kuala lumpur, malaysia formative assessment: i 7-understanding matter_… · the atomic theory of...

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FORMATIVE ASSESSMENT: I CLASS : VII Ref.: SCI7/ FA I/ HD2/16-17 NAME : SUBJECT: Physical Science TOPIC : Understanding Matter DATE:

The Atomic Theory of Matter states that matter consists atoms that make up the molecules.

The Quantum Theory states that the particles of matter can also be in the form of waves.

Everything in this universe is made up of material which scientists have named “matter”. Matter is

anything that has mass and occupies volume. All the things we come across in our daily life are

matter.

It can be a water drop or a cup of tea or ice. Matter is made up of particles, like sand, sugar, salt.

The particles of matter are very small, smaller beyond our imagination. Matter is made up of atoms

and molecules .Atom is the smallest unit which cannot be divided further into smaller particles.

Billions and billions of atomic particles are clubbed together to form the matter that we see around

us. These atoms combine together to form molecules. For example, in water we have two atoms of

Hydrogen combining with one atom of Oxygen to form one molecule of water. Atoms have sub-

atomic particles like protons, electrons and neutrons with protons and neutrons embedded inside

the core of the nucleus and electrons orbit around the nucleus.


States of Matter

The clouds are made up of matter, the earth is made up of matter. Matter also has states, such as

being solid, liquid, gas, plasma and a new one called Bose-Einstein condensates.. As of 1995,

scientists have identified five states of matter.Matter can change states as well as participate in

chemical changes, depending on their chemical properties and composition.

5 States of Matter

The Five States of Matter are:

1. Solid

2. Liquid

3. Gases

4. Plasma

5. Bose-Einstein condensate.

1. Solid State

Out of the three states of matter, solids are more common than liquid and gas. The main point in

which a solid differs from the other two states is the fact that gases and liquid possess fluidity i.e.

they can flow and are described as being fluid, while solids do not possess fluidity; instead they are

rigid in nature. The rigidity of solids is due to the presence of strong intermolecular force between

their constituent particles. Hence particles are not free to move and they oscillate at their fixed

positions only. Because of rigidity, solids have a definite shape and volume. Hence solid can be

defined as the state of matter which possesses rigidity, definite shape and definite volume. For

example; A bar of steel, Wood block.


2. Liquid State

The liquid state lies between the two extremes of ordered arrangement of solids and disorder in

gases. The close packed structure of solids exists to some extent in the liquid state also. But liquid

exhibits only a short range of ordered arrangement and is also termed as condensed gas or molten

solids. In liquid state, the molecules are not as rigid and fixed as in solids.

They have some extent of freedom of motion, because of which they have a definite volume but no

definite shape. Liquid state is much less compressible and far denser than a gas. The

intermolecular force of attraction is only temporary in liquid state which allows it to move freely

resulting in a limited degree of particle mobility.


2. Gas State

The main difference between gas and other states is that gas molecules move around much more.

The random movement of constituent particles in gaseous state is due to negligible

intermolecular force of attraction. Due to this, intermolecular distance between molecules is very

high. They do not have definite volume or shape. Due to very large intermolecular distance,

gaseous state is highly compressible and easily compressed at high pressure for transportation.

Compared to solid and liquid state, the effect of change in pressure and temperature is more on

gaseous particles within a certain volume. Due to random motion in particles, gaseous state shows

diffusion throughout any container.


4.Plasma State

Plasma is a state of matter in which all matter is ionized and it occurs in the form of ions and

electrons. Since, we know that for the ionization of the element or matter to occur energy is

required to pull the electron from the attraction of the nuclear charge, high energy is required. So for

the ionic state to exist in nature, a very high level of energy is required. The normal temperature

range in which a plasma can exist is around 6000K. But such a high temperature does not exist in

the natural condition. So the plasma state does not occur naturally on earth.

Plasma is considered as the fourth state of matter along with gases, liquids and solids. Plasma is

sometimes considered as the ionized gases. In physics and chemistry the plasma is considered as

the portion of the gas which is ionized. The ionization of the substance can be done by many

modes, not only by heating but also by applying strong electric field coupled with laser or

microwave region.

Like gases, plasma does not have definite shape or volume, they take up the volume and the shape

of the container. It can be considered that plasma state is gaseous state at high temperature and so

it has some of the properties of gases.

5.Bose-Einstein condensate:

At ordinary temperature gas will moving in random direction. These gas molecules will be moving

with different speed depending on the energy they possess. Example: Molecules moving will higher

speed will be possessing higher energy than other molecules which are moving with the lower

speed.

If we cool these molecules we could see that the atoms slow down. Bose and Einstein predicted

that if a gas made of indistinguishable atoms is sufficiently chilled, a significant fraction of the

particles will settle to the lowest energy. That is, atoms can be forced into their lowest energy state


at a temperature above absolute zero. When particles reach this state, they form a new form of

matter called a Bose-Einstein condensate.

Change of State

Let us see the following example for this:

1. When water is given heat at a certain temperature it starts getting vaporized. This takes

place at constant temperature known as the boiling point. It is nearly 1000 C at normal

pressure. Water can also be vaporized at a lower temperature by lowering pressure.

2. Ice can be converted into water at a fixed temperature known as melting point which is 00 C

at ordinary pressure. If the pressure is increased ice can melt at a lower temperature than

00 C. However, at a given pressure the temperature of the substance remains constant until

the change of state is complete.

3. Similarly steam can be condensed into water and water can be freezed into ice at the

respective temperatures.


Exothermic and Endothermic reaction

An exothermic process releases heat, and causes the temperature of the immediate surroundings to

rise. An endothermic process absorbs heat and cools the surroundings.

A pure substance:

cannot be separated into 2 or more substances by physical or mechanical means

is homogeneous, ie, has uniform composition throughout the whole sample

its properties are constant throughout the whole sample

its properties do not depend on how it is prepared or purified

has constant chemical composition

A mixture:

can be separated into 2 or more substances by physical or mechanical means

displays the properties of the pure substances making it up

its composition can be varied by changing the proportion of pure substances making it up

heterogeneous substances, ones with non-uniform composition throughout the sample, are

always mixtures

Exothermic processes Endothermic processes

making ice cubes melting ice cubes

formation of snow in clouds conversion of frost to water vapor

condensation of rain from water vapor

evaporation of water

a candle flame forming a cation from an atom in the gas phase

mixing sodium sulfite and bleach baking bread

rusting iron cooking an egg

burning sugar producing sugar by photosynthesis

forming ion pairs separating ion pairs


Elements

An element is a pure substance that cannot be decomposed (broken down) into simpler

substances.

Each element has been given a 1 or 2 letter symbol:

the first letter of the symbol is always a capital letter

eg, H for hydrogen, C for carbon, N for nitrogen

if there is a second letter in the symbol it is a lower case letter

eg, He for helium, Ca for calcium, Ne for neon

Elements can be present in nature as solids, liquids or gases.

Liquid Elements Gaseous Elements Solid elements

2 elements exist in nature as liquids:

11 elements exist in nature as gases:

all other elements exist in nature as solids, eg:

mercury (Hg) bromine (Br)

hydrogen (H) helium (He) nitrogen (N) oxygen (O) fluorine (F) neon (Ne) chlorine (Cl) argon (Ar) krypton (Kr) xenon (Xe) radon (Rn)

lithium (Li) carbon (C) sodium (Na) magnesium (Mg) aluminium (Al) silicon (Si) phosphorus (P) sulfur (S) potassium (K) calcium (Ca) zinc (Zn)

The atmosphere is mostly made up of the elements nitrogen (~78%) and oxygen (~21%).

Common elements found in the earth's crust are:

oxygen (O) silicon (Si) aluminium (Al) iron (Fe) calcium (Ca) sodium (Na) potassium (K) magnesium (Mg) hydrogen (H)

The most common elements found in living things are:

carbon (C) hydrogen (H) oxygen (O) nitrogen (N) phosphorus (P) sulfur (S)


The most common elements found in the universe are:

hydrogen (H) helium (He) oxygen (O) carbon (C)

Compounds

Compounds are pure substances made up of 2 or more elements.

Each compound has a formula showing which elements are present in the compound

Examples of some common compounds are shown below.

compound

name

compound

formula elements present

water H2O hydrogen (H) and oxygen (O)

ammonia NH3 nitrogen (N) and hydrogen (H)

carbon monoxide CO carbon (C) and oxygen (O)

carbon dioxide CO2 carbon (C) and oxygen (O)

sodium chloride NaCl sodium (Na) and chlorine (Cl)

sodium hydroxide NaOH sodium (Na), oxygen (O) and hydrogen

(H)

calcium chloride CaCl2 calcium (Ca) and chlorine (Cl)

calcium carbonate CaCO3 calcium (Ca), carbon (C) and oxygen (O)

calcium nitrate Ca(NO3)2 calcium (Ca), nitrogen (N) and oxygen (O)

calcium

phosphate Ca3(PO4)2

calcium (Ca), phosphorus (P) and oxygen

(O)

calcium sulfate CaSO4 calcium (Ca), sulfur (S) and oxygen (O)

methane CH4 carbon (C) and hyrogen (H)

ethanol C2H5OH carbon (C), hydrogen (H) and oxygen (O)


A compound can be decomposed into simpler pure substances.

For example, an electric current can be passed through water to form the elements hydrogen and oxygen.

Water can be decomposed into hydrogen and oxygen. Water is a compound made up of hydrogen and oxygen.

Types of mixtures

Homogeneous Solution

Homogeneous solution can be defined as that mixture which is formed by the combination of a

solute in solvent, which cannot be seen as separate entities either by naked eye or through

microscope or ultra-microscope.

A homogeneous solution cannot be separated by physical separation, simple filtration or

even by ultra-filtration.

Air around us is the most common example of homogeneous mixture. Air is composed of many

individual elements like oxygen, nitrogen, hydrogen, ozone and noble gases, compound gases like

carbon di oxide, nitrogen oxides, oxides of sulfur and water vapor.


Heterogeneous Solution

Heterogeneous solution is the one in which the solute and solvent particles are seen either by

naked eye or by microscope and can be separated by the normal filtration or ultra-filtration.

Heterogeneous solutions are not transparent and they are either translucent or sometimes opaque.

Homogeneous Vs Heterogeneous

Homogeneous solution Heterogeneous solution

Clear solution. Transparent and will not settle Translucent or opaque solution may settle in

some cases

Solutes and solvent cannot be separated by

filtration

Can be separated by filtration, or

semipermeable membrane

Light passes through the solution without any

obstruction

Light is blocked or refracted when passed

through the solution

Individual components can be separated only by

fractional crystallization or distillation

Individual components can be separated by

physical methods or by filtration

Salt water, air, alloys are examples of

homogeneous solutions

Smoke, milk, muddy water are examples of

heterogeneous solutions

Solutions: Solution is defined as a homogeneous mixture of two or more components.

Solute : It is that component of the solution, which is present in the smaller amount by weight in the

solution.

Solvent : It is that component of the solution, which is present in the larger amount by weight in the

solution. A solvent may be a liquid, solid, or gaseous substance that dissolves another solid, liquid,

or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent.

For e.g. In the figure shown below, some sugar is added in the water .So, solute is

sugar and solvent is water here.


Suspensions (heterogeneous):

A suspension is a mixture between a liquid and particles of a solid. In this case the particles do not

dissolve. The particles and the liquid are mixed up so that the particles are dispersed throughout the

liquid. They are "suspended" in the liquid. A key characteristic of a suspension is that the solid

particles will settle and separate over time if left alone. An example of a suspension is a mixture of

water and sand. When mixed up, the sand will disperse throughout the water. If left alone, the sand

will settle to the bottom.

Colloids (heterogeneous):

A colloid is a mixture where very small particles of one substance are evenly distributed throughout

another substance. They appear very similar to solutions, but the particles are suspended in the

solution rather than fully dissolved. The difference between a colloid and a suspension is that the

particles will not settle to the bottom over a period of time, they will stay suspended or float. An

example of a colloid is milk. Milk is a mixture of liquid butterfat globules dispersed and suspended in

water. Colloids are generally considered heterogeneous mixtures, but have some qualities of

homogeneous mixtures as well.

Emulsion:

In physical chemistry, mixture of two or more liquids in which one is present as droplets, of microscopic or

ultramicroscopic size, distributed throughout the other.

Properties of Matter

Some common examples of physical properties of matter are:

Physical state

Colour

Odour

Solubility in water

Hardness

Boiling point

Melting point

Density

Some common examples of chemical properties of matter are:

Iron rusts in moist air

Nitrogen does not burn

Gold does not rust

Sodium reacts with water

Silver does not react with water

Water can be decomposed by an electric current.

http://global.britannica.com/science/physical-chemistry

http://global.britannica.com/science/mixture

http://global.britannica.com/science/liquid-state-of-matter

kuala lumpur, malaysia formative assessment: i 7-understanding matter_… · the atomic theory of...

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