Does it Matter?(Yr 7 Unit 1)

Chapters 1 & 3 – Science Tracks

Particle Theory of Matter

The Particle Theory of Matter implies that all things are made of matter and matter is made up of particles too small to see. Matter has mass and takes up space (volume).

Everything on Earth, everything in our solar system, everything in our galaxy, and everything in the universe is made up of matter. Matter is the name scientists have given to everything that you can touch, or see, or feel, or smell.

What are atoms? DP 1 & 2

Atoms are the basic building blocks of matter

Matter is a substance that has mass and occupies space

Atoms are the smallest indivisible unit of matter (atoms are too small to see)

A desk, air, even you are made up of atoms

Atoms DP 3

Atoms are made up of three basic particles:

1. Protons – carry a positive charge2. Neutrons – carry a neutral charge3. Electrons – carry a negative charge

Protons, neutrons and electrons are known as ‘subatomic particles’

Read ‘Info Box’ on p.79 of your text

Atoms DP 3 cont-

The central core of the atom is called the nucleus it contains the protons and neutrons

The nucleus is surrounded by an electron cloud

Draw and Label a diagram of the ATOM

Draw an Atom DP 3 cont-

See p. 79 of your text

Helium atom

What are Molecules? DP 4

A molecule consists of two or more atoms of the same element, or different elements, that are chemically bound together.

Safety Labels DP 7

Toxic

Explosive

?

More about Matter

Matter can be divided into three groups:

Solids Liquids Gases

These groups are based on the arrangement (i.e. how they are packed together) and motion of the

atoms. Solids, liquids and gases are ‘states of matter’

Properties of Gases, Liquids and Solids

GAS LIQUID SOLID

assumes the shape and volume of its containerparticles can move past one another

assumes the shape of the part of the container which it occupiesparticles can move/slide past one another

retains a fixed volume and shape rigid - particles locked into place

compressible lots of free space between

particles

not easily compressiblelittle free space between particles

not easily compressibleAlmost no free space

between particles

flows easilyparticles can move past one another

flows easilyparticles can move/slide

past one another

does not flow easilyrigid - particles cannot move/slide past one another

  Solids Liquids Gases

Similarities All are made of particles

  All can be pure substances or mixtures

Differences Particles in fixed positions about which they vibrate

Particles are free to roll over each other

Particles are in rapid movement in all directions

  Fixed shape Fill the bottom of the container holding them

Fill all the space provided

Solid Liquid Gas

sand kerosene nitrogen

carbon milk ozone

chalk alcohol neon

plastic mercury chlorine

sawdust    

flour    

copper    

Link – Gases, Liquids and Solids

http://www.chem.purdue.edu/gchelp/atoms/states.html

http://www.harcourtschool.com/activity/states_of_matter/

Structure of Gases, liquids and Solids

Particles (elements) in a: gas are well separated with no regular arrangement. liquid are close together with no regular arrangement. solid are tightly packed, usually in a regular pattern.

Particles (elements) in a: gas vibrate and move freely at high speeds. liquid vibrate, move about, and slide past each other. solid vibrate (jiggle) but generally do not move from place to place.

Liquids and solids are often referred to as condensed phases because the particles are very close together

Elements, compounds and mixturesElements: consist of only one kind of atom, cannot be broken down into a simpler type of matter by either physical or chemical

means, and can exist as either atoms or molecules

Compounds: consist of atoms of two or more different elements bound together, can be broken down into a simpler type of matter (elements) by chemical means (but not

by physical means), has properties that are different from its component elements There are two types of compounds – molecular and ionic (see next slide)

Mixtures: consist of two or more different elements and/or compounds physically intermingled, can be separated into its components by physical means, and often retains many of the properties of its components.

Compounds

Molecular compounds – are formed from molecules and can be either solid, liquid or gas at room temp.

Ionic compounds – are formed by ions, they are solid at room temp. Commonly known as salts.

Note: Ions are atoms with either extra electrons or missing electrons

Link - Elements, compounds and mixtures http://www.chem.purdue.edu/gchelp/

atoms/elements.html

The Periodic Table As you probably saw, the periodic table is organized like a big grid. The ELEMENTS are

placed in specific places because of the way they look and act.

In the periodic table, elements have something in common if they are in the same row.

Every element in the top row (the first period) has one shell for its electrons. All of the elements in the second row (the second period) have two shells for their electrons. It goes down the periodic table like that. At this time, the maximum number of shells is seven. Each of the rows are considered to be different PERIODS.

When a column goes from top to bottom, it's called a GROUP. The elements in a group have the same number of electrons in their outer shell.

Every element in the first column (group one) has one electron is its outer shell. Every element on the second column (group two) has two electrons in the outer shell. As you keep counting the columns and you'll know how many electrons are in the outer shell.

Concept Map – ‘Matter’The periodic table has been published in various shapes and sizes, but the most commonly used modern form begins with a column of group 1 metals on the left-hand side, followed by a column of group 2 alkaline earth metals. These columns are followed by a block of 40 elements divided into ten columns of four elements each. The groups in this block, collectively called the transition metals, are numbered 3 through 12. Groups 13 through 18 make up the right-hand side of the table. A diagonal dividing line separates the nonmetals in the upper-right portion of this block, such as oxygen, carbon, and nitrogen, from the metals such as tin and lead in the lower left portion.

The elements in between, with the grey color, are called TRANSITION elements. They have special electron rules.

                                                               

                                                      

Reading the Periodic table

Reading the Periodic Table cont-

In an atom, the electrons spin around the center, also called the NUCLEUS. The electrons like to be in separate SHELLS. Shell number one can only hold 2 electrons, shell two can hold 8, and for the first eighteen elements shell three can hold a maximum of eight electrons. Once one shell is full, the next electron that is added has to move to the next shell.

So... for the element of BERYLLIUM, you already know that the ATOMIC NUMBER tells you the number of electrons. That means there are 4 electrons in a beryllium atom. Looking

at the picture, you can see there are two electrons in shell one and two in shell two.

WHAT HAPPENS WHEN ELEMENTS COMBINE?

When several elements come together it is called a COMPOUND. Compounds can be made up of two atoms or hundreds of atoms. There are even compounds that have the same number of atoms but have different shapes. These compounds with different shapes are called ISOMERS.

No matter what atoms are in a compound, they all want to be "happy". A happy atom is one with the right number of ELECTRONS in the outer ORBITAL. That desire to be happy is why some elements only combine with a few other elements. Not all elements can make each other "happy".

Chemical Reactions

In chemistry, a reaction is when two or more molecules interact and something happens.

chemical reaction, process by which one or more substances may be transformed into one or more new substances. Energy is released or is absorbed, but no loss in total molecular weight occurs.

  The more particles that there are, the more will collide per

second, and so the rate of the reaction increases.

 

Rate of reaction

The RATE of a reaction is the SPEED at which a reaction happens. If a reaction has a low rate that means the molecules combine at a slower speed than a reaction with a high rate. Some reactions take hundreds, maybe even thousands of years while other can happen in less than one second. The rate of reaction depends on the type of molecules which are combining.

COLLISION THEORY. The collision theory says that the more collisions in a system, the more likely combinations of molecules will happen. So if there are a higher number of collisions in a system... More combinations of molecules will occur, the reaction will go faster, and the rate of that reaction will be higher.

FORCES THAT CHANGE THE SPEED OF REACTIONS

Reactions happen, no matter what. Chemicals are always combining or breaking down. Over and over again but not always at the same speed. There are a few things which really affect the speed of the reaction and the number of collisions that can occur.

(1) CONCENTRATION: If there is more of a substance in a system there is a higher chance that molecules will collide and speed up the rate of the reaction.

(2) TEMPERATURE: When you raise the temperature of a system the molecules bounce around a lot more (because they have more energy). When they bounce around more they are more likely to collide. That means they are also more likely to combine.

(3) PRESSURE: Pressure effects the rate of reaction especially when you look at gases. When you increase the pressure the molecules have less space to move around. That greater concentration makes them collide with each other more often.

Reaction rate is affected by these four things:

Concentration: an increase in concentration means there are more particles. More particles means there will be more collisions. This should increase the reaction rate.

Surface area: when one of the reactants is a solid, the reaction can only take place at the surface of the solid. Breaking the solid into smaller pieces will increase the surface area exposed to the other reactant. This should increases the reaction rate.

Temperature: since temperature is a measure of the motion of particles, increasing the temperature will cause the particles to move faster. When particles move faster, more collisions occur and the collisions are more violent. This should increase the reaction rate.

Catalysts: catalysts are substances that change the rate of a chemical reaction without being changed in the reaction. Catalysts are most often used to speed up a chemical reaction. They do this by changing the steps needed between the reactants and the formation of the products. If the number of steps can be reduced, the reaction rate should increase.

This is Sodium chloride, also known as table salt. The formula for salt is NaCl. One Sodium atom gives it's electron to one chlorine atom. Chlorine then has the eight electrons in its outer shell to make it "happy". Sodium is "happy" because it has now given up its one extra electron.

                                                     

                                 

                                          

Sodium Oxide. When sodium atoms bond with one oxygen atom there have to be two sodium atoms, each with an extra electron. Each of these Sodium atoms gives oxygen one electron, allowing Oxygen to have a full shell with eight electrons. See how the electrons are shared?

                                                                                                                                                                           

Figure 3.14 Particles of common substances. (Problem Solving 3.1 p87)Attempt questions 2a, 2c, 2d, 2e, 2f

Hydrogen H (Atomic No 1)

Hydrogen is the lightest element. It is by far the most abundant element in the universe and makes up about about 90% of the universe by weight. Hydrogen as water (H2O) is absolutely essential to life and it is present in all

organic compounds. Hydrogen gas was used in lighter-than-air balloons for transport but is far too dangerous because of the fire risk (Hindenburg).

The lifting agent for the ill fated Hindenberg ballooon was hydrogen rather than the safer helium.

Helium He (Atomic No 2)

Helium is one of the so-called noble gases. Helium gas is unreactive, colourless, and odourless. Helium is available in pressurised tanks.

Elemental helium is a colourless odourless monoatomic gas. Helium is the second most abundant element in the universe after hydrogen. particles are doubly ionised helium atoms, He2+.

Helium is used in lighter than air balloons and while heavier than hydrogen, is far safer since helium does not burn. Speaking after breathing an atmosphere rich in helium results in a squeaky voice (don't try it!).

Carbon C (Atomic No 6)

Carbon is found free in nature in three allotropic forms: amorphous, graphite, and diamond. Graphite is one of the softest known materials while diamond is one of the hardest. Carbon, as microscopic diamonds, is found in some meteorites. Natural diamonds are found in ancient volcanic "pipes" such as found in South Africa. Diamonds are also recovered from the ocean floor off the Cape of Good Hope.

Carbon is present as carbon dioxide in the atmosphere and dissolved in all natural waters. It is a component of rocks as carbonates of calcium (limestone), magnesium, and iron. Coal, petroleum, and natural gas are chiefly hydrocarbons. Carbon is unique among the elements in the vast number of variety of compounds it can form.

Nitrogen N (Atoms No 7)

Nitrogen makes up about 78% of the atmosphere by volume but the atmosphere of Mars contains less than 3% nitrogen. Its compounds are vital components of foods, fertilizers, and explosives. Nitrogen gas is colourless, odourless, and generally inert. As a liquid it is also colourless and odourless.

When nitrogen is heated, it combines directly with magnesium, lithium, or calcium. When mixed with oxygen and subjected to electric sparks, it forms nitric oxide (NO) and then the dioxide (NO2). When

heated under pressure with hydrogen in the presence of a suitable catalyst , ammonia forms (Haber process). Nitrogen is "fixed" from the atmosphere by bacteria in the roots of certain plants such as clover. Hence the usefulness of clover in crop rotation.

Oxygen O While about one fifth of the atmosphere is oxygen gas, the

atmosphere of Mars contains only about 0.15% oxygen. Oxygen is the third most abundant element found in the sun, and it plays a part in the carbon-nitrogen cycle. Oxygen in excited states is responsible for the bright red and yellow-green colours of the aurora. About two thirds of the human body, and nine tenths of water, is oxygen. The gas is colourless, odourless, and tasteless. Liquid and solid oxygen are pale blue (see picture above) and strongly paramagnetic (contains unpaired electrons).

More about Oxygen O Ozone (O3) is another allotrope of oxygen. It is formed from electrical

discharges or ultraviolet light acting on O2. It is an important

component of the atmosphere (in total amounting to the equivalent of a layer about 3 mm thick at ordinary pressures and temperatures) which is vital in preventing harmful ultraviolet rays of the sun from reaching the earth's surface. Aerosols in the atmosphere have a detrimental effect on the ozone layer. Large holes in the ozone layer are forming over the polar regions and these are increasing in size annually. Paradoxically, ozone is toxic! Undiluted ozone is bluish in colour. Liquid ozone is bluish-black, and solid ozone is violet-black.

Oxygen is very reactive and oxides of most elements are known. It is essential for respiration of all plants and animals and for most types of combustion.