You are here: Index >> Science at Home >> The Science
The science behind science at home
  Investigation The Science
Sorting and Classifying The ideas of classifying and sorting are at the heart of much of science - making patterns and organising. So, we have alive, not alive and never alive, or vertebrates or invertebrates, or types of mammals are ways of organising and sorting living organisms. Transparent, Translucent or Opaque for how much light is let through. Science also likes scales such as the centigrade scale for temperature of the Scoville scale for strength of spice. This organisation or taxonomisation has given us some key science discoveries such as the periodic table or the classification of living things.

Growing a plant

Plants need some key things to grow. Light, Soil (or a nutrient source) water and air. You can grown plants without soil in a water / nutrient mixture (hydroponics) a key science for the future and for space travel. Plants also change carbon-dioxide into oxygen via gas exchange - this is the oxygen that is vital for animals (including us!).

Floating and Sinking

When an object is in a fluid (liquid of gas) it pushes (displaces) some of that fluid. The gravity effect on that displaces fluid gives the object an upward push. If that is bigger than the gravity force on the object it floats (e.g. helium balloon in air is lighter than the air it pushes out of the way). A hollow boat will push a lot of water out of the way and so will float even though the boat is made of heavy metal.

Floating Grape

So the "magic" grape is a little denser (mass/volume or amount of stuff / amount of space) than tap water but when you add enough salt to the water the salty water becomes more dense than the grape. So when you start the water pushed out of the way has less gravity force than the grape so it sinks - later on the salty water has more so it floats - science not magic!

Dancing Raisins

Bubbles of carbon-dixode will form in the wrinkles of the raisins (lots of surface area and points for them to form on called nucleation points) They act like tiny flotation devices that lift the raisin to the surface of the water. This is due to an increase in buoyancy. Once the carbon dioxide bubbles reach the surface of the soda they pop and the gas is released into the air. This makes the raisin lose buoyancy and fall back down to the bottom of the glass.

Water on a penny

There are two things going on here. The attraction between water molecules is called cohesion. The cohesive force that occurs between water molecules is so strong that, at the water's surface, it creates a "skin", which is known as surface tension. The attraction of water molecules to other substances, like soil or glass, is called adhesion. As drops of water are added onto a penny, the adhesive force between the water and the penny keeps the water from falling off. The cohesive forces between water (polar) molecules are stronger than those between non-polar molecules, such as those in oil or syrup. That's why you can make a bigger "pile" of water than of oil or syrup.
Checking out the power Electricity comes into our houses in two forms - power in the wires that has been produced in a generator far away produced by mechanical means (a magnet turning inside a coil of wire) or in a cell (battery) produced by a chemical reaction. The mains gives us more power (volts) but the battery is portable power. We can also get portable generators - you may have a "wind up torch" this is a small portable generator (which you operate by hand [mechanical] and it charges a battery [chemical])
Marble runs Gravity pulls any object with mass towards the centre of the earth (all masses attract each other and the earth is very massive). So as long as your marble run (mostly) points down the marbles will keep going. When the are moving they do 'store' movement energy (momentum) so they can use this to go against gravity for a little. Can you make your marble hop, skip and jump. If the surfaces the marble is running along are smooth (low friction) then they will not slow down (if they are rough (high friction) they will slow down quickly and may stop!
Tallest Tower Objects can be made rigid (do not bend) or flexible (do bend). Sheets of paper are very flexible but not strong. So by making tubes (or using ready made tubes [straws]) we create strong, rigid materials. However we do not want these to be damaged bent or they lost the structural integrity and will be flexible again at the point of the bend. We also want the centre of gravity (the point at which the mass of the object acts) to be inside the framework of the tower - if it is outside the tower will be subject to a turning force and will topple. This is why towers tend to be pyramids or cuboids so that this centre of gravity is in the best place.
Keeping Teddy Dry Some objects do not let water flow through them (impermeable) whereas some objects let water through (permeable). There is a scale of permeability though so some will 'resist' for a while before letting the water through. We like to use impermeable objects to keep the rain off (plastics, leather, nylons are all good.
Burn, baby burn! In order to burn there needs to be oxygen and fuel and a 'starter' (usually a flame). Some things burn (combine with the oxygen to make a new substance) more easily than others. Fats and oils burn very well and foods that contain them will burn. Others, like those that contain water, do not burn so well or at all.
Back to the Science at home page
  Investigation The Science
Balloon cars Newton's third law of motion says, 'for every action there is an equal and opposite reaction'. As the air rushes out of the balloon is one direction the car then the balloon moves in other opposite direction. You could try this if you have a skateboard or skates - stand on the skateboard and thrown a heavy object away from you - you will be propelled in the opposite direction. Once the air inside the balloon 'runs out' then the car will slow down and stop (as the friction between the wheels and the surface acts to slow it).
Musical Straws Sound is the vibration of a fluid (usually air). If we can make this vibrate a particular amount then we get sounds (like speech). As you vary the length of the wave you get different pitches (or frequency) in the straws and so different notes. If you trim theses carefully you can make a 'tuned' instrument (an agreed set of frequencies).
Singing Glasses When we tap the glass or rub a moistened finger around the rim of the glass you are making the air in the glass vibrate. This will vibrate at a particular frequency (called the resonant frequency) and so the glass will 'sing'. If you add water you change the amount of water in the glass then you change the vibration frequency.

Le Mans Maison

As we create a slope gravity pulls the car towards the centre of the earth and down the slope. The friction between the wheels and the slope slow the car down. There might also be friction on the bearings of the car and air resistance as the car comes down the slope. You can change this by oiling the bearings (lowering friction) or lowering air resistance.

Extension: A magnet produces a magnetic field which will work through nonmagnetic materials (such as card or plastic). The magnetic field attracts the magnet on the bottom of the paper car and so you can move the car through the plastic or card.

Walking Horses This is effected also by gravity which pulls the horses down the slope - as they rock (the curved feet) each foot is off the ground for a little and so will come down the slope a little as the rocking continues the horse will 'walk' down the slope.
Well Bread Bread is a good growth medium for fungus and bacteria and putting these into the plastic bags (i) gives them some moisture from the air which will help them to grow and (ii) keeps them 'pure' from any other contamination. The different rates at which the mold grows shows us the different amounts of bacteria (germs) that we have on our hands or on different surfaces and how just washing hands can kills the majority of those - important lessons in a time of Coronovirues.
Paper Spinner As an object falls through the air the air particles 'bounce' off the surface - this creates a repellent force (Newton's third law again) and so slows the object falling in a gravity field. The larger the surface of the object the slower it will fall. If we can maximise the area by not letting the spinner slip sidewards we get a better effect so twisting or bending the 'blades' can help.
Back to the Science at home page
  Investigation The Science
Don't over react! Our eyes receive sensory input and send a signal to out brains, neurons fire very quickly and send messages along our nervous system to our muscles. The rule drop measure how quickly you can react. We can get better at this with anticipation - and sometime luck!
Get over it A good measure of general fitness if called recovery rate - the time it takes our pulse rate to return to its resting rate after vigorous exercise. So, take your pules (wrist or neck are best - a pulse can be found where a vein or artery crosses over a bone, as we compress the vein or artery we can feel the pump of the heart forcing the blood though the constricted vessel). When we exercise our muscles need more oxygen so the heart speeds up pumping the blood, which carries the oxygen, to our muscles. When we rest the heart slows down again. The time between high rate and normal rate is called recovery time.
Refraction Action Light travels in straight lines - when it travels from one medium to another the light is bent or refracted. So, when the light comes though the water it is bent making the pencil look 'broken' If you try different fluids you will see the light bending different amounts.
Static Ghosts When you rub the balloon you transfer negative changes to the balloon as the balloon is placed close to the 'ghost' it pulls on the atoms in the paper attracting the paper towards the balloon - the force of attraction is enough to raise the tissue paper as it is so light. This is the same reason that a balloon will 'stick' to a wall it is the electromagnetic attraction between the particles - after a while the negative charges dissipate and so the attraction fades and the 'ghosts' will settle or the balloon fall from the wall.
Crystal Action: When you add a solid (bicarbonate of soda) to a liquid (water) you form a solution - the hot water is more energetic and so you can add more solid. When you cannot add any more solid the solution is 'super saturated'. The wool will soak up the solution and as it cools the solid will crystallize out - you should get bicarbonate stalactites hanging down and you might even get some stalagmites on the plate.
I'm not seeing it? Lemon juice is a weak acid (citric acid - C6H8O7). When diluted in water and first applied it is colourless and so when dried is invisible. As it is heated it releases carbon which oxidizes and turns brown. Other liquids will work in the same way (orange juice. milk, onion juice, vinegar and white wine).
Somewhere over the ... Water molecules have a charge and so are attracted to things including themselves. The kitchen roll has lots of tiny holes and so the water is drawn up into the roll. The water molecules drag others after them (capillary action) the water also picks up colour from the ink from the felt pens thus creating the rainbow.
Spreading out The food colouring will dissipate (spread out) in the water but not in the oil. When you put the oil onto the water it is less dense and so will float on top of the water - the food colouring will sink and then spread out in the water as the moving water molecules push the smaller food colouring molecules around (Brownian motion) - this creates the 'fireworks'
What a gas Bicarbonate of soda is a white powder with the chemical formula NaHCO3. When it reacts with Vinegar (Acetic Acid CH3COOH) and forms a new compound called sodium acetate along with water (H2O) and lots of CO2 (Carbon Dioxide) which is a gas. This gas will inflate the. balloon. Once you have inflated this if you tie off the balloon you should be able to feel that the CO2 is a heavy gas (heavier than air).
Hot Damn Sunlight contains a range of wavelengths of light including all the visible spectrum (rainbow!). The black paper absorbs all the light reflecting only a little back so is gaining all the energy. The white paper reflects most of the light so absorbs little of the energy. The light energy is converted into heat energy and so the black paper gets much hotter. This is similar for various other materials like metals who absorb the heat energy - so a black car will get very hot indeed!
Back to the Science at home page
This website has been developed by web
This page last updated Aug. 4th, 2020