Term 1 Reflection

In Science for term 1, we did chemistry. We did three topics: Acids alkali bases, equation writing, and chemical bonding. I preferred the acids alkali bases topic, as it was rather interesting and fun. We did a number of experiments that had to do with mixing an acid with a metal, and other stuff. I was particularly fascinated when we put hydrochloric acid and magnesium together. There was a rather cool reaction which produces hydrogen gas, with magnesium chloride. Then, we had to test for hydrogen, which was to place a glowing splint near the solution. If a 'pop' sound was heard, that means that hydrogen was present. When we did the test, we did not know that we would hear such a pop sound, and were startled when it happened. After that, we laughed happily. Although I did not quite like chemical equation as it was very difficult, I do not know why but still like chemical bonding. For me, I found it quite easy, as well as interesting, and I also felt that it was quite fun to draw our electrons. All in all, I liked chemistry in Term 1, and also did well for my test, and hence I feel really happy.

Reflection of light

Light:

v  Is the form of energy that enters our eyes

v  Enables us to see things

v  Can either be directly obtained from a luminous source or reflected off a non-luminous source into our eyes

v  A luminous source is an object that emits its own light such as the Sun

Reflection:

v  Incident ray

Ø  Ray of light that strikes the surface

v  Reflected ray

Ø  Ray of light that is reflected off a surface

v  Normal

Ø  Imaginary line that is perpendicular to the surface at the point of incidence

v  Angle of incidence

Ø  Angle between the incident ray and the normal

v  Angle of reflection

Ø  Angle between the reflected ray and the normal

Diffused reflection and specular reflection:

v  Diffused reflection

Ø  Reflected in all different directions

Ø  Produces a distorted image

v  Specular reflection

Ø  Reflected in the same direction

Ø  Produced a clear image

Image characteristics of mirror:

v  Image is formed in mirror as

Ø  Light rays reflect off you

Ø  Strikes the mirror

Ø  Goes back into your eyes

v  Image formed in  plane mirror

Ø  Has the same size as the object,

Ø  Is as far behind the mirror as the object is in front of the mirror,

Ø  Has the same orientation as the object (i.e. upright if the object is upright),

Ø  Is laterally inverted,

Ø  Is virtual.

v  Virtual image cannot be captured on a screen because no actual light rays meet at the image position.

v  Plane mirrors

Ø  Object position: anywhere

Ø  Image position: as far behind the mirror as the object is in front of it

Ø  Image type: virtual

Ø  Image orientation: same as object

Ø  Image size: same as object

v  Concave mirrors

Ø  Near mirror (inside F)

§  Image position: on the opposite side of the mirror as the object

§  Image type: virtual

§  Image orientation: same as object

§  Image size: larger than object (magnified)

Ø  Exactly at F

§  Image position: at infinity

§  Image type: -

§  Image orientation: -

§  Image size: -

Ø  Object distance less than     image distance (outside F)

§  Image position: on the same side of the mirror as the object

§  Image type: real

§  Image orientation: opposite of object

§  Image size: larger than object

Ø  Object distance is equal to image distance (outside F)

§  Image position: on the same side of the mirror as the object

§  Image type: real

§  Image orientation: opposite of object

§  Image size: same as object

Ø  Object distance greater than image distance (outside F)

§  Image position: on the same side of the mirror as the object

§  Image type: real

§  Image orientation: opposite of object

§  Image size: smaller than object

v  Convex mirrors

Ø  Object position: anywhere

Ø  Image position: on the opposite side of the mirror as the object

Ø  Image type: virtual

Ø  Image orientation: same as object

Ø  Image size: smaller than object

Ecology

Introduction:

v  What is ecology?

Ø  How life processes have adapted to its environment

Ø  How organisms are distributed in various environments

Ø  How materials and energy is moved through systems of interacting organisms and their environment

Ø  How an ecosystem changes over time

Ø  How biodiversity is influenced by the environment

v  Scales and level of complexity

Ø  Individual

Ø  Population

Ø  Community

§  Is an assemblage of two or more populations occupying the same area

Ø  Ecosystem

Ø  Biome

Ø  Biosphere

v  Examples of biomes

Ø  Desert

Ø  Savanna

Ø  Boreal forest

Ø  Intertidal zone

Ø  Tropical rainforest

Ø  Coral reef

v  Factors influencing ecology

Ø  Abiotic factors

§  Temperature

§  Rainfall

§  Light intensity

§  Salinity

§  Humidity

§  Wind speed

§  Wave action

§  pH

Ø  Biotic factors

§  Abundance of prey

§  Presence of predators

§  Competition

Ecological Interactions:

v  Mutualism

Ø  Both organisms A and B benefit from the interaction between them

§  Clownfish and sea anemone

§  Ants and aphids

§  Egyptian plover and crocodile

§  Cleaner shrimps and eel

v  Commensalism

Ø  Only organism A benefit from the interaction between them, while organism B receives no advantage or disadvantage

§  Epiphytes and rain tree

§  Cattle egret and cattle

§  Remora and shark

§  Barnacles and scallop

v  Exploitative relationships

Ø  Only organism A benefit from the interaction between them,  while B is harmed in some way or may even die from the relationship

§  Predation: Cheetah and gazelle

§  Herbivory: Zebra and grass

§  Parasitism: Tree ear fungus and tree

v  Competition

Ø  Both suffer some form of disadvantage

§  Great blue heron,  great egret and snowy egret hunting fish

§  Reindeers competing for their mate

§  Trees competing for light

Energy and Productivity

v  Food Chain

Ø  Producers: Plants

§  Obtain energy directly from the sun

Ø  Primary consumers: Herbivores

§  Obtain energy indirectly from the sun

Ø  Secondary consumers

§  Obtain energy indirectly from the sun

v  Dietary

Ø  Herbivores

§  Have a strict diet consisting of plant material only

Ø  Carnivores

§  Have a strict diet consisting of the flesh of other animals

Ø  Omnivores

§  Have a diet of both plant material and flesh of other animals

v  Decomposers

Ø  All organisms will die eventually

Ø  Bodies will undergo decomposition

Ø  Will be broken down into simpler substances

Ø  Accelerated by decomposers

Ø  Are organisms that feed on dead plants and animals, breaking them down into simpler substances

v  Non-cyclic flow of energy

Ø  Energy is always lost along a food chain

Ø  Cannot be recycled

Ø  Gets lost through the form of heat and other life processes

Nutrient cycles:

v  Carbon cycle

Ø  Carbon dioxide in water precipitate to form limestone

§  Plants take up carbon dioxide and convert it to carbohydrates

·         Carbohydrates could be:

¨       Sent back to the atmosphere through respiration

¨       Be present in the plant when it dies

Ø  Respired by decomposers

Ø  Buried and turn into fossil fuels

§  Burn fossil fuels and release carbon dioxide in the air

¨       Eaten by an animal 

Ø  Sent back to the atmosphere through respiration

§  Taken up by plant through photosynthesis

§  Dissolved in the oceans

¨       Be present in the animal when it dies

Ø  Respired by decomposers

Ø  Buried and turn into fossil fuels

§  Burn fossil fuels and release carbon dioxide in the air

v  Nitrogen cycle

Ø  Nitrogen gas in air

§  Lightning can turn it to nitrate

§  Nitrogen fixing bacteria fix it to nitrate or ammonia

·         Plants take up nitrate and convert it to amino acids

¨       Eaten by animals

Ø  When die, ammonia released back into soil

§  Nitrite bacteria change ammonia to nitrite

·         Nitrate bacteria change nitrite into nitrate

Conservation:

v  Why must we conserve?

Ø  Prevent extinction

Ø  Maintain stability in ecosystem

Ø  Maintain large gene pool and preserve useful genes

Ø  Sources of raw materials

Ø  Scientific value

Ø  Recreational purposes