Q&A - P3 Science

[just888]

bebebub:

atutor2001:

[quote=\"bebebub\"]Can someone kindly help me with this question on Material:

Ships are made of heavy metals such as steel. Explain why they are able to float. TIA

A ship can float because the total volume of the ship is very big, which is made up of the steel and the air space in the ship. This increase in volume of the ship makes the mass per unit volume (called density) of a ship smaller than the mass per unit volume of water. For example, 1 cubic metre of water weighs 1 ton. If 1 cubic metre of a ship is say 0.5 ton, than the ship will float.

When the air space inside the ship is replaced by cargoes, the density of the ship will increase because cargoes is heavier than air. So a ship can only be loaded to a limit where the density i.e. 1 cubic metre must be less than 1 ton. Otherwise it will ship.

In short, a ship is able to float because a large part of its volume is filled with air, which is much lighter than water.

Thanks! Hope my dd can understand this.[/quote]Is this an exam questions? Kinda of chiem for a P3.

[just888]

smartmummy:

Thanks champ,just4Good and jedamum

Yup I know that they can't make their own food as they don't have chlorophyll.
So they are not plants but they are living things need air to grow.
In the process skills of diversity - My PALS are Here (school) book,they want to findout \"Does mould need warmth to grow?\"
The result was given \" he should observe bread mould growing only on the bread that is exposed to sunlight.
I checked in the past paper qns that include some experiments,
one piece of wet bread put in 4 degree C and another one put in room temprature.The answer was the one in room temprature. They no need direct sunlight like plant but they need warmth.
Of cause they need food saurce to grow as they feed on dead or alive animals and plants.

i think like the seeds need some warmth to grow, too cold unable to do so. Here is what I got from the wwb: Why does mold grow better in warm places? http://wiki.answers.com/Q/Why_does_mold_grow_better_in_a_warm_area

[cimman]

bebebub:

Can someone kindly help me with this question on Material:

Ships are made of heavy metals such as steel. Explain why they are able to float. TIA

to determine if an object sinks or float, one has to determine the average density of the material. Ships, while made of steel, has an average density (including air that is inside the ship) that is less than that of water.
Anything which has an average density less than water will float.
So to design a ship that floats, one has to ensure that the ship contains enough air pockets so that it's average density will be less than water's density.

Another point to note about floatation it is that the force that water exerts which causes objects to float. When an object is submerged, water exerts an upward force on that object. The larger the object's surface area is in contact with water, the more upward force the object experiences. Thus, the shape of a ship's submerged portion plays a part in the floatation of the ship, in addition to the average density of the ship.

In P3, they would not have studied density. In this case, you can explain that ships float because they are hollow. Most objects will float if the volume of empty space it contains, is greater than that of the volume of the material.

[momresource]

I need advice on the title of the P3 science textbook used in school. Does it come with accompanying workbook? Could I find them in Popular? Many thanks!

[Andaiz]

momresource:

I need advice on the title of the P3 science textbook used in school. Does it come with accompanying workbook? Could I find them in Popular? Many thanks!

Yes, you can get them at Popular 5% discount if you are a member.

There are a couple of titles/textbooks. The accompanying workbooks are sold separately. You may want to follow the book list of your kid, or something different to give a better viewpoint

[Super.049652kiasu]

Do your have any questions? I am quite good at science. If I can’t answer I will google it.

[smartmummy]

Super.kiasu:

Do your have any questions? I am quite good at science. If I can't answer I will google it.

Thanks for willing to help.Appreciates

I have a qn. This is not from P3 syllabus. We like to do experiments at home.Today we put egg (tooking from room temprature) in the tap water it sinked.Then we took an egg from freezer and put in the same water.It floated.What could be the reason?

[mother777]

smartmummy:

Super.kiasu:

Do your have any questions? I am quite good at science. If I can't answer I will google it.

Thanks for willing to help.Appreciates

I have a qn. This is not from P3 syllabus. We like to do experiments at home.Today we put egg (tooking from room temprature) in the tap water it sinked.Then we took an egg from freezer and put in the same water.It floated.What could be the reason?

Hi Smartmummy,

this is the explanation i found online when i searched for sinking or floating of eggs.

\"A very fresh egg will immediately sink to the bottom and lie flat on its side. This is because the air cell within the egg is very small. The egg should also feel quite heavy.

As the egg starts to lose its freshness and more air enters the egg, it will begin to float and stand upright. The smaller end will lie on the bottom of the bowl, whilst the broader end will point towards the surface. The egg will still be good enough to consume, however, if the egg fully floats in the water and does not touch the bottom of the bowl at all, it should be discarded, as it will most likely be bad. \"

[atutor2001]

mother777:

Hi Smartmummy,

this is the explanation i found online when i searched for sinking or floating of eggs.

\"A very fresh egg will immediately sink to the bottom and lie flat on its side. This is because the air cell within the egg is very small. The egg should also feel quite heavy.

As the egg starts to lose its freshness and more air enters the egg, it will begin to float and stand upright. The smaller end will lie on the bottom of the bowl, whilst the broader end will point towards the surface. The egg will still be good enough to consume, however, if the egg fully floats in the water and does not touch the bottom of the bowl at all, it should be discarded, as it will most likely be bad. \"

Just a little elaboration on how more air can enter the egg and how it is link to putting egg in the refrigerator.

There is water in the contents of an egg. Overtime, some of the water in the egg will evaporate. Air will then enter to take its place. Therefore, the weight (or density) of the egg will decrease and will finally be able to float.

Now on the effect of placing egg in a refrigerator. The humidity (amount of water vapour) of the air in a refrigerator is very much lower than outside air because when the air inside the fridge is cooled, the water vapour will condense. (long time ago, there is a tray in every refrigerator to collect condensate) As we know, when the humidity is low, the rate of evaporation will increase. Therefore, the rate of evaporate of the water in an egg kept in a refrigerator will be faster than another one left in the open. This explains why egg will be able to float if you keep it in a refrigerator.

[smartmummy]

mother777:

smartmummy:

[quote=\"Super.kiasu\"]Do your have any questions? I am quite good at science. If I can't answer I will google it.

Thanks for willing to help.Appreciates

I have a qn. This is not from P3 syllabus. We like to do experiments at home.Today we put egg (tooking from room temprature) in the tap water it sinked.Then we took an egg from freezer and put in the same water.It floated.What could be the reason?

Hi Smartmummy,

this is the explanation i found online when i searched for sinking or floating of eggs.

\"A very fresh egg will immediately sink to the bottom and lie flat on its side. This is because the air cell within the egg is very small. The egg should also feel quite heavy.

As the egg starts to lose its freshness and more air enters the egg, it will begin to float and stand upright. The smaller end will lie on the bottom of the bowl, whilst the broader end will point towards the surface. The egg will still be good enough to consume, however, if the egg fully floats in the water and does not touch the bottom of the bowl at all, it should be discarded, as it will most likely be bad. \"[/quote]I also found this.Thanks.