Over the next two weeks, activities will use frozen carbon dioxide – better known as ‘dry ice’. This material can be purchased through some party supply companies or direct from BOC Gases or Air Liquide.
Warning: Dry ice is not like water ice. Do not allow it to touch your skin; the extreme cold can cause harm. Wear thick gloves and safety goggles when doing this activity.
What’s happening?
At room temperature and ‘normal’ pressure (1 atmosphere), carbon dioxide (CO2) is a gas. Pouring water over the dry ice made it quickly turn from a solid into a gas without passing through a liquid phase. The dry ice itself is so cold the cold CO2 gas it releases chills the water in the air, turning it into a foggy vapour.
What’s happening?
As you’re sitting quietly, reading Science by Email, it’s unlikely that you’ll be taking in deeps breaths. While your breathing is influenced by a range of factors, the average person will inhale and exhale anywhere between 12 and 20 times per minute, and will come nowhere near filling their lungs completely.
What’s happening?
Your veins have a rather nifty way of stopping blood from flowing back the wrong way – small flaps called ‘valves’ maintain a direction of blood-flow through your body. Some electronics also need to ensure the current only ever flows in a single direction. To do this, they use a component called a diode that acts a bit like an electrical valve.
What’s happening?
Combination locks like these ones require a code with a string of digits that look something like ’3 – 16 – 7’. To unlock, the dial needs to be turned clockwise all the way around at least twice until the dial is pointing straight up (at the ‘twelve o’clock’ position). This ensures the tumblers are lined up correctly.
The first turn takes the dial from the starting position to point at number 2. It pushes the back tumbler so its gap (our black line) lines up with a release mechanism, or the latch. The second turn goes back the other way – anticlockwise – five places. This pushes the middle tumbler so its gap lines up as well. The third turn goes clockwise again by four places, rotating the front tumbler so all three gaps are together. This forms a space for the release mechanism to lift into, allowing you to lift the latch and open the lock.
What’s happening?
Before Isaac Newton, nobody gave too much thought to what made us fall back to Earth after we jump, or why we can’t float into the sky. This 17th century English philosopher had an interesting thought – he wondered if it had something to do with the reason planets stayed in orbits around the Sun. He came up with some rules about gravity and forces, explaining how all things moved.
What’s happening?
At first, waves seem like fairly simple things to understand. Go to the beach, and you’ll see plenty of them. A flag can wave in the wind, your hand can wave goodbye and even the air can ripple in waves, producing sound. But not all waves are the same. How does light move as a wave? Is a wave at the beach the same as a sound wave?
This simple wave machine demonstrates how energy can move through something and form a pattern of movements. Each skewer is joined to the next by a section of tape; by pushing down one end of a skewer, you twist the tape. It springs back again, pulling the skewer back so it shoots up, now twisting the tape in the opposite direction. Meanwhile, the tape is also tugging on the next skewer, making it wobble. Energy transfers down the tape, making each skewer see-saw up and down, creating a wave.
If you were to take all of the stuff that makes up our solar system, 99.86 per cent of it would be from the Sun, and consist of mostly hydrogen and helium. It’s not only a big object (109 planet Earths sitting side-by-side could fit across its diameter), its mass gives it a lot of gravity to squeeze all of that hydrogen and helium together.
All of that squeezing makes the Sun’s particles bump into one another rather energetically. In fact, the particles are pushed together so tightly, the forces that help hydrogen atoms stick together can reach out to one another and grab onto other atoms, making even bigger atoms. This is called nuclear fusion and is how hydrogen can turn into the slightly bigger element, helium.
Water and oil aren’t exactly the best of friends. Because of their shape and the way their atoms stick together, they prefer keeping to themselves rather than mixing with one another. The Greek root for water is ‘hydro’, so we say that water is ‘hydrophilic’ (loves water) while oil is ‘hydrophobic’ (afraid of water). Because a drop of water has more mass than the same sized drop of oil, gravity pulls on it with more force, pulling it to the bottom.
Make an ice core in your freezer that you can carefully study later (that means eat). An ice core is like a time machine into the past. Some ice in the Artic, Antarctica and in glaciers has been frozen for hundreds and thousands of years and can tell scientists what the climate was like all those years ago. The ash and gas of volcanoes can also be found trapped in the ice, telling us the size of past eruptions and when they occurred.
You are watching fluid dynamics in motion. Fluid dynamics is the science of moving fluids. A fluid is something that flows and takes the shape of its container. Liquids like water, shampoo and volcanic lava are fluids. Even gases are fluids, although we can’t always see them flowing about.
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