Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 306 · 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) the juice scorches first (c) heat adds colour (d) paper turns lemony
2. 2.🍋 Which of these steps is a job for an adult? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) ironing the paper
3. 3.🔍 Which is the odd one out? (a) putting the iron away (b) ironing the paper (c) cutting the lemon (d) writing the message
4. 4.🍋 Which of these steps is a job for an adult? (a) dipping the cotton bud (b) reading the message (c) letting the paper dry (d) plugging in the iron
5. 5.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) skip washing (b) lick your fingers (c) wash your hands (d) rub your eyes
6. 6.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) cutting the lemon (c) putting the iron away (d) reading the message
7. 7.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
8. 8.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) yes, in the dark (c) no, it stays brown (d) yes, if shaken
9. 9.🍋 Secret message: who does this step — dipping the cotton bud? (a) a child can do it (b) an adult does it
10. 10.🍋 Which of these steps is a job for an adult? (a) reading the message (b) cutting the lemon (c) writing the message (d) dipping the cotton bud
11. 11.🍋 Secret message: who does this step — reading the message? (a) a child can do it (b) an adult does it
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is what we measure. (a) False (b) True
13. 13.True or false: dipping the cotton bud is a job for an adult. (a) False (b) True
14. 14.True or false: dipping the cotton bud is a job a child can do. (a) False (b) True
15. 15.🧺 Do we need turmeric powder for the secret lemon message? (a) needed (b) not needed
16. 16.🧺 Do we need a cotton bud for the secret lemon message? (a) not needed (b) needed
17. 17.🧺 Which of these is needed for the secret lemon message? (a) turmeric powder (b) white paper (c) yeast (d) a mirror
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 measure it (c) we change it
19. 19.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) the kind of juice (b) how dark the writing is (c) the same cotton bud (d) the ironing time
20. 20.🧺 Which of these is not needed for the secret lemon message? (a) a balloon (b) a cotton bud (c) white paper (d) a small bowl
21. 21.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
22. 22.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a balloon (c) a cotton bud (d) a mirror
23. 23.🔍 Which is the odd one out? (a) plugging in the iron (b) reading the message (c) cutting the lemon (d) ironing the paper
24. 24.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
25. 25.🧺 Which of these is not needed for the secret lemon message? (a) a small bowl (b) a mirror (c) lemon juice (d) white paper
26. 26.⚖️ 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
27. 27.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) lemon juice (c) a small bowl (d) a cotton bud
28. 28.🧺 Do we need white paper for the secret lemon message? (a) needed (b) not needed
29. 29.🍋 Secret message: who does this step — letting the paper dry? (a) a child can do it (b) an adult does it
30. 30.🍋 Why can’t you see the lemon writing once it dries? (a) dry juice is see-through (b) it turned into air (c) the paper ate it (d) the ink is magnetic
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “how dark the writing is”? (a) we measure it (b) we change it (c) we keep it the same
32. 32.True or false: ironing the paper is a job for an adult. (a) True (b) False
33. 33.True or false: reading the message is a job for an adult. (a) True (b) False
34. 34.🧺 Do we need a battery cell for the secret lemon message? (a) needed (b) not needed
35. 35.True or false: a mirror is needed for the secret lemon message. (a) False (b) True
36. 36.🍋 Which of these steps is a job for an adult? (a) putting the iron away (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
37. 37.⚖️ 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) True (b) False
38. 38.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same paper is kept the same. (a) False (b) True
39. 39.🍋 What colour does the lemon writing turn when an adult warms it? (a) blue (b) brown (c) green (d) white
40. 40.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) the kind of juice (b) how dark the writing is (c) the iron setting

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