Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 501 · 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.True or false: white paper is needed for the secret lemon message. (a) False (b) True
2. 2.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) white paper (c) turmeric powder (d) lemon juice
3. 3.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) skip washing (c) wash your hands (d) lick your fingers
4. 4.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) yeast (c) an adult with an iron (d) a small bowl
5. 5.🔮 Predict: the adult irons for only one second. What happens? (a) it gets darker (b) the paper floats (c) writing turns green (d) writing stays faint
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) False (b) True
7. 7.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) an adult with an iron (c) a cotton bud (d) a small bowl
8. 8.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we change it (b) we keep it the same (c) we measure it
9. 9.True or false: writing the message is a job a child can do. (a) False (b) True
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is the one thing we change. (a) True (b) False
11. 11.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) an adult with an iron (c) a magnet (d) a cotton bud
13. 13.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) how dark the writing is (b) the ironing time (c) the kind of juice (d) the iron setting
14. 14.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we keep it the same (b) we measure it (c) we change it
15. 15.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) True (b) False
16. 16.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
17. 17.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) plugging in the iron (c) ironing the paper (d) putting the iron away
18. 18.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
19. 19.🍋 Secret message: who does this step — dipping the cotton bud? (a) an adult does it (b) a child can do it
20. 20.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) green (c) blue (d) brown
21. 21.True or false: a battery cell is needed for the secret lemon message. (a) False (b) True
22. 22.🧺 Which of these is not needed for the secret lemon message? (a) a battery cell (b) white paper (c) lemon juice (d) an adult with an iron
23. 23.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) an adult with an iron (c) a cotton bud (d) white paper
24. 24.⚖️ 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) False (b) True
25. 25.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) lemon juice (c) yeast (d) a mirror
26. 26.True or false: letting the paper dry is a job for an adult. (a) True (b) False
27. 27.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
28. 28.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) whoever is fastest (c) only an adult (d) any child
29. 29.🍋 Which of these steps is a job for an adult? (a) cutting the lemon (b) reading the message (c) letting the paper dry (d) dipping the cotton bud
30. 30.🔍 Which is the odd one out? (a) putting the iron away (b) reading the message (c) writing the message (d) letting the paper dry
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a magnet (b) a cotton bud (c) white paper (d) lemon juice
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same cotton bud (b) the iron setting (c) the same paper (d) the kind of juice
33. 33.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) no, it stays brown (d) yes, in the dark
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a balloon (c) lemon juice (d) white paper
35. 35.True or false: ironing the paper is a job for an adult. (a) False (b) True
36. 36.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
37. 37.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
38. 38.🧺 Do we need a small bowl for the secret lemon message? (a) needed (b) not needed
39. 39.🍋 Why does the lemon writing turn brown with heat? (a) the juice scorches first (b) paper turns lemony (c) heat adds colour (d) the iron is brown
40. 40.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True

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