Unit 1. Scientific activity

Transcription

1 Index Unit 1. Scientific activity 1. The scientific method Measurement Unit transformation Scientific notation Working in the lab...7 Practice exam...9 Page 1 of 11

2 1. The scientific method 1. Observation This step could also be called "research." It is the first stage in understanding the problem you have chosen. After you decide on your area of science and the specific question you want to ask, you will need to research everything that you can find about the problem. You can collect information on your science fair topic from your own experiences, books, the internet, or even smaller "unofficial" experiments. This initial research should play a big part in the science fair idea that you finally choose. 2.Formulation of hypothesis The next stage of the Scientific Method is known as the "hypothesis." This word basically means "a possible solution to a problem, based on knowledge and research." The hypothesis is a simple statement that defines what you think the outcome of your experiment will be. 3. Experiments This is the part of the scientific method that tests your hypothesis. An experiment is a tool that you design to find out if your ideas about your topic are right or wrong. It is absolutely necessary to design a science fair experiment that will accurately test your hypothesis. The experiment is the most important part of the scientific method. It's the logical process that lets scientists learn about the world. When you do the experiment it can be very useful express your data in charts and/ or graphs 4. Conclusion The final step in the scientific method is the conclusion. This is a summary of the experiment's results, and how those results match up to your hypothesis. This is an important point. You can not PROVE the hypothesis with a single experiment, because there is a chance that you made an error somewhere along the way. What you can say is that your results SUPPORT the original hypothesis. If your original hypothesis didn't match up with the final results of your experiment, don't change the hypothesis. Instead, try to explain what might have been wrong with your original hypothesis. What information did you not have originally that caused you to be wrong in your prediction? What are the reasons that the hypothesis and experimental results didn't match up? Remember, a science fair experiment isn't a failure if it proves your hypothesis wrong or if your prediction isn't accurate. No one will take points off for that. A science fair experiment is only a failure if its design is flawed. A flawed experiment is one that (1) Page 2 of 11

3 doesn't keep its variables under control, and (2) doesn't sufficiently answer the question that you asked of it. When a hypothesis is confirmed you can communicate it to the rest of the scientific community with Laws and theory Observation Hypothesis. All of the first stage of the Scientific Method -- the observation, or research stage -- is designed to help you express a problem in a single question ("Does the amount of sunlight in a garden affect tomato size?") Propose an answer to the question based on what you know. ( "I believe that the more sunlight a tomato plant receives, the larger the tomatoes will grow.) Experiments Conclusions The experiment that you will design is done to test the hypothesis. (Remember: if you changed the amount of light, AND changed the amount of water each plant received, you wouldn't know if the bigger tomatoes were because of the light, or the water! So it's absolutely critical to have everything be as close to identical or "controlled" as you can get it.) You have two options for your conclusions: based on your results, either (1) you CAN REJECT the hypothesis, or (2) you CAN NOT REJECT the hypothesis. 1.- Do the graph of the following data: Position (m) Time (s) a) Can you find a relationship between position and time? What is this? b) When the time is 6 s, what is the distance? If the position is 40 m, what is the time? Page 3 of 11

4 2.- Measurement Physics and Chemistry are based on the study of the properties of bodies that can be quantified, measured. Those properties are called physical quantities. Each physical quantity is always followed by a unit. There are two types of physical quantities: - Base quantities: they are self-defined, they can be worked out independently. - Derived quantities: they are obtained from a combination of the base The International System of Quantities (SI) lists seven base quantities: Quantity name unit symbol length metre m mass kilogramme kg time second s temperature kelvin K electric current ampere A luminous intensity candela cd amount of substance mole mol Some derived quantities are: area square metre m 2 volume cubic metre m 3 density kilogramme/cubic metre kg/m 3 speed metre/second m/s acceleration metre/second squared m/s Unit transformation. Writing of very high or low numbers can be simplified by using multiples and submultiples of the units, thus avoiding numbers with many digits. The mathematical procedure to be used is to convert these numbers using conversion factors. Tables of multiples or submultiples. Prefix Symbol Value Description Decimal Value tera (T) trillion giga (G) 10 9 billion mega (M) 10 6 million kilo (k) 10 3 thousand hecto (h) 10 2 hundred 100 deka (da) 10 1 ten one 1 deci (d) 10-1 tenth 0 1 centi (c) 10-2 hundredth 0 01 Page 4 of 11

5 milli (m) 10-3 thousandth micro (µ) 10-6 millionth nano (n) 10-9 billionth pico (p) trillionth E.g. : 2 hours into seconds = 2hours 3600 s 1hour = 7200 s Activities: 2. Transform the following units by means of conversion factors: a) 345 g into kg b) 2954 s into days c) 8560 mm into km d) 22 m 2 into cm 2 e) g into mg f) 7.85 mm 3 into dm 3 g) 32 min into hours Sol: a) b) c) d) e) 6.5 f) g) Write down : a) In centimeters a TV of 42 inches (1 inch = 2,54 cm) b) In square metres the surface of a kitchen table measuring cm 2. c) The distance between two cities (7 miles) in km (1Km is equivalent to miles. Sol: a) 106,68 b) 1.2 c) 11,26 km 4. Express in SI units a) 45 hm b) g c) 125 dm 3 d) 4 days e) 45 ma Sol: a) m b) kg c) d) s e) A For complex units we use two conversion factors: E.g. Page 5 of 11

6 90 Km/h a m/s= 90 Km/h 1000m 1Km. 1 hour 3600 s = 25 m/s 5. Transform the following units: a) 135 km/h into m/s b) 10 m/s into km/h c) 8400 kg/m 3 into g/cm 3 d) 7.6 g/ cm 3 into kg/m 3 e) 108 km/h into m/s Sol: a) 37.5m/s b) 36km/h c) 8.4 g/cm 3 d) 7600 kg/m 3 e) 30 m/s 2.2. Scientific notation. The result of a measurement can produce a very small or very big number, which is usually hard to read or uncomfortable to write. In order to express these figures simply we resort to scientific notation, meaning that we write a given figure by means of a decimal number with just one integer digit -the unitand a power of ten with a positive or negative exponent. E.g. - The distance between the Earth and the Sun is m = m - The mass of a hydrogen atom is kg 6- Express the following figures in scientific notation: a) m b) kg c) m d) cm e) 2500 A 7- Express the following figures in scientific notation and give the result with three significant digits, applying rounding rules when necessary: a) Page 6 of 11

7 b) c) d) e) f) g) h) i) j) Working in the lab Material lab: Page 7 of 11

8 Activities 9. Label the following 10. Complete the table material Use drawing Watch glass beaker spatula dropper Volumetric cylinder flask funnel Page 8 of 11

9 11. Label the following Page 9 of 11

10 Practice exam 1.- Define physical quantity. What is the difference between base quantities and derived quantities? Write three examples of base quantities and their units in the S.I. 2.-Transform the following units by means of conversion factors, to SI units: a) 83.2 km f) 360 mm b) 6 hours g) 20 ma c) 720 cm h) 15 mg d) 14,2 dam i) 112 hm e) 72 g j) 2 weeks 3º Transform the following units by means of conversion factors: a) 50 m/s a km/h b) 400 km/h a m/s c) 124 mm 2 a dm 2 d) 7630 kg/m 3 a g/cm 3 4º Name the stages of scientific method and explain briefly each one. Give an example. 5º Express the following figures in scientific notation and give the result with three significant digits, applying rounding rules when necessary: a) d) g) b) e) h) c) f) i) Page 10 of 11

11 Answers to the practice exam: 2ºa) m b) s c) 7.2 m d) 142 m e) 0.072kg f) m g) 0.02 A h) kg i) m j) s 3ºa) 180 km/h b)111.1 m/s c) dm 2 d) g/cm 3 5º a) = d) = g) = b) = e) = h) = c) = f) = i) = Page 11 of 11