Photo AI
3 (a) Which of the following substances will be a solid at 20 °C and will melt when placed in a beaker of hot water at 80 °C? | | melting point in °C | boiling point in °C | |------|---------------------|---------------------| | A | 122 | 249 | | B | -7 | 59 | | C | 30 | 2403 | | D | -32 | 27 | (b) A student set up the apparatus shown in Figure 2 to obtain pure water from sea water by distillation - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2018 - Paper 1
Question 3
3 (a) Which of the following substances will be a solid at 20 °C and will melt when placed in a beaker of hot water at 80 °C? | | melting point in °C | boiling... show full transcript
Worked Solution & Example Answer:3 (a) Which of the following substances will be a solid at 20 °C and will melt when placed in a beaker of hot water at 80 °C? | | melting point in °C | boiling point in °C | |------|---------------------|---------------------| | A | 122 | 249 | | B | -7 | 59 | | C | 30 | 2403 | | D | -32 | 27 | (b) A student set up the apparatus shown in Figure 2 to obtain pure water from sea water by distillation - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2018 - Paper 1
Step 1
Which of the following substances will be a solid at 20 °C and will melt when placed in a beaker of hot water at 80 °C?
Answer
The only correct answer is C.
- A (122 °C) is incorrect because it will be a solid at 20 °C and will not melt.
- B (-7 °C) is incorrect because it will be a liquid at 20 °C and gas at 80 °C.
- D (-32 °C) is incorrect because it will also be a liquid at 20 °C and gas at 80 °C.
Step 2
Explain how the water in sea water separates to produce the pure water in this apparatus.
Answer
The process involves heating the sea water.
- When heated, the water boils or evaporates, leaving the salt behind. This forms water vapor.
- The water vapor rises, then cools down as it moves through the condenser, where it condenses to form pure water.
Thus, the salt is left behind while the water is collected as condensate.