BLE Model Paper 6

Observation is the process of experiencing an object, an event or a process very carefully with our sense organs (and, where they aren’t enough, with instruments such as a microscope).

Hacking is getting into a computer, website or network without permission, to steal, change or destroy data, or to shut it down.

Backing up his data regularly onto another drive or the cloud: the photos could then be restored on a new phone.

A suitable temperature (warmth). Both sets had water and air, but it was too cold in the refrigerator for the enzymes in the seeds to work.

Rest and motion depend on the reference point. She takes the bus (herself) as the reference point, and compared with the bus the trees keep changing their position, falling behind it. Compared with the ground, the trees are at rest.

So that if a fault ever makes the body live, the current flows straight down the earth wire into the ground, the fuse blows or the MCB trips, and the person holding the iron is not shocked.

Helium’s only shell is the K shell, which can hold just 2 electrons, so it is already full and stable. Helium neither gains nor loses electrons and hardly reacts, like the other inert gases, so it belongs with them in group 18. Magnesium’s 2 outer electrons are in a shell that isn’t full, and it loses them easily.

By the criss-cross method, Ca₁Cl₂: CaCl₂.

• i.Red litmus can show only a base (it turns blue), and blue litmus can show only an acid (it turns red). With one strip alone, an acid or a base may leave it unchanged and look neutral; a liquid is neutral only when neither strip changes.
• ii.So that others know exactly what was done (the objective, materials, method and results) and can check it or repeat it.

No, it isn’t safe.

• a.The password is easy to guess: anyone who knows him, or looks at his social media, knows his name and birth year. A strong password is long and hard to guess.
• b.He uses the same password for every account: if a hacker or a phishing message gets it once, the thief can open all three, including the wallet with his money. Each account should have its own strong password (with two-factor authentication turned on).

• i.The radicle grows into the root system, and the plumule into the shoot system (the stem and leaves).
• ii.Food (starch and protein), for the young plant to use until it can make its own food by photosynthesis.

• i.Second-class lever, because the load (the bricks) is between the fulcrum (the axle of the wheel) and the effort (her hands).
• ii.Load distance = 0.4 m, effort distance = 1.2 m. By the principle of the lever,

$$E \times \text{E.D.} = L \times \text{L.D.} \quad\Rightarrow\quad E = \frac{600 \times 0.4}{1.2} = 200\ \text{N}$$

• i.The whistle gives out ultrasound, above 20 kHz. A human ear hears only up to about 20 kHz, but a dog can hear ultrasound.
• ii.Ultrasound has a very short wavelength, so it goes in a narrow beam and echoes back even from small parts and boundaries inside the body; the picture is built from these echoes, without cutting the body and without harmful rays.

• i.Brown (live) to the right-hand pin, blue (neutral) to the left-hand pin, and green-and-yellow (earth) to the top pin, the biggest one.
• ii.So that a tug on the cable pulls on the cord grip, not on the three screws: the wires don’t come loose and touch each other or the case.

i. Put 2 before CaO (2 O on each side), then 2 before Ca (2 Ca on each side):
$$2\text{Ca} + \text{O}_2 \rightarrow 2\text{CaO}$$
ii. Put 2 before HCl (2 H and 2 Cl on each side):
$$\text{H}_2 + \text{Cl}_2 \rightarrow 2\text{HCl}$$

• i.Much of the world’s coal formed from the swamp forests of tree ferns and giant club mosses of the late Paleozoic era (the Carboniferous period). Those plants stored the energy of sunlight in their bodies by photosynthesis, and burning the coal gives out that stored energy.
• ii.The first air was made of gases from volcanoes (water vapor, carbon dioxide, nitrogen, ammonia, methane), with almost no free oxygen. Later, tiny living things in the sea began photosynthesis and gave off oxygen, which slowly filled the air over hundreds of millions of years.

• i.Entamoeba histolytica, a kind of amoeba that lives in water and food contaminated with feces.
• ii.Protista (it is a unicellular eukaryote).
• iii.With pseudopodia (“false feet”), which it pushes out from any point of its cell membrane; it flows around its food and encloses it in a food vacuole.
• iv.Any two: boil or filter the drinking water; wash hands with soap before eating and after using the toilet; keep food and water covered, away from flies and dirt.

• i.Ward 1’s road. Its slope is steep and bare, and with no drains the rainwater soaks into the loose soil, which becomes heavy and slides.
• ii.The environmental aspect. The soil tipped into the river harms the river’s life, and the landslides it causes block or wash away the road itself, so the village loses its road and its money is spent on repairs again and again (the economic and social aspects suffer too).
• iii.Bioengineering. The roots of the bamboo and grass bind the soil, and the plants slow down the water running over the slope, so the slope holds.
• iv.No. Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs. Ward 2’s road will last for many monsoons and serve the village for generations, while the cheap road must be repaired every year or may be swept away, so in the end it costs more.

• i.On a sunny day the slopes heat up faster than the air in the valley, and from late morning warm air flows strongly up the valley (a valley wind), a convection current. In the Kali Gandaki valley this wind is so strong that flights are planned for the early morning, before it starts.
• ii.Heated air expands and becomes less dense than the cool air outside the balloon, so the balloon full of hot air rises, just as warm water rises in a beaker.
• iii.Land heats up faster than water, because water has a much higher specific heat capacity. The air over the land is heated, expands and rises, making low pressure there, and the cooler, denser air over the lake flows in to take its place: a lake breeze, like a sea breeze.
• iv.Directly above a fire we get the hot air rising from it by convection as well as its radiation; at the side, the hot air doesn’t come towards us, and only radiation reaches us.

• i.Acetic acid. It turns blue litmus red.
• ii.Carbon dioxide. Bubbled through clear lime water, it turns the lime water milky.
• iii.Calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide

$$\text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2$$
iv. Carbon dioxide neither burns nor helps things burn. It covers (smothers) the fire and keeps the air (oxygen) away from it, so the fire goes out.