Ecosystems
Name 4 nutrient cycles of the ecosystem. (T)
1. Water cycle
2. Carbon Cycle
3. Nitrogen Cycle
4. Phosphorus Cycle
Is DDT an element, a compound, or a mixture? (K)
A mixture
What is the Big Bang? (K)
It is the event that may have triggered the expansion of the universe 14 billion years ago
Write Ohm's law in a form that can be used to calculate the potential difference? (T)
V=IR
What are the two ways of increasing the Carrying Capacity of an ecosystem? (K/U)
1. Altering an ecosystem (increasing energy and resources)
2. Altering behaviour (using resources efficiently)
Describe Bohr's model of the atom (C)
Electrons are stable in specific energy levels around the nucleus The nucleus contains neutrons and protons. Protons are positively charged, electrons are negatively charged, and neutrons are neutral. The number of protons and electrons are equal, and an atom has no charge.
Give three reasons why the Earth is round and not flat. (C)
1. When a ship sailed out, the hull disappeared below the horizon, and as it moved farther away, it disappeared.
2. When travelling north, travellers saw stars rising farther above the northern horizon. When travelling south, they saw stars they had never seen before.
3. During an eclipse of the Moon, the shape of Earth's shadow is always curved.
Compare a water tap in your home and an electrical switch. (A)
A water tap can change the amount of water that is produced (more or less), while an electrical switch is binary and can only produce the same amount of light and electricity each time.
Describe what happens during the process of Photosynthesis. (C)
Chlorophyll in leaves uses solar energy to combine carbon dioxide with water to produce glucose and oxygen. The glucose is used up by the plants as energy supply and the oxygen is released to the atmosphere.
Can two metals combine in a molecular compound? (T)
No. A molecular compound forms when when atoms share a pair of electrons to form covalent bonds. Covalent bonds are usually between two or more nonmetals.
Why did the Chinese astronomers called the 1054 supernova explosion a guest star? (T)
It remained visible for 2 years. In Chinese astronomy, a guest star is a star that suddenly appeared where no star had been previously observed and becomes visible again after sometime.
State the three laws of electric charge. (K/I)
1. Like charges repel.
2. Opposite charges attract
3. Charged and neutral objects attract each other
If you eat a bowl of salad, at what trophic level are you? (A)
Second trophic level
What negative effects do plastics have on our lives and what alternatives would you suggest? (A)
Plastics are not easily biodegradable and require lots of effort in recycling. Chemicals in the plastics slowly leach out over time in landfills. The small broken down plastics contain toxic materials that can leach into water and soil. Discarded plastics are hazardous to wildlife, on land and in ocean. The best alternative is reusable cloth bags
Why is it safe to watch an eclipse of the Moon but not an eclipse of the Sun? (A)
The eclipse of the moon is safe to watch because it does not emit radiations so it won't blind you, however an eclipse of the sun can be harmful due to the radiation that is produced.
Explain why the user of an electric lawn mower must use a thick extension cord.(C)
A thicker wire will have less resistance and will allow the required current to get to the lawn mower at far distance.