Naep Science Grade 12

Explanation
The functional unit of the kidney is the nephron. Nephrons are responsible for filtering waste products from the blood, regulating fluid and electrolyte balance, and producing urine. Each kidney contains millions of nephrons, which consist of a glomerulus and a tubule. The glomerulus filters blood, while the tubule reabsorbs useful substances back into the bloodstream and excretes waste products. Overall, the nephron plays a crucial role in maintaining the body's internal environment by regulating water and electrolyte levels and removing waste products.

Explanation
Gall stones are not a disease of the kidney, but rather a condition that affects the gallbladder. They are formed when there is an imbalance in the substances that make up bile, leading to the formation of small, hard deposits in the gallbladder. These stones can cause symptoms such as abdominal pain, nausea, and jaundice, but they do not directly affect the kidneys. Kidney stones, on the other hand, are solid masses that form in the kidneys and can cause severe pain and other complications. Dropsy refers to the accumulation of fluid in the body, often caused by kidney disease. Diuresis is the increased production of urine, which can be a symptom of various kidney disorders.

Explanation
Pressure is defined as the force per unit area. It is a measure of how much force is applied over a given area. The equation for pressure is force divided by area. Therefore, pressure is the correct answer to the question "What is the force per unit area?"

Explanation
Coagulation is not a separation technique because it is a process in which particles come together to form larger clumps or aggregates, rather than separating them. In coagulation, substances are mixed together to cause the particles to stick together and settle out of a liquid suspension. This process is commonly used in water treatment to remove impurities. On the other hand, evaporation, filtration, and distillation are all separation techniques that involve the physical separation of different components of a mixture based on their properties such as boiling point, particle size, or solubility.

Explanation
Distillation is the process used in the production of ethanol. Distillation involves heating a liquid mixture to create vapor and then cooling the vapor to collect the desired substance in a separate container. In the case of ethanol production, distillation is used to separate ethanol from the fermented mixture. The mixture is heated, and the ethanol vaporizes at a lower temperature than other components. The vapor is then cooled and collected as pure ethanol. This process allows for the purification and concentration of ethanol, making it suitable for various applications such as fuel and alcoholic beverages.

Explanation
The unit of luminous intensity is candela. Candela is the SI unit for measuring the intensity of light perceived by the human eye. It is defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 x 10^12 hertz and has a radiant intensity in that direction of 1/683 watt per steradian. In simpler terms, candela measures the brightness of a light source.

Explanation
NaOH is not a salt because it is a strong base, not an ionic compound formed by the reaction of an acid and a base. Salts are typically formed by the combination of a metal cation and a non-metal anion, whereas NaOH is formed by the combination of a metal cation (Na+) and a hydroxide anion (OH-).

Explanation
The brain stem controls sneezing. Sneezing is a reflex action that is coordinated by the brain stem. When irritants enter the nasal passages, sensory receptors send signals to the brain stem, which then triggers the muscles involved in sneezing. The brain stem also regulates other involuntary actions such as breathing, heart rate, and digestion. The cerebrum is responsible for higher cognitive functions, the cerebellum controls motor coordination, and the hypothalamus is involved in regulating body temperature, hunger, and thirst.

Explanation
Oxy-acetylene is the correct answer because it is a mixture of oxygen and acetylene gases that is commonly used in welding. The high temperature flame produced by this mixture can melt and join metals together. Propyne, butane, and methane are not typically used in welding processes.

Explanation
The kidney is the correct answer because it is the primary organ responsible for urine production. It filters waste products and excess water from the blood to produce urine, which is then excreted from the body. The heart, lung, and brain do not play a direct role in urine production.