ingridscience

Before the lesson, cut open the heart, so that it can be done without time pressure. Cut it from the tip to the wide top, so that as many chambers of the heart as possible are cut open, and valves can be seen. Fold the halves of the heart back together before class.

What makes the blood push through the blood vessels? The heart. Where is your heart?
I have a real heart here. What animal do you think it is from?
Compare the size of the cow heart with ours (the size of our fist), and relative body sizes that each heart pumps blood through.

Students should touch the heart so that they know what real heart muscle feels like, and hold it to feel its weight.
Wash hands with soap afterwards.

Show features on the outside of the heart: the white fat, branching blood vessels on the surface that bring oxygen to the heart cells, and the large blood vessels protruding from the top of the heart. The tough, thick, white-walled vessels carry blood from the heart to the body (aorta) and lungs (pulmonary artery), and withstand enormous blood pressure. Other vessels bring blood back to the heart (these maybe absent).

Open the heart to view the internal features:
The left and right ventricles are the largest chambers at the bottom of the heart, with the walls of the left ventricle the thickest, as it pumps blood around the whole body. The smaller chambers at the top (the left and right atrium) are harder to find. They receive blood from the body.
Valves between each atrium and ventricle have long tendons holding them in place. Valves just inside the large blood vessels leaving the heart (semilunar valves) prevent blood from flowing back into the ventricles after each heartbeat.

Students can push their fingers through blood vessels and valves and follow the route of the blood into, through, and out of the heart:
From the lungs into the left atrium (vein gone), through the mitral valve (an AV valve) into left ventricle. Then through semilunar valve and the aorta to the whole body. Then back from the body through the (missing) vein into the right atrium, through tricuspid valve (other AV valve) into the right ventricle. Then through the other semilunar valve through the pulmonary artery to the lungs.

Show large left ventricle muscles, and large aorta leading from it. This chamber pumps blood around the whole body.

Relate valves closing to the heartbeat sound (lub-dub):
"Lub" is the AV valves (between atria and ventricles) closing and the rush of liquid behind them. "Dub" is the semilunar valves (between ventricle and artery) closing and the rush of liquid behind them.
Students can listen to their neighbour’s heart with an ear on the chest, or with a stethoscope.

Your pulse is a the push of blood along the blood vessels with each beat of the heart. Students can feel their pulse in several places, including the side of the neck or on their wrist.

See your blood:
Find places that you can see your own blood. Use some tools to help you find it: flashlight, mirror.
Wrist, under tongue, eyeballs the blood is easily visible. Shine a flashlight through closed fingers to see blood colour.
Blood is always red (not blue). When it is oxygenated it is bright red, and when it is depleted of oxygen it is darker red. Some veins look blueish green because of how light interacts with the skin over the veins.
Blood is red because iron (which carries the oxygen within the haemoglobin molecules in our red blood cells) turns red when it combines with oxygen (just like rusted iron is red because it is oxygenated). Some animals (lobsters, spiders and snails) have blue blood because they use copper instead of iron to carry oxygen, and copper is green-blue when oxygenated.

Find your pulse:
The blood moves through the blood vessels to bring oxygen to all parts of your body.
You can feel the blood moving in some places on your body - called a pulse. It is easier to feel where an artery presses against a bone.
Find your pulse in your wrist: gently press the first two fingers of one hand on the wrist just below the thumb of the other hand - this is the pulse in the radial artery, called the radial pulse. Also the ulnar pulse on the other side of the wrist in line with the pinky.
Find your pulse in your neck: place the first two fingers on the side of the neck under the jaw bone - this is the carotid pulse. (This is one of the strongest pulses as it is close to the heart. The carotid artery supplies blood to the brain. Only do one side at a time, so there is no danger of cutting off blood supply to the brain.)
Other pulses (see https://www.youtube.com/watch?v=qhgAEfLh1Ck to find them): temporal pulse (on the temples at the side of the head) and proximal brachial pulse (between the large muscles on the upper inner arm). Harder to find are behind the knee (popliteal artery), near the ankle joint (posterior tibial artery), and on the top of the foot (dorsalis pedis artery).

If you can cross your arms to feel the pulse in your wrist and neck simultaneously (set up one, then find the other), you may notice that the wrist pulse is just behind the neck pulse - you are feeling the wave of blood pressure moving away from your heart to the outer parts of your body.

Measure your pulse:
Each pulse is a push of blood from the heart. The heart beats your whole life.
Count how many pulses in 15 secs. (about 16, so 64 beats a minute, so about 30 thousand in a year, so 3 billion in a lifetime).
Go outdoors or to the gym and measure heart rate before exercise, and after. Try different kinds of exercise (jumping rope, lifting a two-pound weight, hula-hooping, walking) and measure heart rate immediately after. Your pulse will slow again after only 15 seconds.

Listen to your heartbeat:
Your heart makes a noise. Listen to your neighbour’s heart or use a stethoscope to hear your own.
The heart beat sound is from the rush of fluid behind closing valves: "Lub" is the AV valves (between atria and ventricles) closing and the rush of liquid behind them. "Dub" is the semilunar valves (between ventricles and arteries) closing and the rush of liquid behind them.

Refer to this animation of a beating heart:
Gif of beating human heart at https://en.wikipedia.org/wiki/Heart#/media/File:CG_Heart.gif
3D gif that you can rotate at https://sketchfab.com/3d-models/3d-animated-realistic-human-heart-v20-1…

Sand about 3cm of one end of the magnet wire, and sand about 3cm of the other end of the wire along one side only.
Wrap the wire around the tube to make a coil, leaving straight (sanded) ends uncoiled.
Slip the coil off the tube and wrap the ends around the coil to keep the coil wound.
Balance the coil between fingers, and spin it. If it wobbles when it spins, adjust to make it spin evenly.
This is going to be the coil of our motor. When we put electricity through it, it will become a magnet.
Tape paper clips to each terminal of the battery.
Slide the coil into the exposed loops of the paper clips.
Bring magnet close to the coil. It may start spinning on its own, or it may need a little flick to get it going - it might want to turn in either direction. Try holding the magnet under or beside the coil to find the best spot to keep it spinning. If the magnet is small enough, it can alternatively be stuck onto the magnet.

Simple explanation:
When electricity from the battery goes through the coil, it turns it into a magnet. The coil magnet is pushed or pulled by the permanent magnet held near to it, making the coil turn. This is a basic motor!

More advance explanation:
When electricity flows through a wire, it makes a magnetic field around it i.e. turns it into a tiny magnet. When the wire is coiled, the smaller magnetic fields of each wire combine to make a larger field i.e. one larger magnet (the wire must be insulated so that the electricity must to around and around the coil, not jump between wires).
The coil magnet is attracted or repelled by the permanent magnet that is brought near it, and so moves towards or away from it by spinning. (Whether it attracts or repels depends on which way the permanent magnet is held and which way the current is flowing through the wire.)
The coil is only sanded on one half of the wire on one side so that current only flow half the time, so the coil is only magnetic half the time. If the coil was magnetic all the time (by fully removing the insulation on both sides) it would be alternately attracted and repelled by the permanent magnet, so the coil would just oscillate, not spin.

Use the sandpaper to remove the plastic coating from about 2cm of each end of the wire (do this ahead of time for younger students). You will see the silvery-copper wire colour underneath.

Starting at the head of the nail, leave about 7cm wire sticking out, then wind the wire around it in tight turns. Move slowly down the nail, until all but the last 7cm is coiled - it will make about 80 turns. It does not matter if the coils lie on top of each other, though the tighter they are packed together the better.
Keep the coils pushed towards the head of the nail so that when winding is done, the pointed end of the nail is still exposed.
Secure the coil onto the nail with pieces of masking tape. (Skip the tape if galvanized nails are used, as the coils stay tight on the rough nail surface). Make sure that there is about 7cm straight wire sticking out at each end of the coil.

Fold over each end of the sandpapered wire ends so that the pointy end is tucked away. Fold a small piece of aluminum foil around the ends of the wire to cover the ends. The foil will help to make the connection between the copper wire and the battery.

Hold the foil-coated wire ends over the ends of the battery to make electricity flow through the coil, then touch the pointed tip of the electromagnet against smaller nails and paper clips.
Note that the battery becomes hot if it remains connected for a while so make sure it is disconnected frequently.
This activity drains batteries very fast (there is not much resistance in the wire).

Optional: set up stations that the students spend a few minutes each at:
nails large and small - the electromagnet will be able to pick up fewer larger nails than smaller ones
coins - coins that contain nickel (some pennies and nickels) will be picked up by the electromagnet
items with different kinds of metal - steel, containing iron, will be attracted to the electromagnet, whereas aluminum foil will not be e.g. use fish from magnetic fishing game
compass - bring the electromagnet near to a compass, to see it strongly attract the compass needle
See the attachment for cards to put at each station.

Students can also try linking their electromagnets together, to make an even stronger electromagnet.

How it works:
When there is electricity from the battery flowing through the copper wire, the coils make a magnetic field, which is significant with the many turns. This magnetic field turns the large nail into a magnet, strong enough to pick up small nails, paperclips etc.
Break the circuit by removing one wire from the battery. The nail is no longer magnetic and it drops the objects. (Sometimes a weak residual magetic field remains in the nail, so a few objects remain attached.)

NOTE that as there is little resistance in the wire, both the coiled wire and battery heat up if the battery is left connected for longer than half a minute. Using stations, with a short break between, makes sure that there is time for the wire to cool. In addition, switching out the batteries each time the students move means they don't heat up too much.
Using a longer wire will reduce how much the wire heats up.

For more detailed explanation see www.wonderhowto.com/how-to/make-simple-electromagnet-326803/

Uses of electromagnets: buzzers/door bells, speakers, cranes in metal recycling yards, maglev train. http://www.bbc.co.uk/schools/gcsebitesize/science/triple_aqa/keeping_th…

Please note that in a class of students it is likely that one of them is at least partially colourblind (1 in 12 males are colourblind). As this is an activity distinguishing colours, these students will not be able to tell some colours apart and perceive some colours differently, although the activity will be no less interesting for them. The common red/green colour blindness means reds and greens (or colours containing reds and greens such as browns) look similar. More information at colourblindawareness.org and colorblindguide.com/post/the-advantage-of-being-colorblind.

Prep:
Make a cardboard template of such a length so that when binder-clipped to the coffee stir stick it hangs to within 1cm of the bottom of the tub. Add a line across the template 2cm from the bottom. Add 1½ cm water to the tub.
Test the template and water level by cutting out a piece of filter paper the same size as the template, and drawing a marker line across, level with the line on the template. When clipped to the coffee stir stick the filter paper should just dip in the water, but the marker pen line does not. As the water creeps up the filter paper it draws up the colours of the marker.
Adjust the template if necessary, then make enough for the class.
Test out the markers available, to make sure that at least some of them are made up of two or more different colour inks.

Students use the template to cut out filter papers, add a marker line where indicated, as well as a dot of marker colour at the top of the filter paper strip (to remember what colour they started out with).
They can clip two or three filter paper strips to one stick, to run several chromatograms at a time, but should make sure that the filter papers do not touch each other or the sides of the tub.
Make sure they remove the strip from the water before the colours run into their coloured dot at the top, and lay it on a paper towel to dry.

Black, brown, blue, green colours usually work well. The darker colours are generally a mixture of more colours.
From a pack of marker pens, students can document what colour inks are in each pen, then figure out how many inks are used to make up a full pack of pens. They can record their results either on their own worksheet (attached), or better on a class table (see photos) that accumulates data as they all add to it.
Look at the data as a class, and question 'which marker pens are made of only one dye', which are made of many dyes' etc (see photo for discussion questions).

Extend with the activity Chromatography with the ink pens (black) for a forensics use of the method to identify the black pen that wrote a note.

By choosing the best colours to make chromatograms with, making wider sheets of filter paper to run multiple colours at once, then cutting and mounting the best patterns, some great art collages emerge (see photos).

The chemistry:
Chromatography is used for separating mixtures of molecules in a solution. This technique is used a lot by chemists and forensic scientists.
How does chromatography work?
The coloured dye molecules in the ink of the pen are attracted to both the water that it is in, but also the surface of the filter paper. Each different colour is attracted to the water or the filter paper to different extents. As the water moves up, the dye molecules that are most attracted to the water will move along fast with it. If the dye molecules are mostly attracted to the paper, they will get stuck to the paper and not move along with the water at all. Most colours are attracted to both the water and the paper, so will travel with the water for a while, then stick to the paper for a while. Depending on the relative attraction of a dye to the water and the paper, a colour will travel at its own rate. The differing rates of travel separate out the colours.

Hand out a “moon” to each student, and ask them to stand in a large circle around the bulb, with two arm length’s space between each student if possible. Tell them that their head is the “earth”, and they will be viewing their moon from earth.
Ask the students how the moon moves around the earth - they can mimic the movement by moving their model moon around them, turning their body with it so they can see the moon at all times. The real moon rotates around the earth once each month.
Darken the room so that the only light source is the bare light bulb in the centre of the room - the “sun”.
Ask students to turn their backs to the sun and hold their moon at arms length away from them. The moon should appear fully lit as the sun’s light reflects from it. (Make sure the earth (their head) does not make a shadow on the moon.) When the real moon is in this position, on the far side of the earth from the sun, we see a “full moon”.
Now ask students to turn and face the sun and hold their moons in front of them at arms length, towards the sun but not covering its light. They should see the sun, and the dark side of their moon. When the real moon is positioned between the earth and the sun, the side facing us in in shadow and not visible - it is called a “new moon”.
From this position, ask the students to slowly move their moon to their left. As they do so, they should see a bright crescent appearing on the side of their moon as they start to see the sun’s light reflected from it. The real moon in this position relative to the earth and sun is called a “crescent moon”.
As they continue to move their moon around them to the left (turning their body with it), the crescent will become wider until half of the moon is illuminated - a “half moon”.
Continuing to turn, they pass through the full moon, another half moon, another crescent moon (curved in the other direction this time) and finally the new moon again.
The entire rotation of the real moon around the earth takes a month, and during that month the moon passes through these same phases.
The students should be given time to experiment with their model, so that they can fully understand how the sun’s reflected light makes the shape of each phase.

If the earth’s shadow falls on the moon, a lunar eclipse occurs. This is modelled by facing away from the sun and blocking the sun's light falling on the moon with your head.
If the moon blocks the sunlight reaching earth, a solar eclipse occurs. This is modelled by facing the sun and using the moon to block the sun's light reaching earth.

Go outside to look at the real phases of the moon (when the moon is out on a non-cloudy day).
Montage of Moon phases from NASA: https://solarsystem.nasa.gov/resources/676/phases-of-the-moon/ and https://spaceplace.nasa.gov/oreo-moon/en/Moon_phases_all_L.en.jpg
Interactive showing the phases of the moon, and the Moon phase today, from NASA: https://solarsystem.nasa.gov/moons/earths-moon/lunar-phases-and-eclipse…