F2 1st Term IS WS 02 Answers

1st Term WS 02 Submission date：_____________ Name：______________________ Class & no.：2 _________(     )

7.1       What is air made up of?

B. Identifying gases

i      Words to know:

	English term	Write the words again	Chinese term
1	Burning splint	Burning splint	燃燒的木條
2	Glowing splint	Glowing splint	帶星火的木條
3	Hydrogencarbonate indicator	Hydrogencarbonate indicator	碳酸氫鹽指示劑
4	Lime water	Lime water	石灰水
5	Cobalt chloride paper	Cobalt chloride paper	氯化鈷試紙

i      Fill in the blanks:

1        We can use a ­burning splint to test for oxygen. It       relights a glowing splint.

2        We can use lime water to test for carbon dioxide. Its colour changes from colourless to milky.

We can also use hydrogencarbonate indicator to test for it.

It changes from red to yellow.

3        Water and water vapour水蒸汽 can turn dry cobalt chloride paper from blue to pink.

4        Complete the following table about how we test for certain gases

	Testing material used	Test result
Oxygen	Glowing splint /burning splint	It relights
		It burns more brightly
Carbon dioxide	Lime water	The colour of the solution changes from colourless to milky.
	Hydrogencarbonate indicator	Its colour changes from red to
		yellow
Water vapour	Dry cobalt chloride	Its colour changes from blue to pink
	paper

i      Short questions:

1             What gas can relight a glowing splint? Oxygen

2             How can we test for carbon dioxide? Describe描述 the test result.

We can use hydrogencarbonate indicator (lime water) to test for carbon dioxide.

Its colour changes from red to yellow. (Its colour changes from colourless to milky)

3             What happens if a drop of water is put on a piece of dry cobalt chloride paper?

It turns pink from blue.