Page 10 - 新思维科学学生用书7 样章

1.1 Plant cells

Think like a scientist

Looking at plant cells through a microscope

This task gives you practice in using scientific equipment and doing practical work
safely.

You will need:
• a microscope, a microscope slide, a cover slip, a piece of onion bulb, tweezers
(forceps), a small sharp knife, a dropper pipette, a small container of water

Safety
Take care with the sharp knife. Cut the onion with the blade pointing away from you,

so that if it slips you don’t cut your fingers. 1 cut onion
1 Collect a small piece of onion. Cut out a
piece about 1 cm square. 2 drop of water
2 Use a dropper pipette to put a small

drop of water into the middle of a clean
microscope slide.
3 Very carefully, peel the thin layer from the
inside of your piece of onion.

4 Gently place the layer into the drop of water 3 peel
on the slide. Spread it out as flat as you can. 4 place on slide
5 Collect a very thin piece of glass called a
cover slip. (Take care – cover slips break

very easily!) Gently lower the cover slip over
your piece of onion on the slide. Try not to 5 cover
get air bubbles under the cover slip.
6 Turn the objective lenses on the microscope

until the smallest one is over the hole in the stage.
7 Put the slide onto the stage of the
microscope, with the piece of onion over
the hole.

8 Look down the eyepiece. Slowly turn the
focussing knob to move the lens away from
the slide. Stop when the piece of onion
comes into focus.

9 Make a drawing of some of the cells you
can see.

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