”
• iii.Different: only the material of the pot (earth or steel). Kept the same (any two): the size of the pots, the amount of water, the water’s starting temperature (the same tap), the place where the pots are kept, the times of filling and measuring, the same thermometer.
• iv.On every day, the water in the earthen pot was 6 to 8 °C cooler than in the steel pot, so an earthen pot keeps drinking water cooler than a steel pot, and her hypothesis is supported.

• i.Xerography. It is called dry because no ink or liquid is used: the copy is made with light, electric charge, a powder (toner), heat and pressure.
• ii.A bright lamp lights the page, and the light reflected from its white parts falls on the drum through a lens. Wherever light falls, the charge leaks away; the dark letters reflect almost no light, so the drum stays charged only in the shapes of the letters.
• iii.The toner, a fine black powder, is given the opposite charge. Opposite charges attract, so it sticks only to the charged letter shapes on the drum.
• iv.A sheet of paper from the tray, given a stronger charge than the drum, runs under the drum and pulls the toner off it onto itself.

• i.A: pollination; B: fertilization.
• ii.One male gamete fuses with the egg cell to form the zygote, which grows into the embryo; the other fuses with the two polar nuclei to form the endosperm nucleus, which grows into the endosperm. Two fusions in each ovule: double fertilization.
• iii.Insects, such as honey bees; insect pollination is called entomophily.
• iv.20. Each seed comes from one fertilized ovule, and each ovule is fertilized by the male gametes of its own pollen tube, which grows from one pollen grain.

• i.X: 2, 8, 8, 1 (the outermost shell holds no more than 8, so the 19th electron starts the N shell). Y: 2, 6.
• ii.X: valency 1, since it has 1 valence electron, which it loses. Y: valency 2, since it has 6 valence electrons and gains 2 to make 8 (8 − 6 = 2).
• iii.X is potassium (K) and Y is oxygen (O). Crossing over the valencies, K’s 1 goes to O and O’s 2 goes to K: K₂O₁, written K₂O (potassium oxide).
• iv.Molecular weight of K₂O = 2 × 39 + 16 = 78 + 16 = 94.