Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 870 · 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: reading the message is a job for an adult. (a) False (b) True
2. 2.🍋 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
3. 3.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a cotton bud (c) white paper (d) turmeric powder
4. 4.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a small bowl (c) yeast (d) a mirror
5. 5.⚖️ 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 kind of juice (c) the ironing time (d) how dark the writing is
6. 6.True or false: putting the iron away is a job for an adult. (a) False (b) True
7. 7.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) False (b) True
8. 8.🍋 What colour does the lemon writing turn when an adult warms it? (a) brown (b) white (c) green (d) blue
9. 9.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) rub your eyes (b) wash your hands (c) skip washing (d) lick your fingers
10. 10.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) lemon juice (c) an adult with an iron (d) a magnet
11. 11.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) lemon juice (c) yeast (d) an adult with an iron
12. 12.🧺 Which of these is not needed for the secret lemon message? (a) white paper (b) an adult with an iron (c) lemon juice (d) turmeric powder
13. 13.⚖️ 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
14. 14.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
15. 15.🍋 Secret message: who does this step — ironing the paper? (a) a child can do it (b) an adult does it
16. 16.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is the one thing we change. (a) False (b) True
17. 17.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) letting the paper dry (c) plugging in the iron (d) cutting the lemon
18. 18.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
19. 19.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
20. 20.🔍 Which is the odd one out? (a) cutting the lemon (b) plugging in the iron (c) writing the message (d) putting the iron away
21. 21.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) whoever is fastest (c) only an adult (d) the youngest child
22. 22.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
23. 23.True or false: an adult with an iron is needed for the secret lemon message. (a) True (b) False
24. 24.🍋 Which of these steps is a job a child can do? (a) putting the iron away (b) writing the message (c) plugging in the iron (d) ironing the paper
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) an adult with an iron (c) a magnet (d) lemon juice
26. 26.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) a cotton bud (c) a balloon (d) turmeric powder
27. 27.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is the one thing we change. (a) False (b) True
28. 28.True or false: putting the iron away is a job a child can do. (a) False (b) True
29. 29.True or false: white paper is needed for the secret lemon message. (a) True (b) False
30. 30.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
31. 31.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a small bowl (b) a battery cell (c) a cotton bud (d) an adult with an iron
32. 32.🍋 Which of these steps is a job for an adult? (a) ironing the paper (b) dipping the cotton bud (c) writing the message (d) reading the message
33. 33.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is kept the same. (a) False (b) True
34. 34.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the iron setting (b) the ironing time (c) how dark the writing is (d) the same paper
35. 35.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, if shaken (c) yes, in the dark (d) no, it stays brown
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the kind of juice is what we measure. (a) False (b) True
37. 37.🍋 Secret message: who does this step — plugging in the iron? (a) an adult does it (b) a child can do it
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) white paper (c) an adult with an iron (d) a balloon
39. 39.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) plugging in the iron (d) writing the message
40. 40.True or false: ironing the paper is a job a child can do. (a) True (b) False

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