Mary Jones, Diane Fellowes-Freeman and Michael Smyth
Cambridge Checkpoint
Science
Challenge Workbook
9
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Contents Introduction 4 1 Plants
5
1.1 Floating discs experiment 1.2 Van Helmont’s experiment 1.3 The life cycle of a flowering plant
5 7 10
2 Living things in their environment
12
2.1 Investigating algae on a tree trunk 2.2 Arctic hares 2.3 Predator and prey populations
12 16 19
3 Variation and inheritance 3.1 3.2 3.3 3.4
Constructing a key The world’s most famous sheep Breeding goats in Ethiopia Bringing Darwin up to date
22 22 24 27 30
7 Salts 7.1 Investigating concentration 7.2 Salts, alkalis and equations 7.3 Mystery substances 8 Rates of reaction 8.1 Magnesium and hydrochloric acid 8.2 Which results are which? 8.3 As fast as possible 9 Forces in action 9.1 Density problems 9.2 Applying pressure 9.3 The effect of moments 10 Electricity
4 Material properties 4.1 What do the numbers tell you? 4.2 Atomic structure and trends 4.3 Comparing the trends in Groups 1 and 7 5 Energy changes 5.1 Exothermic reactions with metals 5.2 Dissolving potassium chloride 5.3 Using exothermic and endothermic reactions 6 Reactivity 6.1 6.2 6.3 6.4
How reactive are these metals? Which metal? Displacing metals Making use of displacement reactions
32 32 34 36 38 38 40 42 44 44 47 48 50
10.1 Charge 10.2 Current in circuits 10.3 Different types of circuit 11 Energy 11.1 Energy and fuel 11.2 Conduction 11.3 Investigating heat loss 11.4 Investigating radiation 11.5 Investigating evaporation
51 51 54 55 58 58 61 63 66 66 69 72 74 74 76 78 82 82 84 86 88 91
Introduction Welcome to the Cambridge Checkpoint Science Challenge Workbook 9 The Cambridge Checkpoint Science course covers the Cambridge Secondary 1 Science curriculum framework. The course is divided into three stages: 7, 8 and 9. You should use this Challenge Workbook with Coursebook 9 and Workbook 9. The tasks in this Challenge Workbook will help you to develop and extend your skills and understanding in science. This workbook is offered as extension to the main curriculum and therefore it does not cover all the curriculum framework content for this stage. The tasks will challenge you with scientific enquiry skills, such as planning investigations, interpreting and analysing results, forming conclusions and discussing them. They will also challenge you to apply your knowledge to answer questions that you have not seen before, rather than just recall that knowledge. If you get stuck with a task: Read the question again and look carefully at any diagrams, to find any clues. Think carefully about what you already know and how you can use it in the answer. Look up any words you do not understand in the glossary at the back of the Checkpoint Science Coursebook, or in your dictionary. Read through the matching section in the Coursebook. Look carefully at the diagrams there too. Check the reference section at the back of the Coursebook. There is a lot of useful information there.
Introducing the learners
Nor
Anna 4
Introduction
Amal
Elsa
Sam
Jon
Unit 1 Plants 1.1 Floating discs experiment This challenge task relates to 1.1 Photosynthesis from the Coursebook. In this challenge task, you will interpret the results of an experiment. You will think about variables, write a conclusion and use your scientific knowledge to explain a set of results.
Elsa and Nor do an experiment to investigate photosynthesis. They cut ten little discs out of a leaf, using a hole punch. Each disc is exactly the same size and is cut from the same leaf. They put one disc into water in a small beaker and shine light onto it. Little bubbles appear on the underside of the leaf disc. After a while, the bubbles of gas make the leaf disc float to the surface of the water. Elsa and Nor record the time taken for the leaf disc to float to the surface, then repeat their experiment with four more leaf discs. leaf disc
bubbles
1 Name the gas that the leaf disc produced when it photosynthesised. ……………………………………………………………………………………………………… 2 Explain why the bubbles of gas formed on the underside of the leaf, not on the top. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 3 In what way does the time taken for the leaf disc to rise depend on the bubbles of gas? Explain your answer. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………
1 Plants
5
Elsa and Nor do the investigation again, but this time they put the beaker and the leaf discs in a room with all the lights turned off. Here are the girls’ results.
Conditions Time taken for leaf disc to rise to the surface / s Try 1 Try 2 Try 3 Try 4 Try 5 Mean bright light
14
3
12
14
11
dim light
44
66
69
77
71
4 Suggest the question that the girls were testing. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 5 What was the independent variable in the girls’ experiment? ……………………………………………………………………………………………………… 6 Elsa thought that there was one anomalous result in each row of their results table. Draw circles around the two anomalous results in the table. 7 Calculate the mean times taken for each row in the results table, and write them in the last column.
Remember not to include the anomalous results when you calculate the mean.
8 Suggest why the times taken for the five leaf discs to rise in each of the lighting conditions were not all the same. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 9 Write a conclusion for the girls’ experiment. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 10 Suggest an explanation for the difference between the mean times for the leaf discs to rise in bright light and in dim light. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 6
1 Plants
Unit 1 Plants
1.2 Van Helmont’s experiment This challenge task relates to 1.3 Plants and water from the Coursebook. In this challenge task, you will look at the work of one of the first people to do scientific experiments, about 350 years ago. Then you will imagine you are this person and think about how to test your ideas.
Johannes Baptista van Helmont was born in Belgium in 1580. In 1648, he set up an experiment to try to find out what a willow plant uses to help it to grow. Van Helmont cut a shoot from a willow tree and weighed it. He found that it weighed 5 pounds.
A pound is an old unit of measuring mass. One pound is just under half a kilogram.
He dried some soil, weighed out 200 pounds of it, and put it into a very big pot. He sank the pot into the ground, and then planted the willow shoot in the soil. He covered the soil in the pot with a metal cover, with small holes to let water in. Over the next five years, van Helmont watered the willow plant whenever the soil got dry. Each autumn, the leaves fell off the plant, and new ones grew in the spring. After five years, he dug up the tree and weighed it again. He found that it weighed more than 169 pounds. He collected all of the soil in the pot, dried it, and weighed it. Its mass was just under 200 pounds. He did not weigh the leaves that fell off the plant each autumn. 1 Describe what van Helmont did well in his experiment. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 2 Describe how van Helmont could have improved his experiment. ……………………………………………………………………… ……………………………………………………………………… ………………………………………………………………………
Do not suggest other experiments he could have done; just suggest how he could have made this experiment better.
……………………………………………………………………… ………………………………………………………………………………………………………
1 Plants
7
55 years years
pounds 55 pounds
soil200 200 pounds pounds drydrysoil
169 pounds 169 pounds
drysoil soil200 200 pounds dry pounds
In 1648, no one knew anything about photosynthesis. Also, it was very rare for people to do scientific experiments to try to find answers to questions. No one had really worked out how to plan good experiments. Van Helmont’s conclusion was that 164 pounds of wood, bark and roots were produced from water alone. 3 Suggest how van Helmont’s reasoning led to this conclusion. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 4 Use your knowledge about photosynthesis to explain why van Helmont’s conclusion was wrong. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………
8
1 Plants
Unit 1 Plants Van Helmont did know that there were gases in the air. In other experiments, he discovered carbon dioxide, which he called ‘sylvestre’. He knew that ‘sylvestre’ was present in the gases produced when yeast ferments, and when charcoal was burnt. (Charcoal is made from wood.) However, it seems he did not link this knowledge to his willow tree experiment. 5 Imagine you are van Helmont. You have suddenly realised that the reason charcoal gives off ‘sylvestre’ when it is burnt might be because the tree took in ‘sylvestre’ as it grew. You have an idea that perhaps some of the increase in mass of the willow shoot was because it took in ‘sylvestre’ as it grew. Describe an experiment that you could do, as van Helmont and in the time that he lived, to see if your idea is correct.
This is a difficult challenge. Discuss your ideas with others before you plan what to write.
……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………
1 Plants
9
1.3 The life cycle of a flowering plant This challenge task relates to 1.4 Flowers, 1.5 Pollination and 1.6 Fertilisation from the Coursebook. In this challenge task, you will bring together what you have learnt about the parts, the life and the reproduction of a flowering plant.
The first diagram shows the life cycle of a flowering plant. The lower diagrams show three of the stages in this life cycle. 1 seed
5 fertilisation
2 plant with flowers
pollination 3 male gametes 4 female gametes
10
1 Plants
Unit 1 Plants 1 Look at the life cycle diagram on the previous page. Decide which numbered stage of the life cycle is shown in the other diagrams. Write the number from the life cycle diagram in the box next to the diagram that illustrates that stage. 2 Here are some descriptions of plant parts. For each one, write the name of the part that is being described. A Male gametes are made here. …………………………………………………………………… B Female gametes are made here. ………………………………………………………………… C This protects the seed while it is waiting to germinate. ………………………………………… D These parts attract insects to the flower. ………………………………………………………… E This will grow into a new plant when the seed germinates. ……………………………………… F This will develop into a seed after fertilisation is completed. …………………………………… G This receives pollen grains, which may have been brought by a bee. …………………………… H This is where pollen grains are made. …………………………………………………………… I This fuses with a female gamete to produce a zygote. …………………………………………… J This will develop into a fruit as the seeds form inside it. ………………………………………… 3 Now use the letters above to label the diagrams opposite. You may want to use more than one letter for some parts of the diagrams. You may want to use each letter more than once. Use label lines for your labels. Do not write on top of the diagrams.
1 Plants
11
Unit 2 Living things in their environment 2.1 Investigating algae on a tree trunk This challenge task relates to 2.3 Ecology from the Coursebook. In this challenge task, you will think about the design of an ecology experiment, and how to display and interpret the results.
Amal and Jon noticed that the trunks of the trees growing outside their school had green organisms growing on them. Their teacher told them these were algae, which are very small plant-like organisms.
I think there are more algae on the shady, northfacing sides of the tree trunks than on the sunniest sides.
Where Amal and Jon live (in the northern hemisphere), north-facing surfaces receive the least sunlight and south-facing surfaces receive the most.
The boys decided to collect data to decide whether Amal’s idea was correct. This is what they did: • They chose five trees growing in the same area. • They cut out a square piece of transparent plastic with sides of 10 cm. • They very carefully drew a 1 cm grid on the plastic. • They tied a string horizontally around the first tree trunk, exactly 1.5 m up from the ground. • They attached the grid to the string, on the north-facing side of the tree trunk. • They counted how many squares had algae in them. • Then they moved the grid along the string to the east-facing side, and counted again. • They repeated this on the south-facing and west-facing sides. • They did this for each of the five trees.
12
2 Living things in their environment
Unit 2 Living things in their environment
string grid
1 Describe how the boys could check which is the north-facing side of the tree. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 2 Explain why it was a good idea to tie a string around each tree at 1.5 m above the ground. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 3 Explain why it was a good idea to use a grid that was 10 cm × 10 cm, rather than a larger one or a smaller one. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………
2 Living things in their environment
13
Here are the boys’ results. Tree
Number of squares containing algae Facing north Facing east Facing south
Facing west
1
89
39
17
54
2
75
43
29
51
3
96
36
46
60
4
33
12
2
15
5
72
38
12
48
The boys discussed what to plot on a graph to display their results. I think we should calculate a mean for each tree, then plot a bar graph with the tree on the x-axis and the mean number of squares containing algae on the y-axis. Amal
I think we should calculate a mean for each of the four sides of the trees, then plot a bar graph with side of tree on the x-axis and mean number of squares containing algae on the y-axis. Jon
4 Who was right? Explain your answer. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 5 Complete the results chart above in the way that you have decided is best.
14
2 Living things in their environment
Unit 2 Living things in their environment 6 Use your results to draw a bar chart on the grid.
7 Write a conclusion for the boys’ experiment. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… 8 Suggest an explanation for the pattern shown in the results. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ………………………………………………………………………………………………………
2 Living things in their environment
15
2.2 Arctic hares This challenge task relates to 2.4 Food webs and energy flow from the Coursebook. In this challenge task, you will use information to convert some food chains into a food web. Then you will make a prediction and suggest how you could test it.
Here are four food chains involving Arctic hares. Arctic hare
Arctic willow
Arctic hare
purple saxifrage grasses An Arctic hare
Arctic willow
Arctic hare Arctic hare
1 Construct a food web from the four food chains.
16
2 Living things in their environment
snowy owl Arctic fox
gyrfalcon Arctic wolf
Arctic wolf Arctic wolf