Differentiate between element, compound, and mixture, and calculate the density of a block.

$$\text{Volume} = \text{length} \times \text{width} \times \text{height}$$ $$\text{Volume} = 5\, \text{cm} \times 3\, \text{cm} \times 2\, \text{cm}$$ $$\text{Volume} = 30\, \text{cm}^3$$

$$\text{Density} = \frac{270\, \text{g}}{30\, \text{cm}^3}$$ $$\text{Density} = \boxed{\text{9 g/cm}^3}$$

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:
($\alpha$) photosynthesis: Light energy is converted into chemical energy.
($\beta$) 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?
($\alpha$) Pipes: Sound is produced by the vibration of an air column inside the pipe.
($\beta$) 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)