Published on September 19, 2017
slide 1: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology S Sa af fe et ty y r ru ul le es s 1. Never work alone in the laboratory. 2. Unauthorized experiments are prohibited. 3. Report all injuries to your instructor at once. 4. When diluting concentrated acid or base always add the concentrated acid or base to water Not the other way round while stirring the solution. Be very careful with sulfuric acid. 5. Keep the laboratory desk clean and ordered. 6. Place unneeded books bags etc. on the shelves above your laboratory desk. 7. Waste containers are provided for the disposal of all solid chemicals and paper etc. 8. Always read the label twice before taking any chemical from a bottle. If you are not sure if you have the right chemical ask 9. Avoid using an excess of reagent. If you happen to have measured out too much see if someone else can use the excess. 10. Due to possible contamination of the contents of a whole stock bottle never return unused chemical to the stock bottle. 11. Always check your glassware before you use it. If it is broken or cracked exchange it for a new one. 12. If corrosive chemicals or liquids come in contact with the skin or clothing flood with copious amounts of water for an extended period of time. 1 13 3. . Spilled chemicals should be wiped up immediately spilled acid or base should be rinsed with plenty of water and wiped up with a sponge and the sponge rinsed afterwards. 1 14 4. . W Wh he en n y yo ou u a ar re e r re ea ad dy y t to o l le ea av ve e t th he e l la ab bo or ra at to or ry y y yo ou ur r l la ab bo or ra at to or ry y d de es sk k s sh ho ou ul ld d b be e c cl le ea an ne ed d. . L La ab bo or ra at to or ry y E Eq qu ui ip pm me en nt t N Na am me e D De es sc cr ri ip pt ti io on n a an nd d f fu un nc ct ti io on n D Dr ra aw wi in ng g Beaker Glass or plastic common sizes are 50ml 100ml 250ml and 400ml. Glass beakers may be heated. Florence flask Glass common sizes are 125ml 250ml and 500ml. They may be heated and they are used to hold Or pick up small objects. Test tube Glass. It’s used to store liquids. Watch glass To watch samples in the magnifying glass. Rubber stoppers To cover test tubes. slide 2: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology Metal spatula To catch powder substances. Wire gauze Metal. To support beakers or other equipment that may be heated with gas burner. Dropper pipet Glass tip with rubber bulb it’s used to transfer small volumes of liquid. Test-tube brush To clean test tubes. Mortar and pestle Porcelain it may be used to grind crystals and solid chemicals to a powder. Erlenmeyer flask Glass common sizes are 100ml and 250ml they may be heated and they are used in titrations Funnel Glass or plastic common size holds 125cm diameter filter paper. Gas Burner Made of metal connected to a gas supply with rubber tubing. It’s used to heat chemicals dry or in solution in beakers test tubes and crucibles. Graduated pipet Glass common sizes are 10ml or 25 ml. They are used to measure solution volumes less accurate than a volumetric pipet. Buret Glass common sizes are 25ml and 50ml. It’s used to measure volumes of solutions in titrations. Graduated cylinder It’s a glass tube with a base and it’s used to measure liquids. Test-tube holder Metal or wood. To catch test tubes or warm laboratory equipment. Petri dish Glass it’s used to grow bacteria or watch samples in the magnifying glass. slide 3: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology Tripod Metal. It’s used to support wire gauze. Microscope slide Glass to watch samples in the microscope. Slide cover Glass to cover samples before watching them in the microscope. slide 4: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology The Microscope Ocular or eyepiece lens: the lens at the top that you look through. Objective lens: or the lens closest to the object. Tube: Connects the eyepiece to the objective lenses. Arm: Supports the tube and connects it to the base. Base: The bottom of the microscope used for support. Illuminator: A steady light source that has a switch. Stage: The flat platform where you place your slides. Stage clips hold the slides in place. If your microscope has a mechanical stage you will be able to move the slide around by turning two knobs. One moves it left and right the other moves it up and down. It can be coarse and fine focus knobs. Revolving Nosepiece or Turret: This is the part that holds two or more objective lenses and can be rotated to easily change power. Diaphragm or Iris: Many microscopes have a rotating disk under the stage. This diaphragm has different sized holes and is used to vary the intensity of light that is projected upward into the slide. PROCEDURE AND RESULTS: A. PARTS OF MICROSCOPE: Name the parts of the microscope in the following drawing: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. slide 5: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology Steps to watch the sample through the microscope: 1. Place the slide on the stage and hold it with stage clips. 2. Switch on the light. 3. You have to start with the lowest power objective lens 4X first and while looking from the side crank the lens down as close to the specimen as possible without touching it. Now look through the eyepiece lens and focus upward only until the image is sharp. If you cant get it in focus repeat the process again. 4. Be careful not to wet the microscope. B. 1. Draw a very little F in a piece of paper and watch it through the microscope with the minor objective. 2. Compare the real F with the image watched through the microscope and an F watched through the mirrow: Real image Image watched through the mirrow Image watched through the microscope 3. What are the first objectives used to watch the sample 4. Are you watching a flat or embossed image through the microscope. Compare this image with the image watched through the binocular loupe. Is a flat or embossed image. Why do you think there are differences between the images 5. What happens when you move the sample to the right 6. Place the following objective. Is increasing or decreasing the field of vision Why do you think you have to place the sample in the center of field of vision when you change the objective 7. Write a list of materials that you have used in this laboratory practice. Microscope magnification power of the objective lens x power of the ocular lens slide 6: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology STEREOSCOPIC MICROSCOPE MATERIALS: RESULTS: A. Write the power of lenses: OCULAR: OBJECTIVES: Calculate the power of stereoscopic microscope: B. As you have learned the parts of microscope try to identify and describe the function of the following parts of the stereoscopic microscope: PARTS OF STEREOSCOPIC MICROSCOPE: Ocular or eyepiece lens: Ocular tube: Objective lens: Arm: Base: Illuminator: Stage: Stage clips: Focus control: Zoom control: Steps to watch the sample through the stereoscopic microscope: 5. Place the slide on the stage and hold it with stage clips. 6. Switch on the light. 7. Look through the eyepiece lens and focus upward only until the image is sharp. 8. Be careful not to wet the stereoscopic microscope. slide 7: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology C. Identify the parts of the stereoscopic microscope: 9. 11. 6. 8. 10. 5. 7. 1. 2. 3. 4. slide 8: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology Onion cells Objectives: Materials: Procedure: - Separate an inner layer of an onion and peel off the thin skin that is adhered to it. - Place a skin fragment on a microscope slide and dye it with a drop of methylene blue during five minutes. - Get the excess of colouring out and put the slide cover over the sample. - Clean the microscope slide without touching the sample. - Watch the sample in the microscope. Mouth cells Objectives: Materials: Procedure: - Scratch inside the mouth with a toothpick twice. - Place the sample in a microscope slide and put a drop of methylene blue during 5 minutes. - Get the excess of colouring out and put the slide cover over the sample. - Clean the microscope slide without touching the sample. - Watch the sample in the microscope. Results and conclusions: 1. Draw the sample and write the parts of the cell. 2. What magnifying power have you used to watch the sample 3. What differences are between the animal and plant cells 4. Write the objectives and materials of this laboratory practise. slide 9: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology N NU UT TR RI IE EN NT T I ID DE EN NT TI IF FI IC CA AT TI IO ON N Discover what can be found in food. You can determine the presence of some biological molecules starch proteins and fat using some easy chemical tests. MATERIALS: PROCEDURE: Firstly mash up solid food with a mortar and water. Pour the content into test tubes and use one for each chemical test. Presence of starch: Place some drops of iodine in test tube. If food has starch it will be violet almost black. Presence of proteins: Place food with the same volume of sodium hydroxide and copper sulphate in the test tube. It’s Biuret test. If food has proteins it will be violet-pink. Presence of fats: Place 1cm 3 of ethanol with small pieces of food in a test tube and shake it. Add 1cm 3 of water in the test tube. If you watch a white precipitate food will have fats or lipids. RESULTS AND CONCLUSIONS Complete the following table. Indicate if the chemical reaction is positive + or negative -. Food Starch Proteins Lipids slide 10: Laboratory practices 3 ESO IES N.1 CHESTE Biology and Geology DISSECTION OF A RESPIRATORY SYSTEM 1. OBJECTIVES: 2. MATERIALS: 3. METHOD: a. Draw the respiratory system and name its parts. b. Press the lungs to check that they are elastic and fluffy. c. Look at the trachea and identify the wall on the side of the oesophagus. d. Look at the bronchi. e. Blow in the trachea. What has happened f. Dissect the lung and look at the bronchioles. g. Place a piece of lung with water into the dissection tray. Try to keep it at the bottom. What has happened 4. RESULTS AND CONCLUSIONS: a. Draw the respiratory system and write the names of its parts. b. What type of tissues do these organs have c. Draw a cartilage of trachea. How do you identify the part of trachea that is next to the oesophagus d. Draw a cartilage of bronchi. Write the differences between bronchi and trachea. e. What has happened when you blew in the trachea Where has the air arrived f. Explain the last point of the method.