SA1 Practice Paper (XN) Booklet A

Dear 6A pupils,

Below are the answer key for Booklet A.

Question 1 (2)

Question 2 (2)
- At point P, % of carbon dioxide is the lowest. This shows that carbon dioxide is used up by the plant. The plant takes in the gas for photosynthesis. Photosynthesis only happens in the presence of light, hence it must be day time at point P.

Quesiton 3 (4)

Question 4 (1)

Question 5 (will go through after next chapter)

Quesiton 6 (simple machine - not in syllabus)

Quesiton 7 (4)

Question 8 (3)

Question 9 (4)

Quesion 10 (4)

Question 11 (2)
Friction (one force) moves in opposite direction of motion (one force).

Question 12 (1)

Quesiton 13 (2)
Guppy give birth to its young alive.

Quesiton 14 (4)
Everything must be kept the same except the type of metal (that is the aim of the experiment)

Question 15 (1)

Quesion 16 (3)
X- digestive juice needs to be produced for the body to digest the food eaten
Y - digested food is absorbed into the blood stream after digestion
Z - water is absorbed at the large intestine

Question 17 (3)
Bulb Y is the bulb that obstruct the current flow from the battery.

Question 18 (2)

Quesiton 19 (3)
Aphids feeds on plants. As Aphids increases, plants will decrease.

Question 20 (2)

Question 21 (4)

Question 22 (3)

Question 23 (1)

Quesiton 24 (3)
With the same amount of heat from the iron block, water in beaker C will show the greatest rise in temperature.
Heat flows from a hotter object to a colder object. In A, the temp of water is 90 but iron block is 80. Heat will flow from the water to the block. Hence in A, the temp of water will drop a little.
As for C and D, the temperature rise in water of beaker D is lower as more need is needed from the iron block to heat up the greater amount of water.

Question 25 (1)

Question 26 (2)

Question 27 (2)
B- decrease in food supply
D- increase in predator

Question 28 (will discuss in next chapter)

Question 29 (will discuss in next chapter)

Question 30 (4)
Temp decrease, the time taken for food to decay is increase (food stayed fresh longer)

That's all.


Happy Revising


Love,
Mdm Goh

Friction for Children: 4 Tricks to Help Children Understand Friction

Friction for Children: 4 Tricks to Help Children Understand Friction

Friction for Children: 4 Tricks to Help Children Understand Friction

Friction for Children: 4 Tricks to Help Children Understand Friction

Topical Test 3 Answer Key

1. DAM Question

b) (as explained on Monday, below is the answer)
The lower the opening, the greater kinetic energy the water has to spurt further.
Hence, the dam is built at the bottom as the running water has more kinetic energy to be used to generate electricity.

2. Solar Calculator

a) What kind of energy does it use?

Answer : Solar Energy or Light energy

b) from where does the solar calculator get its energy?

If your answer in (a) is Solar energy, then the source is the Sun.
If your answer in (a) is Light energy, then the source can be the Sun or Lamp.

c) state the conversion of energy that take place

Whenever we answer conversion of energy question, we need to look at how the solar calculator operates.
EXPLANATION:
To operate the solar-powered calculator, the source comes from the Sun or Light (Light or Solar energy). The calculator is an electrical device that works on electricity (Electrica energy).
Answer : Light energy / Solar energy --> Electrical energy

3. Wind turbine

a) what kind of energy does a wind turbine use?
WRONG : Wind Energy. We do not use Wind energy in our Syllabus even though we often see it in books.
Answer : Kinetic Energy from the wind.

b) how does a wind turbine generate electricity?

Whenever we answer how or why question involving energy, we need to mention the energy involved in the process.

Answer : The kinetic energy of the wind causes the rotors of the windturbine to move. As a result, the kinetic energy of the turbine is converted into kinetic energy in the generator which created electricial energy as a result.

Pressure vs Height

Maglev Wind Turbine

Sources of Energy

Wind

- Wind has provided energy for thousands of years.
- Wind is a renewable energy source, it never runs out.
- Wind is moving air.
- Wind farms in California make use of moving wind to turn the blades of turbines. The turbines are connected to a generator that creates electricity.
- The turning sails of windmills used to drive machines help people grind corn. The sails of the windmills are pushed around by the wind. Then they turn the wheel inside.
- Some modern cargo ships reduce fuel costs by using the wind to blow large rectangular sails. The sails are mechanically operated. They do not need large crews to work them as they did on the old sailing ships.
- The blades of the windmill spin the fastest if they are facing straight into the wind.

Advantages
- using wind to create electricity does not cause air pollution like burning of fossil fuels.
- It is a renewable source of energy and doe not run out. It can be used for a long time.


Disadvantages
- There is lack of wind in some countries. Some countries do not have wind strong enough to turn the turbine, to create electricity.
- It costs money to build the wind turbines.
- The building of wind turbines require a lot of space. Some countries have very little land.


COMMENT by Group

In future, wind will be one of the world's main sources of energy because it is safe, cheap and clean.


HYDRO-POWER

- We use the power of water to make electricity by building huge dams across rivers.
- The rushing water turns the blades of a turbine. This drives a generator, which produces electricity.


Advantages

- Water is everywhere. It will never run out. Water can be used to work for us.
- It will not cause water pollution


Disadvantages
- It occupies a lot of space.
- It may upset the eco-system