A science museum displays an old filament lamp beside a modern LED lamp. Fig. 1 shows a simplified section of the filament lamp. The filament is tungsten, a...
Question 1 Report
A science museum displays an old filament lamp beside a modern LED lamp. Fig. 1 shows a simplified section of the filament lamp. The filament is tungsten, a metal with a very high melting temperature. It is enclosed in a glass bulb containing a small amount of inert gas. When current flows, energy is transferred to the tungsten and its temperature rises until it glows. The glass is a covalent network solid and the copper wires are metallic.
(a) Name the type of bonding in tungsten. [1]
(b) Explain why tungsten is suitable for a hot filament. [2]
(c) What particles carry charge in the copper wires? [1]
(d) Describe why the glass bulb does not conduct electricity. [1]
A jeweller compares a gold ring with a brittle crystal of copper chloride. Fig. 1 shows part of the metallic structure of gold. The positive gold ions are arranged in rows and a cloud of electrons moves between them. The jeweller reshapes the ring by tapping it, without heating it. Gold is also chosen for electrical connectors because it carries charge and does not react easily with air or water.
(a) Name the bonding in gold. [1]
(b) Use Fig. 1 to explain why gold conducts electricity. [2]
(c) Describe what happens to layers of gold ions when the ring is hammered. [1]
Answer Details
Filament lamp
(a) Tungsten has metallic bonding. [1]
(b) Tungsten has strong metallic bonds, or strong attractions, in its structure. Much energy is needed to melt it, so it can withstand the very high temperature of a glowing filament. [2]
(c) Charge in the copper wires is carried by delocalised electrons. [1]
(d) Glass does not conduct because it has no mobile charged particles: its electrons are not free to move. [1]
Gold ring
(a) Gold has metallic bonding. [1]
(b) The delocalised electrons shown can move through the gold structure. These moving electrons carry charge, so gold conducts electricity. [2]
(c) When the ring is hammered, layers or rows of gold ions slide past one another. [1]
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