Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 817 · 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.🍋 Why does the lemon writing turn brown with heat? (a) the iron is brown (b) heat adds colour (c) the juice scorches first (d) paper turns lemony
2. 2.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) an adult with an iron (c) yeast (d) turmeric powder
3. 3.⚖️ 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
4. 4.🔍 Which is the odd one out? (a) letting the paper dry (b) writing the message (c) putting the iron away (d) reading the message
5. 5.True or false: reading the message is a job for an adult. (a) False (b) True
6. 6.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
7. 7.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) putting the iron away (c) plugging in the iron (d) reading the message
8. 8.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it can burn skin (d) it is sticky
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) a small bowl (c) white paper (d) an adult with an iron
10. 10.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the ironing time (b) the iron setting (c) the kind of juice (d) how dark the writing is
11. 11.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
12. 12.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) plugging in the iron (d) dipping the cotton bud
13. 13.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a magnet (c) white paper (d) a mirror
14. 14.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
15. 15.⚖️ 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
16. 16.True or false: a mirror is not needed for the secret lemon message. (a) True (b) False
17. 17.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a mirror (c) white paper (d) a small bowl
18. 18.🛟 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
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is kept the same. (a) False (b) True
20. 20.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) white paper (b) turmeric powder (c) a small bowl (d) lemon juice
21. 21.⚖️ 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
22. 22.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a magnet (c) lemon juice (d) a small bowl
23. 23.True or false: letting the paper dry is a job a child can do. (a) False (b) True
24. 24.⚖️ 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 change it (c) we measure it
25. 25.🍋 Which of these steps is a job for an adult? (a) reading the message (b) letting the paper dry (c) dipping the cotton bud (d) cutting the lemon
26. 26.True or false: yeast is not needed for the secret lemon message. (a) True (b) False
27. 27.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) letting the paper dry (d) plugging in the iron
28. 28.🛟 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
29. 29.🧺 Do we need a small bowl for the secret lemon message? (a) not needed (b) needed
30. 30.🔍 Which is the odd one out? (a) dipping the cotton bud (b) writing the message (c) plugging in the iron (d) letting the paper dry
31. 31.🔮 Predict: the adult irons for only one second. What happens? (a) writing turns green (b) writing stays faint (c) the paper floats (d) it gets darker
32. 32.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
33. 33.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) a small bowl (c) a cotton bud (d) a balloon
34. 34.⚖️ 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
35. 35.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the kind of juice (b) the ironing time (c) the same cotton bud (d) how dark the writing is
36. 36.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
37. 37.True or false: plugging in the iron is a job for an adult. (a) True (b) False
38. 38.True or false: dipping the cotton bud is a job a child can do. (a) True (b) False
39. 39.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
40. 40.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) writing the message (d) plugging in the iron

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