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Behaviour and Expectations Line up in a single line outside the classroom quietly before the second bell No eating or drinking in the lab (this includes brain food) Bring required things to class Put rubbish in the bin Follow laboratory safety rules during practicals At the end of the lesson, stand in silence until you are dismissed Complete all set homework – this will be checked!

What to bring to Science Blue/Black/Red Pens Highlighters Glue Stick and Scissors Ruler Rubber Sharpener Grey lead pencil Charged Laptop: Pearson e-book IntoScience Science exercise book Practical book Planner/Student Diary

Making things bigger Module 2.1 (page 46)

Microscopes All living things are made up of cells Cells are microscopic, can’t be seen with the naked eye. Small things need to be magnified or made bigger so that they become visible to us. Scientists use microscopes to do this. Objects that can only be seen using a microscope are called microscopic. Microscopes

Two types of microscope Light microscope: compound (magnify thing about 1000 times) dissecting (magnify things about 100 times) 2. Electron microscope: magnify things about 1,000,000 times Two types of microscope

Monocular Binocular Stereo or Dissecting

Light Microscopes These are used in schools. Light from a mirror or a lamp passes through the specimen or object. The specimen must be thin so that the light can pass through it. The light then passes through the lenses that make the specimen look larger. Light Microscopes

Electron microscopes Electron microscopes are more powerful than light microscopes Allows specimens to be magnified up to a million times Beams of tiny particles called electrons are used rather than light Images are shown in black & white Two types of electron microscope  TEM & SEM

Comparison Light Microscope Electron Microscope Advantages Disadvantages Cell can be alive Not high magnification Easy to prepare Light must be able to pass through – very thin specimen Sometimes need to be stained Comparison Electron Microscope Advantages Disadvantages High Magnification Cell needs to be prepared Can see structures & organelles Images are black and white

Complete the Using a Microscope Worksheet Use the interactives on the class website, to complete the microscope worksheet Complete the Using a Microscope Worksheet

Label the following parts of the microscope with their correct name Ocular lens Label the following parts of the microscope with their correct name Course Focus Fine Focus Objective lens Arm Stage Mirror/Lamp

Match the part of the microscope with its description   Part of the microscope on which the specimen is placed Sharpens the focus on high magnification The lens of the microscope closest to the specimen The part of the microscope you look through Used to reflect light through the specimen Used to focus the microscope on low power Used to carry the microscope Stage Match the part of the microscope with its description Fine focus Objective lens Ocular lens Mirror Coarse focus Arm

Viewing a slide under a microscope Place on low power (what is the magnification) Look through the eyepiece and turn on the light and see as a circle of light Place the object/slide on the stage under the clips. Look at the microscope side-on and use the coarse focus knob to wind the body tube to its lowest point just above the slide. Look through the eyepiece and, with the fine focus knob, wind the body tube upwards away from the slide until the slide is in focus. Never move the objective lens down when looking down the microscope Draw what you see under low power Once in focus, turn it to a higher power (magnification) and bring the object into focus using the fine focus knob. What is the new magnification of the slide now? Record this in your results section.

Very small measurements Objects viewed under the microscope are smaller than 1mm. The unit of measurement used to measure microscopic objects is the micrometre (µm) There are 1,000 micrometres in 1 mm. If a cell is 50 micrometres across, how many would you observe if your field of view was 2 mm? Very small measurements 1mm: (50 x 1000) = 50 000 cells 2mm: (50 000 x2) = 100 000 cells

A blow fly: actual size - no magnification Magnification refers to how much larger a sample appears to be compared to its actual size. As magnification level increases, the amount of specimen you see gets smaller because you are zooming in A blow fly: actual size - no magnification x5 magnification Magnification x20 magnification x50 magnification

Calculating magnification You view the specimen through two lenses: the ocular lens (eyepiece lens) and one of the objective lenses. The total magnification can be calculated by multiplying the magnification of the eyepiece lens with the magnification of the objective lens. Total Magnification = Ocular lens x Objective lens Calculating magnification

Calculating magnification

Calculating magnification Ocular lens Objective lens Total mag x 10 x4 A? x 2 x5 B? C? x 20 100 D? 800 x10 E? 80 40 Calculating magnification 10 x5 x40 x8

Making a wet mount slide Preparing a Wet Mount Place the specimen in the center of a clean, grease-free microscope slide. Cover the specimen with a drop of water or other suitable mountant such as glycerol. Hold a coverslip at an angle so that its bottom edge is in contact with the drop on the slide. Use a mounted needle to support the coverslip and lower it gently over the specimen. This avoids including air in the mount. Making a wet mount slide Mounted needle Specimen Coverslip Mounting fluid Glass microscope slide

Rules for drawing microscope diagrams Label your diagram or specimen (heading) Record the magnification. Draw what you see with one eye still viewing the specimen down the microscope Draw only a few cells Draw large diagrams (1/3 of a page) Use a grey lead (never colour) or pen Use solid lines (no shading) All labels on the same side (if you can), use a ruler, labels to the right.

Example

drawing microscope diagrams CORRECT INCORRECT

Review Questions (page 52)