Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 733 · 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.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) True (b) False
2. 2.True or false: a mirror is needed for the secret lemon message. (a) True (b) False
3. 3.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
4. 4.🔍 Which is the odd one out? (a) reading the message (b) putting the iron away (c) cutting the lemon (d) ironing the paper
5. 5.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) reading the message (c) putting the iron away (d) ironing the paper
6. 6.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) yeast (c) a small bowl (d) an adult with an iron
7. 7.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
8. 8.⚖️ 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 kind of juice (c) the ironing time (d) how dark the writing is
9. 9.🧺 Do we need white paper for the secret lemon message? (a) not needed (b) needed
10. 10.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
11. 11.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing turns green (c) writing stays faint (d) it gets darker
12. 12.True or false: ironing the paper is a job a child can do. (a) False (b) True
13. 13.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
14. 14.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) cutting the lemon
15. 15.🧺 Which of these is needed for the secret lemon message? (a) a magnet (b) a mirror (c) lemon juice (d) turmeric powder
16. 16.True or false: a magnet is needed for the secret lemon message. (a) True (b) False
17. 17.🛟 Who should use the hot iron in the secret message experiment? (a) only an adult (b) the youngest child (c) any child (d) whoever is fastest
18. 18.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) a battery cell (d) an adult with an iron
19. 19.🔍 Which is the odd one out? (a) plugging in the iron (b) dipping the cotton bud (c) letting the paper dry (d) writing the message
20. 20.🔮 Can the brown writing go back to being invisible? (a) no, it stays brown (b) yes, if cooled (c) yes, in the dark (d) yes, if shaken
21. 21.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the iron setting (b) the kind of juice (c) the same paper (d) the ironing time
22. 22.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) white (d) green
23. 23.🧺 Do we need a magnet for the secret lemon message? (a) needed (b) not needed
24. 24.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) the ink is magnetic (c) it turned into air (d) the paper ate it
25. 25.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
26. 26.True or false: cutting the lemon is a job for an adult. (a) False (b) True
27. 27.True or false: lemon juice is not needed for the secret lemon message. (a) True (b) False
28. 28.⚖️ 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
29. 29.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) an adult with an iron (d) a magnet
30. 30.🧺 Do we need an adult with an iron for the secret lemon message? (a) not needed (b) needed
31. 31.🔍 Which is the odd one out? (a) cutting the lemon (b) dipping the cotton bud (c) putting the iron away (d) ironing the paper
32. 32.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the ironing time”? (a) we measure it (b) we change it (c) we keep it the same
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) a small bowl (c) lemon juice (d) a balloon
34. 34.🛟 Why must children keep their fingers away from the iron? (a) it is magnetic (b) it is cold (c) it is sticky (d) it can burn skin
35. 35.🔍 Which is the odd one out? (a) plugging in the iron (b) writing the message (c) ironing the paper (d) cutting the lemon
36. 36.⚖️ 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 measure it (c) we keep it the same
37. 37.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) wash your hands (c) rub your eyes (d) lick your fingers
38. 38.True or false: writing the message is a job for an adult. (a) True (b) False
39. 39.True or false: turmeric powder is needed for the secret lemon message. (a) True (b) False
40. 40.🧺 Which of these is needed for the secret lemon message? (a) a cotton bud (b) a balloon (c) turmeric powder (d) a magnet

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