Lifestyle Chemistry Intro

Year 10 Science - Topic One !

Lifestyle Chemistry

What is this topic about?Often without realising it, you are exposed to chemistry in your everyday

lives. This topic introduces you to the chemistry that is involved in the cosmetic and jewellery industries. It examines the sorts of chemicals we

put on our skin and how the skin reacts to these treatments. !

As long as there is recorded human history, adornment of the body with jewellery has been a part of human culture. What materials have been

used and why? Could we improve on these?

Learning Intensions…The key focus ideas for this topic are…

What are Atoms?Atoms are small particles that that make up everything around us (matter). The

are invisible to the naked eye, but you can use a very powerful electron scanning microscope.

The atoms above have been magnified 45 million times!

Elements, like gold and oxygen, are pure substances made up of only one type of atom.

The structure of AtomsThere are over 100 different atoms in our world, but they all have the same

basic structure.

An atom is very similar to the solar system in structure. The largest chunk of the atom is in the centre, and is called

the nucleus. !

Smaller particles whiz around the outside at incredible speeds. They move so fast

that atoms appear to be solid, even though they are mostly empty space.

Atoms are made up of even smaller particles, called protons (p+), neutrons (n) and electrons (e-)

Neutrons

The structure of Atoms

Protons

Electrons

are positively charged, and located in the nucleus.

have no charge, and are also located in the nucleus.

electrons have a negative charged and whiz around the outside of the nucleus.

Opposite charges attract each other, so this keeps the electrons from spinning out of the atom.

TASK: Draw a general diagram of an atom, including subatomic particles, into your workbook.

Subatomic particles are held together in the atom by electrical charges. Particles with oppositely charged particles are attracted to one another.

Protons - have a positive electrical charge Electrons - have a negative electrical charge Neutrons - have no electrical charge

An atom usually has an equal number of positively charged

protons and negatively charged electrons. This makes the atom

itself electrically neutral.

TASK: define the terms protons, electrons and neutrons your workbook. What does “electrically neutral” mean?

Atoms have the same number of positive charges (protons) and negative charges (electrons). The number of protons in an atom is called its atomic

number.

Atomic Number

The total number of particles in an atom’s nucleus is called its mass number (protons plus neutrons).

Each type of atom has its own unique symbol. All this information can be shown as below:

The picture opposite show information for an atom of

fluorine. How many protons does it have?

How many electrons does it have? How many neutrons does it have?

atomic number

number of protons

number of electrons

==

mass number

number of protons

number of neutrons

+=

TASK: answer the following questions on “Atomic Number” in your workbook.

1. Define the term “Atomic Number”. !2. State the atomic number for the following elements

Platinum Gold Oxygen Magnesium Californium Bromine Krypton !

3. State the name for atoms with the following atomic numbers 6 3 40 13 92 56 1

TASK: answer the following questions about “Mass Number” in your workbook.

1. Define the term “Mass Number”. !2. State the mass number for the following elements

Helium Silver Carbon Iron Caesium Lead Samarium !

3. State the name for atoms with the following mass numbers 16 122 45 27 79 23 9

Most atoms exist in a number of different forms, called isotopes. Each form has the same number of protons and electrons, but a different number of

neutrons. So all the isotopes of an atom have the same atomic number, but they have different mass numbers.

!The mass number of an atom is written beside its

name. For instance, carbon-12 has six protons and six neutrons, and a mass of 12.

Isotopes

In nature, some isotopes may be more common than others.

TASK: answer the following questions about ‘isotopes’ in your workbook.

1. Define the term “isotope”. !2. Identify the atomic masses of the following isotopes

- oxygen-12, oxygen-13 and oxygen-14 - helium-3 and helium-4 - barium-114 and barium-116

!3. Isotopes are often used in industry. For the following isotopes, briefly list one industrial use:

- Iodine-123 - Technetium-99

!

Most neutral atoms have several shells of electrons. The first shell can hold up to 2 electrons and the second and third shells up to eight, although some atoms can

have up to 18 electrons in their third shell. When a shell is full, the electron begins a new shell.

!The arrangement of electrons around the nucleus is called the electron configuration. This can be written in numbers next to the atom’s name.

!We can also draw diagrams to represent the electron configuration of difference

Electron Configuration

Fluorine has an atomic number of 9, and is a neutral atom, so it also has 9 electrons. It has an

electron configuration of (2, 7) - this means 2 electrons in the first shell and 7 in the second

shell.Sodium has an atomic number of 11, and is a neutral atom, so it also has 11 electrons. It has an

electron configuration of (2,8,1) - this means 2 electrons in the first shell, 8 in the second shell

and 1 in the third.

Hydrogen has an atomic number of 1, and is a neutral

atom, so it also has 1 electron. It has an electron configuration of

(1) - one electron in the first shell

TASK: Complete the following in your workbook. !Draw diagrams to represent the electron configurations of the following atoms: - Magnesium - Argon - Nitrogen - Potassium - Silicon - Sodium !You may need to use the internet to work out the electron configuration for these atoms.

Key Scientist - Atomic Structure

Niels Bohr Niels Bohr is one of the most important chemists of recent times. His contribution to Chemistry completely changed the way we see atoms and compounds, and allows us to

understand chemical reactions.

TASK: Using the internet, find the answers to the questions below, and write your findings in your workbook. When was he born? When did he die? What Nationality was he? What was his job? What contribution did he make to chemistry? Why is his contribution so important? Which element in the periodic table is named after him?

TASK: complete the following activity

Find 2 educational videos on Youtube that explain the structure of atoms. Watch each video. !You will need to assess the strengths and weaknesses of each video. - What was explained well? - What wasn’t explained well? - Did the presenters use useful analogies? - Did the video include helpful animations? - Did the video use correct scientific terminology? !For each video, write a half-page summary in your workbook. At the end of this, write a statement about which video was the most educational and informative for you. Justify your choice. !Construct your answers on a google doc and share with your teacher.

TASK: Working with your group, complete the following activity

Your task is to design a 3D model of an atom. !Firstly, you will need to design your model. This means you will need to sketch what it will look like, and decide what materials you will be using. !Once you have a list of your materials, you need to submit these to your teacher. We will try and provide you with the materials you require, so do not pick items that are expensive. For example, you can use plasticine instead of polystyrene balls. !You will then be given class time to construct your model, and we will display them around the room.

TASK: Complete the following in your workbook.

Atoms can be compared by examining their atomic structure. Working with a partner, copy and complete the following table into your workbook.

Elements are pure substances made up of only one type of atom. Elements

This bar of pure gold only contains

atoms of gold.

This pure sulfur powder only contains

atoms of sulfur.

Atoms belonging to the same element all have the same number of protons and the same atomic number. All gold atoms have an atomic number of 79. All

sulfur atoms have an atomic number of 16.

The periodic table is an arrangement of all the known elements placed in order of increasing atomic number. Each element is represented by a box containing its own unique chemical symbol, atomic number and atomic mass. New elements are added

as they are discovered.

The Periodic TableToday, scientists know of 118 different types of atoms. Only 92 of these are natural - all other elements are synthetic and made in a laboratory. These

synthetic elements are unstable and break down quickly.

The Periodic Table is arranged into rows and columns. Looking at the table you will see that is has numbered rows (called periods) and columns (groups).

Periods: Each period is numbered from 1-7. The atoms of all the elements in one period have the same number of electron shells. For example, elements in period 2 have two electron shells, and elements in period 3 have three.

Groups: Each group has a Roman numeral, from I - VIII. Elements in the same group have the same number electrons in their outer shell. This means that chemically, they behave in similar ways.

TASK: define the terms ‘Groups’ and ‘Periods’ in your workbook.

An element is a substance that contains only one type of atom. So far, approximately 115 elements have been discovered, but 90 only occur naturally on Earth. Elements can be sorted into metals, non-metals and semi metals (sometimes

called metalloids).

Types of Elements

TASK: Go to the following website. http://www.dummies.com/how-to/content/the-periodic-table-metals-

nonmetals-and-metalloids.html Copy the table below into your workbook, and complete using the

information on the website.

Substance Properties 3 Examples

Metals

Non-metals

Semi-metals

The Periodic Table - Groups with NamesSome of the groups in the periodic table have names.

Group 1 - known as Alkali metals Group 11 - known as Alkaline earth metals

Group V11 - known as halogens Group V111 - known as Noble gases

!Transition metals make up the middle block of the periodic table

TASK: Copy the table below into your workbook, and complete using the information on the website.

http://chemistry.about.com/library/weekly/blgroups.htm Scroll down to the ‘Colour key’ and click on the corresponding group for

information.

Group Properties 3 ExamplesAlkali Metals

Alkaline Earth MetalsHalogens

Noble GasesTransition metals

TASK: answer the following questions in your workbook.

1. Only eleven elements have symbols that are based on their old name or Latin name. Identify each of these elements by their symbol and name. !2. Identify 3 elements that have names related to our Sun and the planets. Write down their names and symbols. !3. Ten elements have names that honour importance scientists, who made pioneering discoveries in chemistry. Write down their names and symbols

TASK: complete the worksheet “Understanding the periodic table”. This must be completed for home learning.

Key Scientist - The Periodic Tabe

Dmitri Mendeleev

TASK: Using the internet, find the answers to the questions below, and write your findings in your workbook. - When was he born? - When did he die? - What Nationality was he? - What was his job? - What contribution did he make to chemistry? - Name two chemists who inspired his work? - Why is his contribution so important? - Which element in the periodic table is named after him?

Dmitri Mendeleev’s work in chemistry revolutionised the science. His contribution

to Chemistry allowed us to organise elements, according to their properties.

Extension QuestionsLevel 1 - Hard [knowledge extension activity] Level 2 - Challenging [application question, linked to Year 11 Chemistry syllabus]

If you are considering studying Physics or Chemistry next year, or just want a challenge, attempt the following activities.

!And if you need help, make sure you ask Ms Belshaw.

Level 1: Elements in the Earth

The outer most layer of the Earth, the crust, is mostly made up of only 5 elements. It is rare for these elements to occur alone, but some do, like gold. More often than not, they are found combined in compounds called minerals.

Minerals that contain metals are called ores.

TASK: list the 5 most common elements in the Earth’s crust and their percentage in their crust. Use the internet to help you.

Most minerals are formed when magma pushes up from deep below the Earth’s crust, cools and solidifies. The conditions in the place where magma cools

determines the types of minerals formed. !

Minerals are divided into groups according to the elements which make them up. Minerals that are made of a single element, like silver, are called native elements.

TASK: Copy the table below into your workbook, and use the internet to determine the element present in each mineral group. See if you can also find an example of a compound which falls into that particular mineral group. One

has been done for you.

Mineral Group Element Common ExampleSulphides Sulfur Sphalerite (compound of zinc and sulfur)

Arsenates

Borates

Chromates

Molybdates

Nitrates

Tungstates

Vanadates

We know that most elements have different forms of atoms that have different numbers of neutrons, but the same number of protons and electrons - these

are called isotopes. Consequently, isotopes have different atomic masses. !

Carbon-12, carbon-13 and carbon-14 have 6, 7, and 8 neutrons respectively. These atoms are 12, 13 and 14 times heavier than the hydrogen atom.

!Relative atomic mass (Ar), the mass value that appears in the Period Table, is the

average mass number of the atoms in a sample of an element, compared to hydrogen. For several elements, the relative atomic mass is close to a whole

number, and closely corresponds to the number of protons and neutrons. !

Other elements have relative atomic masses that are not whole numbers, as they consist of a mixture of their isotopes. In these cases, the relative atomic weight is determined by taking an average of each isotope present, and the

percentage present in the element.

Level 2: Relative Atomic Mass (Ar)

Let’s look at an example. !

Naturally occurring chlorine consists of about 75%

chlorine-35, which has an atomic mass of 35.0 and 25% chlorine-37, with an atomic

mass of 37.0 !

How many neutrons and protons does does chlorine-35

have? How many neutrons and

protons does chlorine-37 have? !!

We can calculate the relative atomic mass (Ar) of naturally occurring chlorine, using the

information above.

Figure 9.2 Distribution of Cl-35 and Cl-37 atoms in nature

Cl–35Cl–35

Cl–35

Cl–35Cl–35

Cl–35

Cl–35

Cl–35

Cl–35

Cl–35Cl–35

Cl–35

Cl–37

Cl–37

Cl–37

Cl–37

164 MODULE 2: Metals

Further examination of Table 9.1 indicates that many elements have relative atomic masses that are not close to whole-number values. This is because most elements in nature consist of several isotopes. For this reason, the relative atomic masses of elements are weighted averages of the relative atomic masses of the various isotopes that occur naturally.

The relative atomic mass of an element depends on the masses and proportions of each isotope present in nature. Naturally occurring copper consists of two isotopes with relative atomic masses of 63 and 65 respectively. The observed atomic mass of 63.55 indicates that copper-63 is the most abundant isotope. Although carbon and oxygen also have naturally occurring isotopes, one isotope of each element is by far the most abundant, so that their relative atomic masses are very close to whole-number values. Example 9.1 shows how the relative atomic mass of an element can be calculated given the proportions of each of its isotopes.

Example 9.1

Naturally occurring chlorine consists of about 75% chlorine-35, which has a relative atomic mass of 35.0, and 25% chlorine-37, with a relative atomic mass of 37.0. Calculate the approximate relative atomic mass of naturally occurring chlorine.

A (Cl) = 75 A (Cl 35) + 25 A (Cl 37)1r

r r000

= 75 35.0 + 25 37.0

100

=

+ 925100

2625

=

1003550

= 35.5

TASK: answer the following questions in your workbook.

1. Naturally occurring boron contains isotopes boron-10 and boron-11 in about 20% and 80% abundance. Calculate the relative atomic mass for boron. Compare this to the value in a period table. Comment on any difference. !2. Copper metal contains approximately 69% copper-63 and 31% copper-65. Calculate the relative atomic mass. !3. Naturally occurring carbon is 98.9% carbon-12 and 1.11% carbon-13. Calculate the relative atomic mass