F2 1st Ter, 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		燃燒中的木條
2	Glowing splint		餘燼的木條
3	Hydrogencarbonate indicator		碳酸氫鹽指示劑
4	Lime water		石灰水
5	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	The glowing splint relights
	Lime water	The colour of the solution changes from colourless to milky.
	Hydrogencarbonate indicator	The colour changes from red to yellow
Water vapour	Dry cobalt chloride paper	The colour changes from blue to pink

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 to test for carbon dioxide.

The colour changes from red to yellow. / Use lime water and the colour changes from colourless to milky

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

Its colour changes from blue to pink.