City and Guilds 8202 L2 Scientific Principles

The SI system of measurement is split into two groups; base units and derived units. what is meant by the term derived units?

• Combination of the five base units by a system of addition and subtraction calculations.

• Combination of the seven base units by a system of addition and subtraction calculations.

• Combination of the five base units by a system of multiplication and division calculations.

• Combination of the seven base units by a system of multiplication and division calculations.

How do we calculate an area?

• length x width

• length x width x height

• length x width x height x 1000

• Force(mass (kg) x acceleration (m/s²))

What is the equivalent metric pipe diameter to imperial 1"?

• 15mm

• 22mm

• 28mm

• 35mm

What is meant by the term 'relative density'?

• Relative density is the ratio of the density of a substance to the density of a standard substance under specific conditions.

• Comparison of different substances to each other

• Comparison to other substances at -273.15 ^oC (0^oK)

• Comparison of substances to sea water at sea level.

Pure metals are derived directly from the ore and contain small amounts of impurities. What are these metals?

• Steel, stainless steel, brass, gunmetal, pewter.

• iron, copper, aluminium, lead, zinc, tin

• cast iron, pig iron, wrought iron, low carbon steel.

• tool steel, spun iron, low carbon steel

What are the five main types of plastic used in the plumbing industry?

• Bakelite, polyester, nylon, polythene, rayon

• uPVC, polyethylene, polypropylene, polybutylene, ABS

• mdpe, hdpe, polyester, nylon, polypropylene

• uPVC, mdpe, nylon, polythene, rayon

The Mohs hardness scale lists materials in a range of hardness 1-10, which material is at 1 on the scale and which one is at 10?

• gypsum and titanium

• feldspar and quartz

• corundum and calcite

• talc and diamond

Dezincification is a type of corrosion that happens to what material?

• Copper

• Zinc

• Tin

• Brass

Erosion corrosion occurs in tubes and fittings due to the effect of fast flowing fluids and gases. What can accelerate this type of corrosion?

• Poor workmanship, ends not cut square or deburred, excess solder.

• Use of leaded solder and acid flux

• excess PTFE tape in threaded joints

• lack of pipe sealant and corrosion inhibitor

For galvanic corrosion to occur, three conditions must be present, these are?

• electrochemically similar metals must be present, these metals must be in electrical contact, these metals must be exposed to an electrolyte

• electrochemically similar metals must be present, these metals must not be in electrical contact, these metals must not be exposed to an electrolyte

• electrochemically dissimilar metals must be present, these metals must be in electrical contact, these metals must be exposed to an electrolyte

• electrochemically disssimilar metals must be present, these metals must not be in electrical contact, these metals must not be exposed to an electrolyte