ingridscience

(Note: text marked with [] was omitted for primary students).

I’m going to talk about us - how we grew from a tiny dot. And about why do we all look different from each other. And why we all look like people, and not a cat or a tree.

(show image of DNA on overhead)
This stuff is the answer to all of these questions: DNA is the most amazing thing. You might have seen pictures of it before. There is DNA in every cell of our body - it is a spiral molecule. And it is the instructions to make our body. This is a billion times bigger than real DNA.

We all started as a tiny single cell. The DNA in that cell has instructions to tell the cell to [divide into more cells, and the instructions to tell those cells which to become back which to become front, then where to make a head, where to make a heart or an eye. Gradually, as more and more instructions are read, a human body] grows and develops into you.

(Show a petri dish of my DNA on overhead)
This is my DNA. I got from the cheek cells in my mouth. In that DNA is the instructions to make my body - my eye colour, my hair colour, why I need to wear glasses, even some of my personality. Your DNA looks the same on the outside, but when scientists look up close they see small differences between different peoples’ DNA. Those tiny differences are what make us all look different.
(Show image of DNA again and point out letters)

(Show hefty book of Shakespere)
If a book is the DNA instructions for a person, we need 100 of these books. Tiny parts of DNA are different between us, like spelling changes in words. That is why we look different. Most of our DNA instructions are the same, as we are all people, but those tiny changes are what makes us all look different.

A few of you have a change in your DNA that none of the rest of us have. Who here has red hair? I can show you exactly what change in the DNA makes your hair this colour - scientists have figured this out.
(Show sequence with one letter change in hair colour gene).
This is a part of a page in our book of DNA instructions. Can you find the one letter that is written in red? The rest of us have a G here. The redheads have a C here. This change in the instructions changes the colour of hair.

Theo has a change in his DNA that none of the rest of us has. Theo has a change to the instructions that tells the body how to grow. This change means that Theo is growing more slowly than the rest of us. Other people with the same DNA change as Theo also grow slowly and look like him. Only one in 10,000 people have the same DNA change as Theo.

Who has blue eyes? Another part of the DNA instruction book determines eye colour. You all have the same DNA letters in that part of the instructions and the rest of us have different instructions.

The only people that have the exact same DNA instructions are identical twins. Any identical twins here?

Everything about the way we look - our hair colour, how we develop, our eye colour, our height, also how we move, see, hear, eat, and talk is built from our DNA instructions. We are so complicated, that we can even think about ourselves thinking. It is absolutely mind boggling how complicated we are - and much of that complexity is built up from the instructions in our DNA. Life comes from this amazing molecule, DNA.

I've talked about our bodies and how we look like we do, but it's only part of the story. Now Theo's Dad will continue the story.

What about the bacteria in the starter mix?
It is a kind of bacteria that makes lactic acid from sugar. They eat sugar and make lactic acid.
Here are model molecules to show what happens. The bacteria eats the sugar and breaks it into this.
The acid made by the bacteria helps keep other bacteria and yeast away as they don’t like acid.
It also helps make more holes in the cake.

Lets do an activity to see what the lactic acid made by the bacteria does.
Put a scoop of baking soda in a cup.
One of the ingredients of the cake mixture was baking soda.
Pick up a cup of vinegar.
This is a acid like the acid made by the bacteria in the starter mixture.
Pick up your cup of baking soda, and a cup of vinegar. Keep them separate and take them back to your desk.
Once we are all sat down.... Just as in the cake recipe, with acid from the bacteria baking soda, pour the acid into the baking soda.
What happens (get bubbles).
The acid from the bacteria (which might make it smell as though the starter is off) and the baking soda we add to the recipe make gas bubbles. These get trapped in the batter and make the holes in the cake.

We will set up an activity to see what happens when yeast eats sugar.

Put a scoop of yeast and a scoop of sugar in at tube, then add warm water to half way up the tube.
Take a wooden stick and stir until the yeast and sugar have dissolved in the water. (What does that mean: solid to liquid).
Then put the tube in the tray on your desk.
We will leave the yeast for a while while we talk about what is happening in the tube.

The yeast is a living thing. It is dry or dormant in the jar, not doing anything. It can stay like that for a long time. When you add it to water and food it starts to eat.
The yeast eats the sugar you added to the tube. The yeast in the starter mixture of a yeast cake also eats sugar.

Yeast eats the sugar and breaks it down into carbon dioxide and ethanol.
(Show molecule models with older students.)
Ethanol is a kind of alcohol. For a bread recipe the ethanol does not stay around - it evaporates away. (When we make wine or beer with yeast, we keep the ethanol.)
Carbon dioxide - is it a gas, liquid or solid? It is a gas. We breathe it out. Yeast also breathes it out.
Your yeast should have activated by now and be making ethanol and carbon dioxide gas. What might the gas look like?

Hold your tube to the side and look for bubbles going up the side of the tube. Optional: use a flashlight to help find the bubbles. These are bubbles of carbon dioxide gas, made by the yeast as it eats the sugar you put in the tube. You might also see bubbles collecting at the top, making a kind of foam. Some of the tubes may even be spilling bubbles of gas over the top.
(If your parents make bread at home, you might have seen the same thing, in the bowl with the yeast and water at the beginning of the recipe.)

Optional: put a balloon over the tube, to collect the carbon dioxide gas and blow up the balloon.

1. The cat wanders the classroom, during discussion of topics below

CLASSIFICATION
She is a mammal: Gives birth to live babies. Feeds her babies her milk.
She is a carnivore.
Similarities and differences between Maggie and other animals (tigers, lions, other wild cats)

LIFE CYCLE
Maggie is an adult, 4.5 years old.
That is like a human being 34 years old
(1 human year is 15 cat years, 2 human years is 24 cat years, 3 human years is 28 cat years… plus 4 for each year).

BEHAVIOUR
Hissing and bushy tail = fighting
Purring = happy
Upright tail = friendly
Flicking tail and ears back = annoyed, stay away
Ears forward = interested

SURVIVAL
What does Maggie need for survival? She has it pretty good: food, water, shelter.
What about wild cats?

2. Students sit in a circle and take turns to either pet her or feed her a treat.

Students make a bridge out of paper clips/nails between two magnets.
What is the longest bridge you can make?
Does it help to have the paper clips/nails piled up or in single file?

Discussion:
See that magnetic force can pass through the paper clips.
Some metals can become magnets and attract another metal.

Before the class, prepare the iron filing container: sprinkle 1/4 teaspoon of iron filings into a larger salad container or 1/8 teaspoon into a small herb container. Apply a line of hot glue around the container edge and quickly seal shut. After a minute of cooling time, shake the iron filings around the sides of the container to locate any leaks, then seal these with more hot glue.

Each student experiments with moving magnets under the iron filings to see the patterns they make.
The shape of the magnetic field can be drawn with lines, that follow the lines that the iron filings make.

Discussion:
The patterns show how the force of the magnet spreads out around it.
Different magnets have different force field shapes.

For a lesson on the sun, this activity can be used to introduce how magnets have magnetic field lines around them.
The sun has very complex patterns of magnetic field lines, because of how the magnetic fields are formed within the sun:
Magnetic fields in the sun are made by the moving charged particles of the plasma particles which make up the sun. (Plasma is a fourth state of matter, more energetic than a gas, which exists in the very hot, high pressures of the sun).
The sun's plasma forms moving magnetic fields within the sun, which also loop outwards from it.
Show the field lines with this image: https://www.nasa.gov/sites/default/files/styles/full_width_feature/publ…
The immense magnetic fields of the sun pull loops of gas from the sun and out along the field lines.
Amazing movie at: https://sdo.gsfc.nasa.gov/assets/gallery/movies/Active_Regions_linkage_…
and even more amazing close ups at: https://www.nasa.gov/sites/default/files/styles/full_width_feature/publ… and https://www.nasa.gov/sites/default/files/styles/full_width_feature/publ…
Image of a prominence including the earth to scale: https://www.nasa.gov/sites/default/files/styles/full_width_feature/publ…
The Sun’s magnetic field lines sometimes twist so much that they “snap”, sprawling prominences (hot loops of plasma) into space. The plasma that does escape streams away from the sun as solar winds, filling the heliosphere which extends beyond the solar system.

Sunspots (darker regions on the surface of the Sun) are caused by strong magnetic fields blocking heat from the centre of the sun.
Larger sunspots are larger than earth.

Students catch fish, and figure out which ones won't be caught by the magnet.

Discussion:
The paper clip and staple fish mouths have iron in them, so are attracted to the magnet.
The aluminum is not attracted to magnets, so these fish cannot be caught.

Students record which materials are attracted to a magnet and which are not, and try to find any patterns in their observations.

Discussion:
Only some metals are attracted to magnets: iron (steel contains iron), nickel and cobalt.
With older students, maybe discuss how the electrons inside the atoms are aligned when something is magnetic.
Some rocks contain iron e.g. hematite so are attracted by magnets. Sometimes hematite can be magnetized so it becomes a magnet itself (called 'lodestone'.)

Stand the bike at the front of the class.

Ask students to find places on the bike where friction is increased or decreased to make the bike function.
Friction is high (brakes, pedal surfaces) where the rubbing surfaces are rough.
Friction is reduced (wheels, handle bars) with ball bearings and grease (rolling and lubricants).

Look at ball bearings taken apart to see how they work.
Look at pictures of other places that have ball bearings (handle bars, wheels, pedals).

See attachment for stand-alone version of this activity.