Q&A - PSLE Science

[pecalis]

BeContented:

verykiasumummy:

[quote=\"BeContented\"]Question : Children inherit characteristics from their parents. How do parents pass on their characteristics to their children? (2m)


Answer key given :
The nucleus of a sperm contains genetic info/hereditary materials from the father/male parent. (0.5). The nucleus of an egg contains genetic info/hereditary materials from the mother/female parent (0.5). When a sperm fuses with an egg, a fertilised egg is formed. (0.5) The fertilised egg will divide an develop into a baby that carries the characteristics from both parents. (0.5)

Wah.....so much for 2m.

DS answer was : The nucleus of the parents' reproductive cell contains genetic information. During fertilisation, the reproductive cells fuse and the nucleus fuses and their characteristics are in their combined nucleus.

errrr.....in your opinion, is my DS answer considered complete? Should I ask him to elaborate more?

1st part of answer = ok.

keyword : sperm and egg should be inside the answer.

\"their characteristics are in their combined nucleus.\" technically doesnt sound right, both cells fuse, but not exactly that the nucleus fuse. should just say, \"during fertilisation, the egg cell from mother and sperm cell from father fuse and pass their characteristics to their offspring.\"

Thank you very much. Now is the blind (me) leading the color blind (DS better than me, can see, just color deficient). I need to look for gaps at Buddha leg :oops:[/quote]Fertilisation occurs when the nucleus of sperm fuses with the nucleus of egg. Child's answer is correct, not just fusing (or fusion?) of sperm and egg but the fusing of both nuclei.

This is my understanding from my son's Sc notes.

[ruohoo97]

charsen:

Ive tried my best to answer. Let me know if you find any of them wrong.
Q1 Why doesn't the bird get electrocuted when it stands on the power line?
Birds do not get electrocuted when it stands on the power line. Electricity passes through CLOSED circuit. When the bird sits on the powerline, it only touches only point and does not complete the circuit. Usually one end of the electric circuit of powerlines will be buried under earth. As long as any part that conducts electricity does not touch the end of circuit in earth, should be safe.

Q2Are the magnetism of a ring and button magnet even?
No.
The attraction of a magnet is strongest at the poles. Both button, ring magnets have poles and hence the magnetism is not even.

Q3 what do the organisms compete for in the pond?(when overcrowded)
Pond organisms compete for sunlight, space and oxygen. and nutrients.

Q4 what is the energy conversion when someone flies the kite?
the kinetic energy of wind to gravitational potential energy of kite

Q5 do 2 objects have friction when they are in contact with each other?
Yes. Friction exists between 2 objects in Contact. Note: (From PSLE revision guide, Friction occurs in both stationary object (static friction) and moving objects (kinetic friction).

Q7 will expansion cause an increase in mass of an object?
No. Expansion of matter does not cause an increase in mass. Mass of an object is constant regardless of where the object is. Only when we add or take away some of the matter, the mass would change.

Q8 how do animals get oxygen underground?
Underground (Burrowing) animals mix air with soil as they burrow and obtain oxygen from the air in soil.

Q9 what are the factors for decomposition to occur?
Under favourable temperature, Air and moisture decomposition occurs.

Q10 does oxygen pass thru the circulatory and digestive system?
Oxygen pass through circulatory but not digestive system. Oxygen is exchanged between the cells of the body through the blood vessels (which are part of circulatory system)

[Studious Alien]

Ready2WORK:

balu_priya:

Please help.


1)which one of the following statements Best describes a characteristic of living things?
1.living things cannot survive in the absent air.

Living things may have the ability to give birth to young ones.alive
Living things move from place to place in search of food.
Living things can live in the presence of large amount of water.



2.two ice cubes were stacked and a pushing force exerted from the top. After one minute , both ice cubes could be lifted off the surface by just
Holding the top of ice cube.

The process that resulted in the ice cubes 'sticking'together is/are ...........
1.melting
2.freezing
3.melting and freezing
4.evaporation and freezing

Q1) 1
Animals and plants cannot live in the absence of air, so Option 1 is correct. Option 2 only applies to mammals, not all living things. Option 3 only applies to animals, which can move from place of place by themselves. Lastly, Option 4 only applies to aquatic animals and plants. Therefore, answer is 1 as it best describes living things.
Q2) 3
The ice cubes melted, turning into liquid state, then due to it losing heat to the ice cubes, it froze again, joining the two ice cubes together. So answer is 3.

I do not understand your explanation for Q2.What is the 'it' in the first line? Please explain in a more detailed way. Thanks.

Regards,
Studious Alien

[verykiasumummy]

Studious Alien:

Ready2WORK:

[quote=\"balu_priya\"]Please help.


1)which one of the following statements Best describes a characteristic of living things?
1.living things cannot survive in the absent air.

Living things may have the ability to give birth to young ones.alive
Living things move from place to place in search of food.
Living things can live in the presence of large amount of water.



2.two ice cubes were stacked and a pushing force exerted from the top. After one minute , both ice cubes could be lifted off the surface by just
Holding the top of ice cube.

The process that resulted in the ice cubes 'sticking'together is/are ...........
1.melting
2.freezing
3.melting and freezing
4.evaporation and freezing

Q1) 1
Animals and plants cannot live in the absence of air, so Option 1 is correct. Option 2 only applies to mammals, not all living things. Option 3 only applies to animals, which can move from place of place by themselves. Lastly, Option 4 only applies to aquatic animals and plants. Therefore, answer is 1 as it best describes living things.
Q2) 3
The ice cubes melted, turning into liquid state, then due to it losing heat to the ice cubes, it froze again, joining the two ice cubes together. So answer is 3.

I do not understand your explanation for Q2.What is the 'it' in the first line? Please explain in a more detailed way. Thanks.

Regards,
Studious Alien[/quote]maybe i can help.

both the ice cubes melted at their contact surfaces, hence changes its state to liquid. due to some of the liquid on the surface of both ice cubes losing heat to the ice cubes again, it changes its state back to solid, hence joining the two ice cubes together.

[verykiasumummy]

pecalis:

Fertilisation occurs when the nucleus of sperm fuses with the nucleus of egg. Child's answer is correct, not just fusing (or fusion?) of sperm and egg but the fusing of both nuclei.

This is my understanding from my son's Sc notes.

yes u are right, dunno what i was thinking just now.. but my ds did mention something like \"the combination of the nuclei from both parents contains characteristics...\" and the teacher mark it wrong. i couldnt rmb the exact reason that the teacher gave, but my ds was taught to just say, \"the egg cell from mother and sperm cell from father fuse during fertilisation and pass their characteristics to their offspring.\"

hope it helps.

[Studious Alien]

verykiasumummy:

maybe i can help.

both the ice cubes melted at their contact surfaces, hence changes its state to liquid. due to some of the liquid on the surface of both ice cubes losing heat to the ice cubes again, it changes its state back to solid, hence joining the two ice cubes together.

Thank you very much verykiasumummy.

[verykiasumummy]

Studious Alien:

verykiasumummy:

maybe i can help.

both the ice cubes melted at their contact surfaces, hence changes its state to liquid. due to some of the liquid on the surface of both ice cubes losing heat to the ice cubes again, it changes its state back to solid, hence joining the two ice cubes together.

Thank you very much verykiasumummy.

no thks... was just trying to help...

[NY1969]

Can someone ans this question in a scientific way:-


A metal rod is partially is submerged into an ice water. After sometimes, why is the other end of the rod becomes cool also?

[G Tan]

NY1969:

Can someone ans this question in a scientific way:-


A metal rod is partially is submerged into an ice water. After sometimes, why is the other end of the rod becomes cool also?

question is not clear.. what you mean by the othr end?

[ruohoo97]

NY1969:

Can someone ans this question in a scientific way:-


A metal rod is partially is submerged into an ice water. After sometimes, why is the other end of the rod becomes cool also?

Because metal is good conductor of heat. It transmits heat more quickly so you will feel the other end getting cold too. Note here, the feeling of cold reflects the difference of temperature.