Science Focus 2 - Coursebook Answers - Pearson Australia Media ...

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Answers to coursebook questions Chapter 1e Variable: factor that may affect an experiment.f Controlled variable: factor not changed in an experiment.2 a True.b False: Observations never involve guesswork.c True.d False: A variable is not the same as an inference.e True.f False: ‘The grass grew 5 mm in a day’ is a quantitative observation.g True.3 The three questions scientists ask when they are planning an experiment are:• What do I want to test?• What am I going to change?• What am I going to keep the same?4 Only one variable should be changed at the one time, otherwise the cause of anychange observed would never be known.Think5 a The observations made were: the TV wasn’t working; there was water on thetop; there was water underneath.b The inferences made were: the roof leaked; water got into the TV; the watershorted out the TV.c Predictions about the TV and room in the future were: the roof needs to berepaired; then the TV needs repair or replacement.6 a Variables in the race: footwear, spoon size, handbag, distance run, egg size,shopping bag.b This was not a fair race since there are too many different variables changing atonce.c It would be a fair race if variables were controlled by ensuring that both runnerswore the same footwear, used the same type of spoon and did not carry bags, bymaking the tracks the same lengths and by having the same-size egg.Analyse7 a The two variables that Carl tested were the amount of sunlight and the amount ofwater.b Other variables that may have affected the growth of the grass under the tentfloor were: the lack of carbon dioxide; trampling.c The previous knowledge Carl used in designing his experiments was thatphotosynthesis requires carbon dioxide and sunlight.8 a A suitable heading for Carl’s research project would be: ‘Why grass dies’.b Introductory sentences might be: Grass was found to die after a week of beingcovered by a tent floor. Lack of sunlight, water or carbon dioxide and tramplingcould have been factors.c The aim for the whole research topic is to find what variable was the mostimportant in killing the grass under a tent floor. Experiment 1 aim: To find if© Pearson Education Australia (a division of Pearson Australia Group Pty Ltd) 2005.This page from the Science Focus 2 Teacher’s Resource on CD may be photocopied for classroom use.
Answers to coursebook questions Chapter 1lack of sunlight kills grass in a week. Experiment 2 aim: To find if lack of waterkills grass in a week.d Conclusion for Experiment 1: A lack of sunlight kills grass in the way seenunder the tent floor.Conclusion for Experiment 2: A lack of water kills grass but not in the way thathappened under the tent.The conclusion for the whole research project is that a lack of sunlight causedthe death of the grass under the tent floor.Investigate9 Carl could make an educated guess (hypothesis) about the outcome of the grass andthen design an experiment to test the hypothesis. For example, he could decide thatthe grass could grow again if not deprived of sunlight for too long. The variable hewould then be testing would be number of days of sunlight or deprivation. Hisdependent variable would then be a range of days from perhaps 1 to 30. Hisindependent variable would require measurement of time needed for the grass to begreen again. The experiment might result in a cut-off point beyond which the grasscannot recover.Unit 1.3 Better measurementsCheckpoint1 An error is small and unavoidable; a mistake is avoidable with care.2 Errors occur due to human reflexes, human reading ability, accuracy of theinstrument itself and the temperature of the day. These errors vary with individualcapability and cannot be entirely avoided.3 Four types of errors: parallax, reading, instrument, human reflex.4 Scientists take multiple measurements to improve accuracy.Think5 a False: Errors make all measurements slightly inaccurate.b True.c False: A mistake is not an error.d False: A measurement of 56 ± 2°C is between 54°C and 58°C.e False: Human reflexes are not always fast and accurate.6 a The number of kangaroos in Australia: estimate.b The number of kangaroos in the zoo: accurate.c The duration of a science class at school: accurate.d The number of hours of cloudy days in the next month: estimate .e The number of students who buy chips at the school canteen: estimate.7 a Error.b Mistake.c Mistake.© Pearson Education Australia (a division of Pearson Australia Group Pty Ltd) 2005.This page from the Science Focus 2 Teacher’s Resource on CD may be photocopied for classroom use.
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Science Focus 2 - Coursebook Answers - Pearson Australia Media ...

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