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Chemistry of baking yeast cake

Summary
Experiments with yeast, then baking soda and vinegar show how gas is made while bread is made with a starter, and how they make the holes in the cake.
Curriculum connection (2005 science topic)
Physical Science: Chemistry (grade 7)
Procedure

What is in the starter mix that we used for making sourdough bread or traditional bread/yeast cake?
Today we will investigate the living things that are in here, and what they do.

What living things could be in there? They must be small...
Living things in this starter are yeast and bacteria.
(There are some kinds of yeast and bacteria that make you sick, but there are plenty that are helpful to us, and these ones are helpful yeast and bacteria).
The yeast and bacteria in here live well together, and stop other yeasts or bacteria from growing.

Activity to determine the role of the yeast in the starter mixture.

Activity to determine the role of the bacteria in the starter mixture.

The starter has a yeast and a Lactobacillus bacteria in it.

Notes

A little much information for grade 2/3 class. Suggest either missing out the molecule models explaining what is going on (the yeast starts bubbling rapidly, so don't need much time waiting for it). Or just do one of the activities.

Grades taught
Gr 2
Gr 3

Yeast eats sugar and makes gas

Summary
Students observe yeast making carbon dioxide as it metabolizes (eats and breaks down) sugar.
Science topic (2005 curriculum connection)
Life Science: Animal Growth and Changes (grade 2)
Life Science: Plant Growth and Changes (grade 3)
Physical Science: Chemistry (grade 7)
Materials
  • Tall thin tubes e.g. 15ml tubes
  • Scoops (1/8 teaspoon)
  • Yeast
  • Sugar
  • Water (very warm to touch) in dropper bottles
  • Kettle to boil water, or tap with very hot water
  • Stir stick
  • Tube racks
  • Waste for stir stick
  • optional: flashlight to help visualize
  • Sugar molecule model
  • Piece of bread/yeast cake (or look at bread that students make)
Procedure

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.

Attached documents
bread_booklet.pdf
bread_and_cakes_take_home.pdf
Notes

Yeast is a fungus.

Grades taught
Gr K
Gr 1
Gr 2
Gr 3
Gr 4
Gr 5
Gr 6
Gr 7

Pet cat demonstration

Summary
Pet cat wanders the classroom, while class discusses what kind of animal she is, her adaptations and survival.
Science topic (2005 curriculum connection)
Life Science: Characteristics of Living Things (grade K)
Life Science: Needs of Living Things (grade 1)
Life Science: Animal Growth and Changes (grade 2)
Materials
  • Pet cat comfortable with people
  • Classroom that can be secured closed
  • Pet treats
    Procedure

    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.

    Grades taught
    Gr 1
    Gr 2

    Magnets: paper clip bridge

    Summary
    Students make a bridge of paper clips between two magnets. The materials can be used as a free experimentation activity.
    Science topic (2005 curriculum connection)
    Physical Science: Force and Motion (grade 1)
    Materials
    • Two magnets per student
    • 20 or so paper clips per student, or better small nails (which can't be hooked together)
    Procedure

    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.

    Grades taught
    Gr 1
    Gr 2

    Magnetic force field patterns

    Summary
    Students use iron filings to visualize the direction of the magnetic field lines and the shape of magnetic fields around various magnets. Can be used as a free experimentation activity. Can also be used to introduce magnetic field lines of the Sun.
    Science topic (2005 curriculum connection)
    Earth and Space Science: Stars and Planets (grade 3)
    Physical Science: Force and Motion (grade 1)
    Materials
    • various magnets (round, bar, fridge magnets)
    • iron filings sealed in a clear food container (e.g. salad/herb container) - use hot glue around the edges to seal, then shake to check for leaks; leave the white label on to show the patterns better. Alternatively, a large petri dish; attach a white label to the bottom to make the patterns show up better (though a thick label blocks some weak magnetic fields of fridge magnets)
    Procedure

    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.

    Grades taught
    Gr K
    Gr 1
    Gr 2
    Gr 3
    Gr 4
    Gr 5
    Gr 6
    Gr 7

    Magnetic fishing game

    Summary
    Students try to pick up fish with magnets. The fish have different kinds of metal at their mouths so some won't catch. Can be used as a free experimentation activity.
    Science topic (2005 curriculum connection)
    Physical Science: Force and Motion (grade 1)
    Materials
    • Paper cut-out fish, each with a paper clip, staple, safety pin (all steel) or aluminum foil strip at their mouth. Several of each kind for each student.
    • Magnet on a string, attached to a rod, for each student
    Procedure

    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.

    Notes

    Alternatively, use a commercial magnetic fishing puzzle.

    Grades taught
    Gr K
    Gr 1
    Gr 2

    Magnets: what sticks to them?

    Summary
    Students use magnets to try and pick up various materials. Can be used as a free experimentation activity.
    Science topic (2005 curriculum connection)
    Physical Science: Force and Motion (grade 1)
    Materials
    • magnets, one per student
    • materials to test, some metal, some of those containing iron. e.g. iron nail, brass screw, aluminum foil, paper clip, wood, coin, pipe cleaner, eraser, paper, copper item e.g. cookie cutter
    • non-metal trays to spread materials out in
    Procedure

    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'.)

    Notes

    We found that some pennies were attracted to the magnet and some were not. An interesting extension would be to collect many pennies, and look for a correlation between the year the penny was made and whether they are attracted to a magnet, to predict what metals are in each year. Please note on a small experiment myself that there is no clear, immediate correlation.

    Grades taught
    Gr K
    Gr 1
    Gr 2
    Gr 3

    Friction on a bike

    Summary
    Look at a bike to find all the places where friction is increased and reduced to make the bike work.
    Science topic (2005 curriculum connection)
    Physical Science: Force and Motion (grade 1)
    Physical Science: Forces and Simple Machines (grade 5)
    Materials
    • bike
    • ball bearing unit to look at closely
    • pictures of ball bearings in handle bar stem, wheels etc
    Procedure

    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.

    Attached documents
    friction_on_a_bike.pdf
    Grades taught
    Gr 1
    Gr 2

    Friction

    Summary
    First introduction to friction with nice pictures.
    Curriculum connection (2005 science topic)
    Physical Science: Force and Motion (grade 1)
    Type of resource
    Book
    Resource details

    Friction by Ellen Sturm Niz. First Facts book by Capstone Press. 2006.

    The Solar System

    Summary
    Choose a selection of activities to investigate the scale of our solar system, how we explore the solar system with rockets and gravity assist, and what planet features can tell us about the geology of a planet.
    Procedure

    Our solar system is a blip in the universe, but even our solar system is enormous. Make a Solar System to scale to give a sense of the relative size of the planets and the space between them.

    To learn about the planets in our solar system, and what is beyond our solar system, rockets take off from earth carrying unmanned probes.
    Shoot off a baking soda and vinegar rocket and/or film canisters with Alka seltzer to show the physics of how a rocket takes off. Use molecule models to show the the chemistry of a real rocket.
    Use a balloon rocket to experiment with how the weight of a rocket affects how fast it can fly, and to highlight that fuel is a significant part of the mass of a rocket.

    Once a rocket takes a space probe beyond earth’s gravity, the gravity of the sun and other planets are used to alter the path and speed of the probe, to send it to a targeted planet and/or beyond the solar system. Model with the gravity assist activity.

    The images that we get back from probes of the surface of planets help us understand the climate, geology and history of the planets and their moons. Craters are the dominant feature on many solid Solar System objects. Model crater formation to see what the features of craters can tell us about a planet's makeup. Model the formation of planet features formed by wind and flow of liquids and what they tell us about a planet's climate, geology and history.

    Optionally talk about how the solar system was formed:
    The solar system started as a cloud of gas and dust particles. Even these tiny particles have gravity and so are attracted to each other. The centre of the cloud got dense and hot enough for nuclear reactions to start (H2 fusing together), and our sun to be born.
    The remaining gas and dust was slowly attracted into the planets. The closer planets, with the warmth of the sun evaporating any water, were made from metal and rock. The outer planets, far enough from the sun for ice and small molecules to stick around, formed the large gas giants.

    Grades taught
    Gr K
    Gr 1
    Gr 2
    Gr 3
    Gr 4
    Gr 5
    Gr 6
    Gr 7
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