Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 695 · 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? What do we do with “the kind of juice”? (a) we measure it (b) we keep it the same (c) we change it
2. 2.🧺 Which of these is needed for the secret lemon message? (a) a battery cell (b) a cotton bud (c) yeast (d) a balloon
3. 3.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) chemical (c) musical (d) magnetic
4. 4.🔍 Which is the odd one out? (a) letting the paper dry (b) reading the message (c) dipping the cotton bud (d) plugging in the iron
5. 5.True or false: cutting the lemon is a job a child can do. (a) False (b) True
6. 6.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
7. 7.🧺 Which of these is not needed for the secret lemon message? (a) a cotton bud (b) lemon juice (c) a small bowl (d) a balloon
8. 8.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
9. 9.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) an adult with an iron (c) a small bowl (d) a magnet
10. 10.🍋 Which of these steps is a job a child can do? (a) plugging in the iron (b) writing the message (c) cutting the lemon (d) putting the iron away
11. 11.True or false: writing the message is a job for an adult. (a) False (b) True
12. 12.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the same cotton bud is what we measure. (a) False (b) True
13. 13.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) an adult with an iron (b) a small bowl (c) white paper (d) a mirror
14. 14.⚖️ 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 change it (c) we keep it the same
15. 15.🧺 Which of these is not needed for the secret lemon message? (a) lemon juice (b) a cotton bud (c) a small bowl (d) yeast
16. 16.⚖️ 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) how dark the writing is (c) the iron setting (d) the kind of juice
17. 17.🔍 Which is the odd one out? (a) dipping the cotton bud (b) ironing the paper (c) writing the message (d) reading the message
18. 18.🔮 Predict: you write with plain water instead of lemon juice. What appears after ironing? (a) almost nothing (b) dark brown words (c) a rainbow (d) blue words
19. 19.🍋 What colour does the lemon writing turn when an adult warms it? (a) white (b) blue (c) brown (d) green
20. 20.🍋 Secret message: who does this step — plugging in the iron? (a) a child can do it (b) an adult does it
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) True (b) False
22. 22.🛟 Why must children keep their fingers away from the iron? (a) it is cold (b) it is magnetic (c) it is sticky (d) it can burn skin
23. 23.True or false: putting the iron away is a job a child can do. (a) False (b) True
24. 24.🍋 Why can’t you see the lemon writing once it dries? (a) the paper ate it (b) the ink is magnetic (c) dry juice is see-through (d) it turned into air
25. 25.True or false: plugging in the iron is a job for an adult. (a) False (b) True
26. 26.🧺 Do we need a magnet for the secret lemon message? (a) not needed (b) needed
27. 27.True or false: yeast is needed for the secret lemon message. (a) True (b) False
28. 28.🔍 Which is the odd one out? (a) cutting the lemon (b) letting the paper dry (c) dipping the cotton bud (d) writing the message
29. 29.True or false: a balloon is not needed for the secret lemon message. (a) False (b) True
30. 30.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: how dark the writing is is kept the same. (a) True (b) False
31. 31.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? Which of these is kept the same? (a) how dark the writing is (b) the kind of juice (c) the same paper
32. 32.True or false: ironing the paper is a job a child can do. (a) False (b) True
33. 33.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a cotton bud (b) yeast (c) an adult with an iron (d) white paper
34. 34.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) lemon juice (b) turmeric powder (c) white paper (d) a cotton bud
35. 35.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
36. 36.⚖️ 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
37. 37.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? True or false: the ironing time is what we measure. (a) False (b) True
38. 38.⚖️ 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
39. 39.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) lick your fingers (b) skip washing (c) rub your eyes (d) wash your hands
40. 40.⚖️ 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

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