Watchly Safety Review

SCIENCE CLASS #4- How to Waterproof Your Hand

Mark Rober

27:40 · 1.1M views · March 30, 2020

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Minor FlagsReviewed June 2026

2Minor Flags

4No Issues

This science lesson from Mark Rober is genuinely excellent educational content that makes physics concepts like surface tension, cohesion, and adhesion fun and accessible for kids. The video is clean, enthusiastic, and packed with hands-on demos kids can replicate at home, with no meaningful content concerns beyond a brief mention of water striders 'sucking guts out' of prey and some mild engagement prompts for social media challenges.

Content Breakdown · 6 Categories

Strong & Crude LanguageNot present

No profanity, slurs, or crude language appears in this science education video; the closest instance is a mild 'heck yeah' used enthusiastically.

See evidence (2)

“'heck yeah that Pointer's a Hot Wheels track'”

“'what the heck does cohesion mean'”

Realistic Violence, Threats & WeaponsNot present

No realistic violence, threats, or weapons appear in this video; the only mention of anything remotely aggressive is a figurative phrase about 'punching coronavirus in the face,' which is clearly metaphorical.

See evidence (1)

“'what can you do to punch coronavirus in the face' — clearly a metaphor for fighting the pandemic”

Hidden Advertising & Sponsored ContentA little

Bose headphones are mentioned as a prize giveaway for challenge participants, but this is disclosed openly and transparently rather than hidden; no undisclosed commercial promotion is present.

See evidence (1)

“'Bose wanted to give out like eight pairs of headphones so these a700s which are kind of dope they will be reaching out to you'”

Parasocial & Emotional ManipulationNot present

The host uses warm, encouraging language typical of an educational creator but does not guilt-trip viewers or manufacture emotional dependence; phrases like 'you guys are the best' are standard and not manipulative in context.

See evidence (1)

“'you guys are the best this is crazy we'll see you next time'”

Engagement Baiting & Manipulative CTAsA little

The host asks viewers to tag him on social media and participate in a challenge, but these are straightforward educational CTAs without guilt-tripping, superstition hooks, or coercive 'true fan' language.

See evidence (2)

“'tag me on any social media with your responses'”

“'you could just post about this class to your friends on social media and they'll pick someone'”

Playful & Fantasy ViolenceNot present

No playful or fantasy violence appears in this video; the only tangentially relevant content is a brief mention that water striders 'suck the guts out' of prey insects, which is a factual natural history observation rather than stylized violence.

See evidence (1)

“'they'll find animals that can't swim in the water coming down the stream and then they just like suck their guts out' — factual description of water strider predation”

What Parents Need to Know

Parents can feel confident letting kids of almost any school age watch this video. Mark Rober, a former NASA engineer, teaches real physics concepts — surface tension, cohesion, adhesion, and hydrophobic coatings — using simple household materials like paper clips, soap, baby powder, and food coloring. The lesson was filmed during COVID-19 lockdowns and includes a brief, age-appropriate mention of how soap destroys the coronavirus's fatty shell, which is accurate and reassuring rather than scary. There's a passing comment about water striders eating prey by 'sucking their guts out,' which is factually accurate but mildly graphic for very young children. The video encourages kids to try experiments at home and share results on social media, which parents may want to supervise. A Bose headphone giveaway is mentioned as a prize for a challenge, which is light sponsored content but not pushy or deceptive.

Talk to Your Kids About

1Why do you think soap is so good at cleaning your hands? What does it do to the water and to germs?
2Can you think of other places in nature where water sticking to surfaces (adhesion) or to itself (cohesion) might be important?
3Mark said he wants to build a 'mental model' instead of just memorizing facts — what do you think that means, and why might it be more useful?
4If you tried the penny water drop experiment at home, how many drops do you think you could fit? What would happen if you added a tiny drop of soap?

SCIENCE CLASS #4- How to Waterproof Your Hand

Protected Viewing

What's This Video About?

Lots of juicy demos relating to surface tension! NO CLASS THIS WEDS!! I'm filming one of my normal monthly videos that day. Back on Friday though!! Go check out Dianna's awesome channel- https://youtu.be/8aaXZDazPxs CHALLENGE- float as many paper clips as you can and then come up with a creative way to ruin the surface tension and have them all sink. Tag me on any social media with your responses. Question for next time- How do astronauts weigh themselves when they are floating and weightless.

Frequently Asked Questions

What age is this video appropriate for?

This video is suitable for children around age 7 and up. The science concepts are explained clearly with visual demos, and there is no inappropriate content — though very young children may find the abstract physics less engaging.

Is there anything scary or disturbing in this video?

There is one brief mention that water strider insects find prey and 'suck their guts out,' which is biologically accurate but mildly graphic. It's presented matter-of-factly and is unlikely to upset most school-age children, but very sensitive younger kids might find it off-putting.

Is this video actually educational, or is it just entertainment?

It is genuinely educational. Mark Rober covers real physics concepts — surface tension, molecular cohesion, adhesion, hydrophobic surfaces, and capillary action — using accurate science and clear visual demonstrations that align well with school curricula.

Are there any ads or sponsored segments in this video?

A Bose headphone giveaway is briefly mentioned as a prize for a viewer challenge, which counts as light brand involvement. It is not a dedicated ad segment and does not dominate the content, but parents should be aware it exists.

Can kids try the experiments shown at home?

Yes — Mark specifically encourages home experiments using common household items like paper clips, a bowl of water, dish soap, baby powder, food coloring, and whole milk. These are all safe, low-mess activities appropriate for kids with basic adult supervision.

Does the video mention COVID-19, and is it handled appropriately?

Yes, the video was filmed during the early COVID-19 pandemic and briefly explains how soap destroys the virus's fatty outer shell. The explanation is scientifically accurate, calm, and reassuring, and is unlikely to cause anxiety in children.