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Reflection for term 3 test

I feel that I have improved for my results from term 2 as I got c6 for term 2 and got B3 for term3. Actually, I got an A2 but as the marks were capped at 69 marks, I got a b3. I feel that I must improve and get an A1 for the year end examination.

Cells

What are cells?
Cells are the building block of life. Most animals and plants are made up of thousands of cells.
A cell is the smallest unit of life
There are two types of cells
-Plant Cell
-Animal Cell
Cells are alive. They do everything living things do to stay alive.
Cells have different parts to do all these functions.


Function of different parts of a cell

Protoplasm
A cell consist of a mass of living matter is called protoplasm
It includes the cell surface membrane, the nucleus and the cytoplasm.

Nucleus
The nucleus consist of a small spherical mass of denser protoplasm, the nucleoplasm, surrounded by a membrane called nucleus envelope.
It is embedded withing the cytoplasm and controls all cell activities.
Within the cells, there are a network of long thread-like structures called the chromatin, spgerical structures called the nicleoli and a nuclear envelope

The chromatin contain herditary materials.
The nucleolus is responsible for building up the proteins
The nuclear enveloe separates the nuclear content from the surrounding cytoplasm
The nucleus is responsible for cell production and is needed for the continued lief of the celll and the repair of worn-out parts in the cell.

Cytoplasm
The part of the protoplasm surrounding the nucleus is called the cytoplasm.
It forms the larger part of the cell and is the place where most life processes occur.

There are some important organelles embedded within the cytoplasm
-mitochondira
-chloroplast
-vacuole
-centriole
-ribosome

Mitochondria is small and sperical or rod-shaped.
It release energy from food subdtance during cell respiration

Chloroplast is the site where plants make food. It combine together carbon dioxide and watter and uses the light energy from the sun to make sugar(glucose)

Vacuole is a fluid-filled space enclosed by a membrane.
Animal cells have many small vacuoles but the are not permanent. Vacuoles contian water and food substances.
Plant cell has alarge central vacuole which contain cell sap which contains dissolved substances such a sugar and mineral salt.

Cell membrane surrounds the cytoplasm
It is a partically permeable membrane which controls substances entering or leaving the cell.

Cell wall is in the plant cell which encloses the whole cell.
It is made of cellulose and protects the cell from injury

Ribosome is the smallest organelles in the protoplasm.
It produces protein from a set of genetic instructions
It floats freely in the cytoplasm

Tissue.
Many cells make up a tissue.
Mant tissues working together will make an organ.
Many organ working together will form an organ system.
Many organ syste mwill form an organism


Tissue is a group of cells which has a commob origin and a simlar structure which enables them to perform a particular function.

Tissues of plant cell

Epidermal tissue protects the underlying cells of a leaf by preventing water los and acts as a barrier to fungi and other invaders.

Xylem Tissue transport water and dissolved mineral salts to the leaf.

Phloem tissue transpors the manufactured food away from the leaf to other part of the plant.

Photosynthetic Tissue carries out photosynthesis.

Tissues of animal cell

Epithelial tissue is a sheet of cells which covers the internal and external surface of an organ.
Functions include secretion, absorbtion, protection, trancellular transport, sense of touch.

Muscle tissue is divided into 3 main groups.
Smooth muscle tissue controls slow, involuntary movement
Skeletal muscle tissue bring about the coordinated movement of the limbs, trunk, jaws, eyeballs, etc.
Cardiac muscle tissue contract the atria and ventricles of the heart.

Connective tissue is divided into 4 main group

Dense connective tissue forms ligaments and tendons. It is densely packed amd have great tensile strength
Loose connective tissue holds organs in place.
Reticular connective tissue form a soft skeleton to support the lymphoid organs
Adipose tissue is used for cushioning, thermal insulation and energy storage.

Nerve tissue make up the nervous system that carry information within the body.

Gandular tissue forms gland that produces substance to secrete hormones or sweat.

Separation Technique

They are many different separation techniques

-Magnetic attraction

-Filtration

-Evaporation to dryness

-Distillation

-Chromatography

-Sublimation

-Using separating funnel

Magnetic attraction is used to separate magnetic objects such as steel from non-magnetic objects in a mixture

Filtration is used to separate insoluble solids from the liquid in solid-liquid mixture.

The insoluble solid left behind on the filter paper is called residue.

Evaporation to dryness is used to separated dissolved solid which does not decompose on heating

Distillation is used to separate a liquid from solid-solid solution or liquid-liquid solution

Fractional Distillation is used to separate miscible liquids with different boiling points.

Chromatography is used to separate different components in a liquid or gaseous mixture.

Sublimation is used to separate a solid which sublimes when heated.

Using a separation funnel is used to separate two immersible liquid(capable of being completely immersed in water without suffering damage), such as oil and water

Solution and Suspension

Definitions

Solute is a substance which dissolves in a liquid is called a solute

A liquid which dissolves other substances is called a solvent

A solute dissolves in a solvent to give a solution

Therefore,

Solute + Solvent ----------> Solution

IMPORTANT

30cm3 of solute + 40cm3 of solvent ≠ 70cm3 of solvent

How is a solution formed?

When a solute dissolves in a solvent, the solute particles surround each solvent particles. The particles then intermix uniformly to form the solution. The solute and solvent particles do not combine chemically.

Types of solution

• Solid-liquid solution

• Gas-liquid solution

• Solid-solid solution

• Liquid-liquid solution

• Gas-gas solution

Suspension

When a solid does not dissolve in a liquid, a suspension is formed. The solid is said to be insoluble

A suspension is a mixture of small insoluble particles in a liquid or gas.

For all solutions, there is a limit to the amount of solute that can be dissolved in a given amount of solvent at a given temperature. The limit depends on the solubility of the solute.

A saturated solution contains the maximum amount of solute that can dissolve in a fixed amount of solvent at a particular temperature.

The solubility of a solute is the maximum amount of solute that can dissolve in 100g of solvent at a given temperature.

The higher the solubility, the more soluble the substance

The strength of a solution is referred to as concentration

The concentration of a solution is the amount of solute in 1dm3 of solution

1dm3 = 1000cm3

A concentrated solution contains more solute particles in a fixed amount of solvent than a dilute solution

A concentrated solution can be made more diluted by adding more solvent

To make a dilute solution more concentrated, we can add more solute or remove solvent by evaporating the solvent.

Factors that affect the extent of dissolving

Nature of solvent

The solubility of a solute is different in different solvent

Nature of solute

Different solute have different solubility in a solvent

Temperature

The higher the temperature of the solvent, the higher the solubility of the solute

Factors that affect rate of dissolving

Temperature

Most solute dissolve faster at higher temperature

Rate of stirring.

Solute dissolve faster when the solution is stirred

Size of solute particles

The larger the surface area, the faster the rate of dissolving as smaller piece solute have a larger surface area in contact with the solvent than compared to the larger pieces of solute

Compound and Mixture

Definition of compound

Compound is a substance consisting of two or more element chemically combined together.

e.g., Sodium chloride which is made up of sodium + chlorine

Characteristic of Compound

A compound has properties that are different from the properties of its constituent elements.

When a compound is formed there is usually and exchange of energy in the form of heat or light energy or both with the surrounding.

A compound can only be broken down into simpler substances by chemical methods, such as decomposition by heat.

The different elements in a compound always join together in a ficed proportion by mass.

For example, 2g of hydrogen + 8g of oxygen form 10g of water

Mixture

Mixture consist of two or more substance not chemically combined together.

E.g., air, soil, blood.

Characteristic of Mixtures

A mixture has the properties of its components

When a mixture is produced little or no energy in the form of heat energy or light energy is given out or taken in.

A mixture can be separated into its components by physical means such as using a magnet, evaporation, filtration.

The components in a mixture can be mixed in any proportion by mass

Element

Definition of Elements

An element is a substance which cannot be split into two or more simpler substance by chemical reaction.

Every element is given a name and a chemical symbol

Elements

109 types of element have been discovered so far.

92 element occur naturally while the rest are man-made

Most element are found combined with other elements in the form of ores or minerals

This is the Periodic Table

Each vertical column is called a group

They have similar chemical properties. Each group has its own unique properties.

Each horizontal row is called a period

Elements in a period from left to right shows a gradual change from metallic preperties to non-metallic properties

In the periodic table, each element is represented by chemical symbol.

For e.g., Aluminium is called Al

Zinc is called Zn

Magnesium is called Mg

Element can be classified into Metals, and Non-metals

Properties of Metallic and Non-metallic Elements

Metallic element has high melting point and boiling point.

They are good heat and electrical conductors.

They are ductile and malleable.

They are shiny, has high densities and sonorous.

Non-metallic elements have low melting and boiling points.

They are poor heat and electrical conductors except graphite.

They are brittle

They are dull in appearance, has low densities and are not sonorous.

Classification of Matter

Matter exist in 3 state- Soild, liquid and gas.

Solid has fixed shape, fixed volume and high density

Liquid has unfixed shapes, fixed volume and has moderate density

Gas has unfixed shape, unfixed volume and has low density

The inter-conversation of states.

Melting.

When a solid is heated, heat is absorbed causing particles to increase in energy and vibrate.

Boiling.

At boiling point, particles get enough energy to overcome the forces holding them together, causing them to break away from the liquid to form a gas

Evaporation.

Evaporation takes place at the surface of the liquid.

Evaporation takes place at all temperature.

Freezing.

At freezing point, liquid turns to solid.

Heat energy is given out

Temperature stays constant while liquid freezes as heat energy is released when particles slow down to take up fixed position in the solid.

Sublimation.

Process whereby inter-conversation between solid to gaseous state without passing through the liquid state.

Heat energy is absorbed when solid changes to gas

Heat is given out when gas change into a solid

Mass and Density

Definition of mass

Mass is a measure of the amount of matter in an object

The mass of an object is constant and does not vary from place to place

The SI unit for mass is kilogram (kg)

Tonnes(t)

Kilogram(kg)

Gram(g)

Milligram(mg)

1 t = 1000kg

1kg = 1000g

1kg = 1 divided by 1000 tonne

1g = 1000mg

1g = 1 divided by 1000kg

1mg = 1 divided by 1000g

An instrument used to measure mass is called a balance

Definition of weight

Weight depends on the mass of the object and the force of gravity. It can change as the force of gravity changes

For example, if an object is 6kg on earth, it is 1kg on moon.

The SI unit for weight is newton(N)

The instrument which is used to measure weight is called a spring balance

Definition of density

Density of a substance is defined as its mass per unit volume

Different materials have different densities

The SI unit for density is kilogram per cubic metre(kg/m to the power of 3)

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When the density of an object is less than that of the fluid(liquid or gas), the object will float.

When the density of the object is more than that of the fluid, the object will sink.

Some uses of density below

•The hydrometer. Measures the density of liquids. Used to test electrical strength of accumulator

•The lactometer. Used to test the purity of milk

•The plimsolls lines. Markings on the hulls of ships showing how deep the ships may be submerged in different types of sea water safely.

•Hot air balloon. Rises in the air. Hot air is less dense than air at ordinary temperature.

• Submarine. By pumping water in and out of it, the density of the submarine changes. Hence the submarine may float or sink in water.

Physical Quantities and Units

The basic quantities and Units are the System International of Units, also called the SI units.

It makes up of 7 base quantities and units. They are as below

Base quantity Base Unit

Name Symbol Name Symbol

time t second s

length l metre m

mass m kilogram kg

temperature T,0 kelvin K

electric current I ampere A

amount of substance n mole mol

luminous intensity I_v candela cd

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These SI units are used very accurately all around the world

All other physical quantities are known as derived quantities. Both quantity and its unit are derived from a combination of base units by using a defining equation

For example, acceleration= change in velocity(m s-1) divided by time taken(s)

Combining the units in the defining equation gives us the derived unit of acceleration

For very large or very small numbers, we can use standard prefixed with the base units. The followings are the prefixes

Prefix Symbol Multiplier

giga G 10 to the power of 9

mega M 10 to the power of 6

kilo k 10 to the power of 3

milli m 10 to the power of -3

micro µ 10 to the power of -6

nano n 10 to the power of -9

pico p 10 to the power of -12

femto f 10 to the power of -15

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There might be errors in the experimental methods or equipment where readings are either too big or too small.

For example, if your newton-meter reads 0.2 N with no weights on it, then your measurement of force will always be 0.2 N too large

These are called zero errors

Summary of topics covered in school

These are some of the topics I had covered in school

1) Physical Quantities and Units

2) Mass and Density

3) Classification of matters

4) Elements

5) Compound and mixture

6) Solution and suspension

7) Separation techniques

8) Cells

9) Photosynthesis

10) Respiration

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Sometimes, I will not be quite sure of some of the definitions of the science terms

eg. Suspension, solution, mixture, compound. I will mix up all of these terms.

eg. The periodic table. I will not know which is period and which is row. Also, I am not sure of the uses of the row and periods.

For the following posts, I will explain about the topics I had learnt