Experiment Lehrerheft description/manual. Heat. With. worksheet

Transcription

1 Experiment Lehrerheft description/manual zur Experimentierbox Heat With worksheet

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3 Science kit Heat Order no This Science kit is recommended for students at the age of Contents List of components...4 Storage plan Experiments Experiment 1: Heating and cooling water Experiment 2: Heating and cooling methylated spirits Experiment 3: How does a thermometer function? Experiment 4: What is a thermometer for? Experiment 5: The Celsius scale Experiment 6: Taking temperature measurements and reading exercises Experiment 7: Converting a liquid into a gas Experiment 8: Water evaporates, vaporizes too Experiment 9: Vaporizing liquids are cooling Experiment 10: Can a gas be re-converted into a liquid? Experiment 11: What happens when steam cools down? Experiment 12: The water cycle Experiment 13: How water particles unite Underlying principles...11 Worksheet Cornelsen Experimenta, Berlin All rights reserved. The work and parts of it are protected by copyright. Every use for other than the legal cases requires the previous written agreement by Cornelsen Experimenta. Hint to 46, 52a UrhG: Neither the work or parts of it are allowed to be scanned, put into a network or otherwise to be made publicly available without such an agreement. This includes intranets of schools or other educational institutions. Cornelsen Experimenta products are designed for educational use only and are not intended for use in industrial, medical or commercial applications. We assume no liability for damages which are caused by inappropriate usage of the equipment. 3

4 List of components Illustr. no. Qty. Description Order no Glass tubes, 220 x 6 mm Ø Droppers, plastic Candles in metal holders Thermometers, without graduation Thermometers, -3 C to +103 C Atomizer Food colouring, blue Food colouring, red Food colouring, yellow Insulating cases for beaker Beakers, 100 ml, plastic, with graduation Erlenmeyer flasks, glass, heat resistant, 25 ml Safety pins, 40 mm Red pegs Yellow pegs Blue pegs Immersion heater, 300 W/230 V Funnel, plastic, 70 mm Ø Tube brush Beaker, glass, 250 ml, heat-resistant, with graduation Plastic containers for activities Rubber stoppers with bore Bridge-shaped stands Thermometer model for demonstration Enclosed printed material 1 Experiment description/manual Heat Storage plan Heat Additional set Heat 2 3 Thermos flasks (For the transportation of hot water and ice cubes into the classroom.) Please note: Some experiments of the Science Kit Heat use an unshielded flame or an immersion heater as heating source. Therefore all experiments have to be accomplished with a maximum of accuracy and cautiousness to prevent accidents like burns or scalds. Heated elements must cool down before being restored in the kit. 4

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6 1 Experiments 1.2 Experiment 1 Heating and cooling water Fill the Erlenmeyer flask to the brim with (coloured) water. The rubber stopper is then inserted in the flask. The glass tube is inserted in the hole in the stopper, which causes the water to rise in the glass tube. The level of the liquid in the tube is marked using the blue plastic peg. Now place the flask, filled with water, on the bridge-shaped stand and heat it using a candle in a metal holder. As it is heated the level of the water in the tube rises, because its volume is increasing. The new water level is marked with a red peg. To cool the flask, place it in the plastic beaker, which should be filled with cold water, and possibly ice cubes as well. Materials: 1 glass tube (1) 1 candle in metal holder (3) 1 food colouring (7) 1 plastic beaker (9) 1 Erlenmeyer flask (10) 1 peg, red (12) 1 peg, blue (12) 1 rubber stopper (18) 1 bridge-shaped stand (19) Additionally: 1 thermos flask containing cold water or ice cubes 1.3 Experiment 2 Heating and cooling methylated spirits (inflammable!!) The Erlenmeyer flask is filled to the brim with coloured methylated spirits. Then the rubber stopper is inserted in the flask. The glass tube is inserted in the stopper. Because methylated spirits is inflammable for heating the spirits we do not use any candles. Instead a beaker filled with hot water is placed in the insulating case. Then the Erlenmeyer flask with rubber stopper and glass tube is placed in the plastic beaker. As it expands the methylated spirits rises up the glass tube. When it cools the level falls again. When heated, methylated spirits expands more than water. Materials: 1 glass tube (1) 1 food colouring (7) 1 insulating case (8) 1 plastic beaker (9) 1 Erlenmeyer flask (10) 1 rubber stopper (18) Additionally: 1 thermos flask containing hot water (70 C), 1 thermos flask containing cold water or ice cubes, methylated spirits 6

7 1.3 Experiment 3 How does a thermometer function? The thermometer without graduation is alternately dipped into the beakers containing water at different temperatures. The thermometer functions in the same way as the equipment set up in experiments 1 and 2: when it is heated the alcohol in the thermometer expands, and it contracts as it cools. Materials: 1 thermometer without graduation (4) 2 plastic beakers (9) Additionally: 1 thermos flask containing hot water, 1 thermos flask containing ice cold water 1.4 Experiment 4 What is a thermometer for? Fill the beakers with water at varying temperatures: approx. 55 C, 25 C and ice cold. Test the temperature by placing your hand in it. Water at 25 C feels cold if your hand has previously been held in hot water. However, if you first place your hand in cold water and then in water at 25 C, the water feels warm. If a thermometer is used to measure the temperature it will always indicate the same temperature in the lukewarm water, regardless of whether it has been held in hot or cold water beforehand. Therefore, thermometers have to be used for exact temperature measurements. Materials: 1 thermometer, 3 C to +103 C (5) 3 insulating cases for beaker (8) 3 plastic beakers (9) Additionally: 1 thermos flask containing hot water, 1 thermos flask containing ice cold water, tap water 1.5 Experiment 5 The Celsius scale The Celsius scale is defined between two specific temperatures, the melting point of ice (0 C) and the boiling point of water (100 C). On a thermometer without graduation these two temperature points can be determined as follows: The teacher fills a large heat-resistant beaker with water. An immersion heater is used to bring the water to boil. (Never use the heater without any water!) Each group places the thermometer without graduation into the boiling water and waits until the liquid in the thermometer stops rising. This point is to be marked with a red peg. Then the pupils fill the plastic beaker with water and ice cubes. They place the thermometer in the water and wait until the liquid in it stops moving. This point is to be marked with a blue peg. 7

8 Compare with the thermometer with Celsius scale, which shows 100 equal divisions between the marked two points (0 C to 100 C). Materials: 1 thermometer without graduation (4) 1 thermometer -3 C to 103 C (5) 1 plastic beaker (9) 1 red peg (12) 1 blue peg (12) 1 immersion heater (13) 1 beaker, heat-resistant (16) Additionally: 1 thermos flask containing hot water, 1 thermos flask containing ice cold water 1.6 Experiment 6 Taking temperature measurements and reading exercises The thermometer can be used to measure different temperatures e.g. classroom temperature, temperature of cold and warm water, hot tea, temperature of bulb after light has been switched on for a few minutes etc. For reading exercises and entries the worksheet at the end of this manual should be photocopied. Material: 1 thermometer, -3 C to +103 C (5) 1.7 Experiment 7 Converting a liquid into a gas Close the Erlenmeyer flask with the rubber stopper, invert it and place on the stand. Place a drop of Eau-de-Cologne or methylated spirits on the middle of the base of the flask using a dropper. The drop becomes smaller and smaller until it is no longer visible. The liquid has vaporized/evaporated. It has turned into a gas. A gas consists of tiny particles, invisible to the naked eye. However, it is sometimes possible to smell these particles even when the liquid has evaporated completely, e.g. in the case of Eau-de-Cologne or methylated spirits. Materials: 1 dropper (2) 1 Erlenmeyer flask (10) 1 rubber stopper (18) 1 bridge-shaped stand (19) Additionally: Eau-de-Cologne or methylated spirits 8

9 1.8 Experiment 8 Water evaporates, vaporizes too The Erlenmeyer flask is set up as in experiment 7 but now a drop of water is placed on its base. In this case too, the drop of water evaporates after a while even though this happens slower than it did in experiment 7. (Different liquids evaporate at different speeds.) Examples of water vaporization/evaporation in every-day life: Wet laundry dries Rainwater on car windows (the drops gradually become smaller and smaller until the window is completely dry) Water in an aquarium evaporates (water must be added from time to time) Materials: 1 dropper (2) 1 Erlenmeyer flask (10) 1 rubber stopper (18) 1 bridge-shaped stand (19) Additionally: some water 1.9 Experiment 9 Vaporizing liquids are cooling With a thermometer you determine the room temperature and the temperature of methylated spirits (inflammable!) filled in a plastic beaker. As the thermometer is pulled out of the liquid the temperature shown by the thermometer is decreasing. (Due to the evaporating methylated spirits on the thermometer.) This cooling effect can also be felt by wetting a finger with methylated spirits. Materials: 1 thermometer, -3 C to +103 C (5) 1 plastic beaker (9) Additionally: methylated spirits 1.10 Experiment 10 Can a gas be re-converted into a liquid? Add some hot water (at least 70 C) to the Erlenmeyer flask. Close the flask with a rubber stopper. The glass fogs up. The water particles which have evaporated deposit on the glass. A gas has been converted into a liquid. Materials: 1 Erlenmeyer flask (10) 1 rubber stopper (18) Additionally: 1 thermos flask or glass with very hot water 9

10 1.11 Experiment 11 (Demonstration) What happens when steam cools down? Fill a heat-resistant beaker with water and bring the water to the boilingpoint with an immersion heater. Now hold the plastic container filled with ice cubes over the steam. The water boils. Numerous particles escape from the water, some of which rise as gas bubbles (steam). The steam becomes mist (clouds) in the cooler air as the particles become more densely packed. Drops form on the cool base of the container. They condense. Materials: 1 immersion heater (13) 1 heat-resistant beaker (16) 1 plastic container (17) Additionally: 1 thermos flask with ice cubes 1.12 Experiment 12 The water cycle Water evaporates everywhere: Invisible water particles rise from the sea, from fields and forests. These evaporated water particles condense where the air is colder and form (mist) clouds. When the air becomes even colder or the wind moves these clouds to cooler regions, the mist particles unite to form larger drops which, because of their weight, fall downwards: It rains. The water cycle is complete. The rain evaporates, the invisible particles rise etc. 10

11 1.13 Experiment 13 How water particles unite Fill the atomizer with water. Spray the water onto a window or blackboard from a distance of approximately 30 cm. The tiny particles from the atomizer form a barely visible water cloud, but on the sprayed surface they unite after a while and form drops of increasing size. Materials: 1 atomizer (6) Additionally: some water 2 Underlying principles Heat and thermometer When solid bodies, liquids or gases are heated their volume (the amount of space that they occupy) generally increases. For example, when warmed by 1 degree Celsius (= 1 Kelvin), 1 litre of water and 1 litre of mercury both expand by 0,2 millilitre (= 0.2 cubic centimetre), alcohol by 1.1 millilitre (= 1.1 cubic centimetre). When cooled, the volume decreases again. However, if water (under normal pressure) is cooled, its volume only decreases until it reaches 4 C (Celsius). If the water is cooled further to 0 C its volume increases again. When water at 0 C changes to ice at 0 C there is a sudden increase in volume. This they cool and solidify. Temperatures are measured using thermometers. Liquid thermometers consist of a liquid-filled container (the bulb) connected to a very narrow tube. If the temperature rises, the liquid will expand. The level of the liquid in the tube at any given time can be read from a scale. Thermometers are usually filled with alcohol or mercury. On the Celsius thermometer scale the freezing point of water is marked at zero degrees Celsius (0 C), and the boiling point of water at 100 degrees Celsius (100 C). On the Fahrenheit thermometer scale the freezing point of water is shown as +32 F and the boiling point of water as +212 F. Readings in degrees Fahrenheit are still used in Britain and North America. The clinical thermometer Whereas outdoor, room and bath thermometers always show the temperature to which they are being exposed, the clinical thermometer is a so-called maximum thermometer. In other words, once the reading has reached its highest level, it remains there. This is achieved by means of a constriction between the bulb and the tube. As the mercury expands it is able to pass through this constriction, but as it cools it retracts, causing a break in the thread of mercury at this point. This enables a permanent reading. Only by shaking the clinical thermometer the liquid is forced back through the contriction into the bulb. 11

12 Some selected temperatures in degrees Celsius ( C) 6000 surface of the sun 2500 filaments in a lamp 1535 iron melts 1063 gold melts 950 to 1200 flame of gas burner 800 match flame 357 mercury boils 327 lead melts 270 electrical soldering iron 220 smoothing iron (linen setting) 100 water boils 78 alcohol boils 57,8 highest air temperature ever measured on Earth 36 to 37 body temperature of healthy human being 0 water freezes -39 mercury solidifies -89,2 lowest air temperature ever measured on Earth -180 air liquefies -273 lowest possible temperature (absolute zero) Evaporation The conversion of a substance from the liquid state into the gaseous state is referred to as evaporation. There are two methods of evaporation: boiling and vaporization. If water is heated to 100 C, bubbles rise to the surface because the water particles start moving rigorously as a result of the heat supply. The water boils. The rising bubbles contain an invisible gas: water vapour. Vaporization is the name given to the process when a liquid evaporates at a temperature below its boiling point. In this case, only particles on the liquid surface enter the gaseous state. Condensation The reverse process to evaporation, i.e. the conversion of a substance from the gaseous state into the liquid state, is known as condensation. Small droplets of liquid form from the invisible gas over the boiling water upon cooling and can be observed as a cloud or mist. 12

13 1 Reading exercises Heat Write down the temperatures shown by the thermometers. Worksheet Cornelsen Experimenta 13

14 Additional set Heat 2 Insulated wide neck vessels, 3 pcs. For the appropriation of warm and cold water as well as ice cubes for thermometer- and temperature-compound experiments. In a storage tray with lid. Content of each vessel: 1 liter Order no

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16 Experiment description/manual Heat Order no Holzhauser Straße 76 Tel.: info@corex.de D Berlin/Germany Fax: Internet: Cornelsen Experimenta, Berlin 03.00