Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 390 · 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 the one thing we change. (a) True (b) False
2. 2.⚖️ 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 same paper
3. 3.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the same cotton bud”? (a) we measure it (b) we keep it the same (c) we change it
4. 4.⚖️ 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
5. 5.🧺 Do we need lemon juice for the secret lemon message? (a) not needed (b) needed
6. 6.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is the one thing we change? (a) how dark the writing is (b) the same paper (c) the kind of juice (d) the ironing time
7. 7.🔍 Which is the odd one out? (a) letting the paper dry (b) cutting the lemon (c) plugging in the iron (d) putting the iron away
8. 8.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
9. 9.True or false: white paper is needed for the secret lemon message. (a) False (b) True
10. 10.⚖️ 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
11. 11.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) rub your eyes (c) skip washing (d) wash your hands
12. 12.🍋 Which of these steps is a job a child can do? (a) reading the message (b) cutting the lemon (c) plugging in the iron (d) ironing the paper
13. 13.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
14. 14.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
15. 15.True or false: putting the iron away is a job a child can do. (a) True (b) False
16. 16.🍋 Which of these steps is a job a child can do? (a) ironing the paper (b) putting the iron away (c) dipping the cotton bud (d) cutting the lemon
17. 17.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
18. 18.🧺 Which of these is not needed for the secret lemon message? (a) an adult with an iron (b) white paper (c) turmeric powder (d) a small bowl
19. 19.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) letting the paper dry (c) cutting the lemon (d) ironing the paper
20. 20.🔍 Which is the odd one out? (a) writing the message (b) ironing the paper (c) plugging in the iron (d) putting the iron away
21. 21.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
22. 22.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is what we measure? (a) the ironing time (b) the iron setting (c) the same paper (d) how dark the writing is
23. 23.🛟 Why must children keep their fingers away from the iron? (a) it is sticky (b) it can burn skin (c) it is magnetic (d) it is cold
24. 24.True or false: ironing the paper is a job a child can do. (a) True (b) False
25. 25.True or false: yeast is needed for the secret lemon message. (a) False (b) True
26. 26.🔮 Can the brown writing go back to being invisible? (a) yes, in the dark (b) yes, if cooled (c) yes, if shaken (d) no, it stays brown
27. 27.🧺 Do we need yeast for the secret lemon message? (a) not needed (b) needed
28. 28.⚖️ 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) True (b) False
29. 29.🍋 Which of these steps is a job a child can do? (a) cutting the lemon (b) ironing the paper (c) writing the message (d) putting the iron away
30. 30.📘 The browning of lemon juice with heat is a ___ change. (a) chemical (b) musical (c) physical (d) magnetic
31. 31.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
32. 32.🍋 Which of these steps is a job for an adult? (a) reading the message (b) writing the message (c) letting the paper dry (d) ironing the paper
33. 33.True or false: cutting the lemon is a job a child can do. (a) False (b) True
34. 34.⚖️ 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
35. 35.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) dark brown words (b) a rainbow (c) almost nothing (d) blue words
36. 36.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is what we measure. (a) True (b) False
37. 37.🍋 Secret message: who does this step — cutting the lemon? (a) a child can do it (b) an adult does it
38. 38.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) a small bowl (c) a cotton bud (d) a balloon
39. 39.🧺 Which of these is needed for the secret lemon message? (a) a balloon (b) a mirror (c) a cotton bud (d) yeast
40. 40.True or false: ironing the paper is a job for an adult. (a) False (b) True

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