See the light

Last topic… Photosynthesis.

Here’s a bit of history:

In the mid-17th Century, biologist Jan Baptist van Helmat suspected that plant growth had tocome from water, after test he conducted showed no change in soil amount. However, carbon rich organic molecules can be found in plants. Water does not provide carbon. Thus, from that point, scientists discovered that water was an important element for photosynthesis, but not the sole component. The process of making food was thus defined as photosynthesis.

Photosynthesis is a process which

• Carbon Dioxide, water and light is trapped by chlorophyll to make food in the form of Glucose, with Oxygen given off in the process.
• The chemical process of Photosynthesis is: 6 Co2 + 6 O2 — light — C6h1206 + 02.

 

Now let’s look into chloroplasts…

• Chloroplasts are disc like structures found in plant cells.
• Rows of chlorophyll are stacked up in the chloroplasts.
• Leaves are green due to the chlorophyll reflecting the green pigment of light.
• Thus, plants have near-zero growth when exposed to green light.

 

Now, glucose…

• Glucose is the basic building block of the plant. They are stored as starch when in excess.
• Potato and yams are examples of storage parts of plants.

 

Finally, stomata…

• Stomata are small openings in the structure of the leaves that allow gaseous exchange with the air.
• Flanked by 2 guard cells, each stomata open and close at regular intervals.
• These stomata are usually found on the underside of the leaves, as the underside is not exposed to as much sunlight as the topside, thus preventing water loss through evaporation.

 

Now, for a few tests…

Carbon Dioxide test:

• C02 bubbled through Calcium Hydroxide, a white precipitate will be formed in the Calcium Hydroxide.

O2 test

• O2 will relight a glowing splint
• Brighter glow is also counted as a presence of oxygen

Starch test

• A variegated leaf is destarched for 4 days, before boiled and soaked in ethanol to kill it and decolourise it.
• Next, Iodine solution is dropped onto the leaf.
• If the leaf turns brown, Starch is absent.
• If it turns blue, Starch is present

Practicals @ Science Lab

This gallery contains 9 photos.

Practical 1P17: Moving Waters. Description: To demonstrate the process of Osmosis. Apparatus: Beaker (400 cm3) Capillary tube (30 cm long) Retort stand Materials: Visking tubing (15 cm long, knotted at one end) String 50% sucrose solution Marker pen Procedures & Observations: Soaking the visking tubing under running water for 2 minutes. Remove from water when … Continue reading →

Something churning

The digestive system…

Here: Stomach

They Like To Move It

Hi all!

Third last topic before my test… Diffusion and Osmosis.

• Golden Principle: “From more to less.”
• Small molecules consist of: salt, water and glucose
• Large molecules consist of: starch, sucrose and urea

Diffusion

• Definition: “A net movement of atoms of molecules from an area with higher concentration to a region where they are at a lower concentration.”
• Concentration refers to the number of particles per unit per volume
• Diffusion will stop when the area is even concentrated
• Diffusion is a slow process

Osmosis

• Only occurs for water
• A dilute solution is one with a higher concentration of water
• A concentrated solution is one with a lower concentration of water
• Definition: “The net movement of water molecules from areas pf higher density to an area of lower concentration through a partially permeable membrane.”
• Use the term “move via osmosis”, as there is no such thing as osmosise
• Osmosis is a fast process

Now a moment for a diagram:

Diffusion and Osmosis

Solutions are also redefined here:

• An Isotonic solution is one with an equal water to solute concentration
• A Hyptotonic solution is one with a higher concentration of water than the solution
• A Hypertonic solution is one with a lower concentration of water than the solution

Did you know? An Amoeba “breathes” via diffusion.

Finally, some cell terms:

Animal

• Too much water: Lysed
• Normal
• Too little water: Shriveled

Plant:

• Turgid (Normal)
• Flaccid
• Plasmolysed

Cells

Revisit of an old topic.

Firstly, we learnt how to draw and label the cells.

Here is a diagram to show you the drawings:

Cell Structure. Note: the plant cell's small circles are actually Centrioles, not Lysosomes.

We were told not to show the start and end of our lines regardless of which part of the drawing we are covering. We were also told about the specific sizes of the various organelles in the cells.

We were also introduced to other parts of the plant cells. This included:

• Mitochondrion
• Lysosome
• Centriole
• Golgi Apparatus
• Smooth/Rough Endoplasmic Reticulum

Finally, we were told to scrape cheek cells from the inner wall of our mouth to scan under the microscope.

Pulling apart

The last topic to this long term.

Just a simple collection of diagrams and terms.

Note:

• For all diagrams, one must draw ‘n’ label.
• One must also describe the process.
• Finally, one must describe the use of the set-up.

Okay, get ready for set-up one, Filtration:

Filtration

Next, the Separation Funnel:

Separation Funnel

 

Next, Simple Distillation:

Simple distillation

 

Finally, Crystallisation:

Crystallisation

Mixing around

Solutions and suspensions…

All non-living matter can be classified into Pure substances (elements and compounds) or Mixtures. Mixtures can be further broken down into suspensions and solutions.

Here are the definition of both solutions and suspension:

• A solution is formed when the solute is completely dissolved in the solvent.
• A suspension is when the solute does not completely dissolve in the solvent.
• The solubility is the maximum of a substance in a solvent which can dissolve in 100g of solvent at a given temperature (temperature affects the movement of particles, thus affecting space between particles and the solubility of the solute. Similarly, pressure also affects the space between the particles).

Solutions are also classified into different types, depending on the concentration of the solute:

• A little amount of solute vs solvent -> dilute solution
• A solution near max solubility -> concentrated solution
• Max solubility -> saturated solution
• Over max solubility -> suspension

Solutions terms also differ:

• We never use the term “white solution” or “transparent solution”. Instead, we use “colourless” solution.
• E.g. Limewater + carbon dioxide -> white precipitate in a colourless solution, and is a suspension.

Rate of dissolving is also important:

• Firstly, one must assume that the amount of solute used, when asked, is the solubility limit, unless stated otherwise.

Factors that affect the rate of dissolving are:

• Temperature of solvent – Kinetic Particle Theory
• Particle size of solvent – Exposed surface area of individual particles
• Stirring – Distribution of particles

The Good, the Bad and the Ugly

Naah, its just the topic of Elements, Compounds and Mixtures. Prepare to be blown away.These three are the basic building blocks of matter.

*Dramatic music plays… dun dun dun*

• An atom is a single particle that is not chemically combined to anything else.
• A molecule is strand or cluster of particles that are chemically joined together
• An element describes a single type of chemical
• A compound describes multiple types of chemicals that are chemically combined
• A mixture describes multiple types of chemicals that are not chemicallt combined.

Here is an example:

Elements, Compounds and Mixtures

 

Finally, the difference between compounds and mixtures:

Compounds are

• 2 or more types of elements chemically combined together
• Examples include:

1. Element + Element -> Oxygen + Hydrogen = Water (H20)
2. Element + Compound -> Magnesium + Hydrochloric Acid = Magnesium Chloride + Hydrogen
3. Compound + Compound -> Sodium Hydroxide + Hydrochloric Acid = Sodium Chloride + Water

• Compounds are a chemical reaction. They form in fixed proportions – e.g. O2 = Oxygen, O3 = Ozone
• Different properties from it constituent elements – e.g. Sodium = explosive, Chlorine gas = poisonous, Sodium Chloride = Table salt.
• Cannot be separated by physical means.

Mixtures are:

• Not a chemical reaction
• Not formed in fixed proportions
• Similar properties to its constituent elements
• Can be separated via physical means

I Like To Move It

Hi all!

Today, we started on the topic of the Kinetic Particle Theory, or KPT for short. Essentially, it was the theory of gases which states that all particles and/or molecules in a gas are in constant random motion. This topic covered the basic knowledge of particles, before moving on into the theory of Brownian Motion.

Brownian Motion is a study on the movement of particles, as affected by their individual size, or the size of the particles around it. A Hausman Test can be carried out to study this effects. This test was done by placing a light source under smoke particles encased in an airtight translucent container, and observing under microscope.

Brownian Motion

The KPT was simple enough, only that it could be applied to other topics, such as diffusion, as well.

The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules), all of which are in constant, random motion.

– Wikipedia on the Kinetic Particle Theory