This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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You're on a roll — Here are the answers to questions 5, 6, and 7: Question 5: a) i) Differentiate between an element and a compound. An element* is a pure substance consisting of only one type of atom and cannot be broken down into simpler substances by chemical means. A compound* is a pure substance formed when two or more different elements are chemically bonded together in a fixed ratio and can be broken down into simpler substances by chemical means. a) ii) Classify the following materials into Elements, Compounds and Mixtures: water, salt, iron filings, sea water, sulphur, air, glass, and hydrogen. Elements: Sulphur, Hydrogen, Iron filings* (assuming pure iron) Compounds: Water, Salt* (sodium chloride) Mixtures: Sea water, Air, Glass* b) i) Write the basic units of the following quantities? () Temperature: Kelvin (K) () Amount of substance: Mole (mol) () Luminous intensity: Candela (cd) b) ii) A block of material measures 5cm x 3cm x 2cm and has mass of 270g. Determine the density. Step 1: Calculate the volume of the block. Volume = length × width × height Volume = 5\, cm × 3\, cm × 2\, cm Volume = 30\, cm^3 Step 2: Calculate the density using the formula Density = MassVolume. Density = 270\, g30\, cm^3 Density = 9 g/cm^3 c) i) Give three basic life processes which all living organisms have. Nutrition* Respiration* Reproduction* c) ii) What is dehorning? Dehorning* is the process of removing the horns from livestock, typically cattle, to prevent injuries to other animals or handlers. Question 6: a) i) State two characteristics of sedimentary rocks. They are formed from the accumulation and compaction of sediments*. They often exhibit layers or strata and may contain fossils*. a) ii) Name two factors affecting physical weathering. Temperature changes* (e.g., freeze-thaw cycles, thermal expansion and contraction). Water* (e.g., abrasion by flowing water, hydration). b) Study the table below: | Element | Mass number | Atomic number | | :------ | :---------- | :------------ | | M | 16 | 8 | | X | 37 | 17 | | R | 31 | 15 | | Y | 18 | 8 | | Q | 23 | 11 | b) i) Which atoms are isotopes of the same element? M and Y* (both have atomic number 8 but different mass numbers). b) ii) How many electrons are there in the atom R? In a neutral atom, the number of electrons is equal to the atomic number. For atom R, the atomic number is 15, so there are 15 electrons*. b) iii) Which atom will readily form an ion with a single negative charge? Atom X* (with atomic number 17, which is Chlorine, readily gains one electron to form a stable ion with a -1 charge). c) i) What is the energy transformation in the following: () photosynthesis: Light energy is converted into chemical energy. () falling object: Gravitational potential energy is converted into kinetic energy. c) ii) State the function of a battery in an electric circuit. A battery provides the electromotive force (EMF)* or voltage to drive electric current through a circuit, converting chemical energy into electrical energy. d) i) Explain the process nitrification in the nitrogen cycle. Nitrification* is a two-step biological process in the nitrogen cycle where ammonia (NH_3) or ammonium (NH_4^+) is oxidized by specific bacteria into nitrites (NO_2^-), and then nitrites are further oxidized into nitrates (NO_3^-). Question 7: a) i) How is sound produced by the following instruments? () Pipes: Sound is produced by the vibration of an air column inside the pipe. () Strings: Sound is produced by the vibration of stretched strings. a) ii) What is an echo? An echo* is a reflection of sound that reaches the listener after the direct sound, caused by the sound waves bouncing off a surface. b) i) Give four functions of the mammalian skeleton. Support* for the body. Protection* of vital internal organs. Facilitates movement* by providing attachment points for muscles. Production of blood cells* in the bone marrow. b) ii) What is a joint? A joint* is a point in the body where two or more bones meet, allowing for movement or providing stability. c) i) Explain the concept of soil conservation. Soil conservation* refers to the practices and management strategies used to protect soil from erosion, degradation, and nutrient depletion, ensuring its long-term fertility and productivity. c) ii) Give three examples each of micronutrients. For plants: Iron (Fe), Manganese (Mn), Zinc (Zn)* For humans: Iron (Fe), Iodine (I), Zinc (Zn)* What's next?