Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 20 · 40 questions

What you do (Heat shows the secret): 1. Dip a cotton bud in lemon juice and write a secret message on white paper. 2. Let the paper dry completely — the writing disappears. 3. An adult irons the paper on a low setting while you watch from a safe distance. 4. Read the brown message and wash your hands.

1. 1.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a magnet (c) white paper (d) an adult with an iron
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) white paper (c) a cotton bud (d) turmeric powder
3. 3.🍋 Secret message: who does this step — ironing the paper? (a) an adult does it (b) a child can do it
4. 4.🧺 Which of these is needed for the secret lemon message? (a) lemon juice (b) yeast (c) turmeric powder (d) a battery cell
5. 5.True or false: cutting the lemon is a job a child can do. (a) True (b) False
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we keep it the same (b) we change it (c) we measure it
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) blue (d) brown
9. 9.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) the same paper (c) how dark the writing is
10. 10.🔍 Which is the odd one out? (a) plugging in the iron (b) ironing the paper (c) writing the message (d) putting the iron away
11. 11.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) white paper (c) an adult with an iron (d) a mirror
12. 12.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
13. 13.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) any child (c) whoever is fastest (d) only an adult
14. 14.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it is magnetic (c) it is cold (d) it can burn skin
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is kept the same. (a) True (b) False
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is what we measure. (a) False (b) True
17. 17.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the same cotton bud (b) the kind of juice (c) how dark the writing is
18. 18.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we measure it (b) we keep it the same (c) we change it
19. 19.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) writing the message (c) putting the iron away (d) reading the message
20. 20.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) a rainbow (b) dark brown words (c) blue words (d) almost nothing
21. 21.🍋 Why does the lemon writing turn brown with heat? (a) heat adds colour (b) the juice scorches first (c) paper turns lemony (d) the iron is brown
22. 22.🍋 Why can’t you see the lemon writing once it dries? (a) it turned into air (b) dry juice is see-through (c) the ink is magnetic (d) the paper ate it
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) a magnet (b) a small bowl (c) a cotton bud (d) white paper
24. 24.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) lemon juice (d) a mirror
25. 25.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
26. 26.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
27. 27.True or false: cutting the lemon is a job for an adult. (a) True (b) False
28. 28.True or false: a cotton bud is not needed for the secret lemon message. (a) True (b) False
29. 29.True or false: plugging in the iron is a job for an adult. (a) True (b) False
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is kept the same. (a) False (b) True
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the kind of juice (c) the same cotton bud (d) how dark the writing is
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is the one thing we change. (a) True (b) False
33. 33.🍋 Secret message: who does this step — putting the iron away? (a) an adult does it (b) a child can do it
34. 34.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) writing the message (d) cutting the lemon
35. 35.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
36. 36.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) wash your hands (d) skip washing
37. 37.True or false: putting the iron away is a job for an adult. (a) False (b) True
38. 38.🔍 Which is the odd one out? (a) reading the message (b) letting the paper dry (c) ironing the paper (d) writing the message
39. 39.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) putting the iron away (d) ironing the paper
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the iron setting (c) the kind of juice

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