Invisible Ink Experiment Worksheet

Science experiments lesson 13: Lemon juice invisible ink · Set 674 · 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.True or false: turmeric powder is not needed for the secret lemon message. (a) False (b) True
2. 2.🔮 Can the brown writing go back to being invisible? (a) yes, if cooled (b) no, it stays brown (c) yes, in the dark (d) yes, if shaken
3. 3.🛟 Lemon juice stings cuts and eyes. What should you do after the experiment? (a) wash your hands (b) rub your eyes (c) skip washing (d) lick your fingers
4. 4.⚖️ 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 same paper (c) how dark the writing is (d) the same cotton bud
5. 5.⚖️ Fair test — does lemon juice or orange juice make darker secret writing? What do we do with “the kind of juice”? (a) we change it (b) we keep it the same (c) we measure it
6. 6.🛟 Who should use the hot iron in the secret message experiment? (a) any child (b) the youngest child (c) whoever is fastest (d) only an adult
7. 7.True or false: white paper is not needed for the secret lemon message. (a) False (b) True
8. 8.🍋 Which of these steps is a job for an adult? (a) reading the message (b) dipping the cotton bud (c) letting the paper dry (d) cutting the lemon
9. 9.⚖️ 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
10. 10.True or false: a cotton bud is needed for the secret lemon message. (a) True (b) False
11. 11.🍋 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) plugging in the iron
12. 12.🔍 Which is the odd one out? (a) dipping the cotton bud (b) letting the paper dry (c) putting the iron away (d) reading the message
13. 13.True or false: plugging in the iron is a job for an adult. (a) False (b) True
14. 14.⚖️ 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 iron setting (c) the kind of juice
15. 15.🧺 Do we need lemon juice for the secret lemon message? (a) needed (b) not needed
16. 16.⚖️ 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
17. 17.🍋 Secret message: who does this step — writing the message? (a) an adult does it (b) a child can do it
18. 18.🧺 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 balloon
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 ironing time (b) the same paper (c) the kind of juice (d) the same cotton bud
20. 20.⚖️ 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
21. 21.📘 The browning of lemon juice with heat is a ___ change. (a) physical (b) magnetic (c) musical (d) chemical
22. 22.🧺 Do we need a battery cell for the secret lemon message? (a) not needed (b) needed
23. 23.⚖️ 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 ironing time (c) the kind of juice
24. 24.🔍 Which is the odd one out? (a) ironing the paper (b) letting the paper dry (c) writing the message (d) dipping the cotton bud
25. 25.🍋 Secret message: who does this step — putting the iron away? (a) a child can do it (b) an adult does it
26. 26.🧺 Which of these is not needed for the secret lemon message? (a) a mirror (b) lemon juice (c) a small bowl (d) an adult with an iron
27. 27.🍋 Why does the lemon writing turn brown with heat? (a) paper turns lemony (b) heat adds colour (c) the juice scorches first (d) the iron is brown
28. 28.🧺 Three of these are needed for the secret lemon message. Which one is NOT needed? (a) a battery cell (b) an adult with an iron (c) lemon juice (d) white paper
29. 29.🔍 Which is the odd one out? (a) ironing the paper (b) putting the iron away (c) cutting the lemon (d) dipping the cotton bud
30. 30.🍋 Secret message: who does this step — letting the paper dry? (a) an adult does it (b) a child can do it
31. 31.🍋 Secret message: who does this step — reading the message? (a) an adult does it (b) a child can do it
32. 32.True or false: plugging in the iron is a job a child can do. (a) True (b) False
33. 33.True or false: letting the paper dry is a job a child can do. (a) True (b) False
34. 34.🔮 Predict: the adult irons for only one second. What happens? (a) the paper floats (b) writing stays faint (c) it gets darker (d) writing turns green
35. 35.🧺 Which of these is needed for the secret lemon message? (a) a mirror (b) yeast (c) a battery cell (d) a cotton bud
36. 36.🍋 What colour does the lemon writing turn when an adult warms it? (a) green (b) white (c) brown (d) blue
37. 37.True or false: white paper is needed for the secret lemon message. (a) False (b) True
38. 38.🍋 Which of these steps is a job for an adult? (a) writing the message (b) letting the paper dry (c) putting the iron away (d) reading the message
39. 39.True or false: a small bowl is not needed for the secret lemon message. (a) False (b) True
40. 40.🧺 Do we need a balloon for the secret lemon message? (a) not needed (b) needed

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