Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 550 · 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: dipping the cotton bud is a job for an adult. (a) True (b) False
2. 2.⚖️ 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
3. 3.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
4. 4.🍋 Which of these steps is a job a child can do? (a) letting the paper dry (b) putting the iron away (c) ironing the paper (d) cutting the lemon
5. 5.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is sticky (c) it can burn skin (d) it is magnetic
6. 6.🍋 Secret message: who does this step — cutting the lemon? (a) an adult does it (b) a child can do it
7. 7.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) lick your fingers (d) skip washing
8. 8.True or false: writing the message is a job for an adult. (a) True (b) False
9. 9.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a battery cell (c) a small bowl (d) white paper
10. 10.⚖️ 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
11. 11.🛟 Who should use the hot iron in the secret message experiment? (a) the youngest child (b) only an adult (c) any child (d) whoever is fastest
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the same paper (b) the kind of juice (c) how dark the writing is (d) the same cotton bud
13. 13.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
14. 14.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
15. 15.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
16. 16.True or false: plugging in the iron is a job for an adult. (a) True (b) False
17. 17.🔍 Which is the odd one out? (a) putting the iron away (b) plugging in the iron (c) ironing the paper (d) letting the paper dry
18. 18.⚖️ 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 change it (c) we measure it
19. 19.🍋 Which of these steps is a job a child can do? (a) dipping the cotton bud (b) cutting the lemon (c) putting the iron away (d) plugging in the iron
20. 20.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
21. 21.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a small bowl (c) an adult with an iron (d) lemon juice
22. 22.🧺 Do we need turmeric powder for the secret lemon message? (a) not needed (b) needed
23. 23.True or false: lemon juice is needed for the secret lemon message. (a) False (b) True
24. 24.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
25. 25.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same paper”? (a) we keep it the same (b) we measure it (c) we change it
26. 26.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed
27. 27.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
28. 28.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) no, it stays brown (c) yes, if shaken (d) yes, if cooled
29. 29.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the iron setting is the one thing we change. (a) True (b) False
30. 30.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) writing the message (d) plugging in the iron
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is the one thing we change. (a) True (b) False
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) False (b) True
33. 33.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) blue words (b) dark brown words (c) almost nothing (d) a rainbow
34. 34.True or false: white paper is needed for the secret lemon message. (a) False (b) True
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a battery cell (c) an adult with an iron (d) a mirror
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the iron setting”? (a) we change it (b) we measure it (c) we keep it the same
37. 37.🍋 Which of these steps is a job for an adult? (a) plugging in the iron (b) writing the message (c) dipping the cotton bud (d) reading the message
38. 38.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a cotton bud (c) yeast (d) lemon juice
39. 39.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
40. 40.🍋 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

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