Chemistry 2

Acid-Base indicator: A substance that changes color when exposed to either an acid or base.

PH : A measure of the concentration of hydrogen (H+) ions in a solution. Acidic solutions have a pH less than 7. Basic solutions have a pH greater than 7. A neutral solution has a pH of 7.

Adjusting-PH-Levels

 

How to determine the pH of a solution ? 

To calculate the pH of the aqueous solution, you need to know the concentration of hydronium ions (in moles per liter (molar concentration)) The pH was then calculated using the following expression: pH = -log [H3O +]

 

chemistry

Bohr’s theory can be used for the single electron in the hydrogen atom. The energy levels are more complex if there are additional electrons. When many electrons are present, some are easier to remove from the atom than others. The most outside electrons (the two highest energy electrons) are easiest to remove. The energy required to remove them are called the first and second ionization energies.

If a large amount of energy id needed to remove an electron from an atom, the arrangement of electrons in that atom is considered to be especially stable.

The second electron to be removed from the nucleus is more tightly bound. This is because of a greater electrostatic attraction to the positively charged nucleus. Therefore, it makes more energy to remove this electron. The second ionization energy is always higher than the first.

The size of atomic radius correlates with their ionization energies. In the periodic table, as you go from left to right across a row, the atomic radius of the elements become smaller. In the same way, as you go from left to right across a row, the ionization energy of the elements increases. This is because the nuclear charge is increasing, putting a stronger electrostatic attraction on outer shell electrons. As the electrons are held more tightly you would expect the size of the atoms to decrease.

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When elements are arranged properties to their atomic numbers a pattern emerges in witch similar properties occur regularly. This is the periodic law.

Period is a horizontal row of elements in the periodic table.

Chemical group is a family of elements in the periodic table that have similar electron configurations and properties.

 

Checking up

 

  1. What is an ion?

        Atoms that have lost or gained electrons are called ions.

  1. What is ionization energy?

        The amount of energy needed to remove an electron from an atom.

  1. Explain the term chemical group.

        Chemical group is a family of elements in the periodic table that have similar electron configurations and properties.

  1. Name three elements in a chemical group

        Zinc, Cadmium and Mercury.

  1. Provide the complete electron configuration for the atom argon (Ar).

        The electron configuration for Argon is 1s22s22p63s23p6

Section 7

Polymers : Natural and Synthetic

In this lab, we measure 50 mL of polyvinyl alcohol (PVA) solution into 250 mL beaker mix with 10 mL of sodium tetra borate. And our group choose Blue. And it has more viscosity. When you pull very quick it break but if you pull vey slow, it will move very slow. Because the bonds become stronger.

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Checking Up

  1. Describe polymers and polymerisation in your own words. Answer : (1) Polymerisation is the chemical unit process of combining one or several substances with simple small molecules into substances having a large molecular weight.(2) Polymers are made up of many molecules all strung together to form really long chains.
  2. Name two naturally occurring polymers. Answer : (1) nylon and (2) polyethylene
  3. Give examples of five polymers that are manufactured using technological processes. Answer : (1) Polyvinyl Chloride, (2) Plexiglas, (3) Teflon, (4) natural rubber and (5) Nylon

Section 6

Properties of Metals and Nonmetals

A Metal : (Gold, silver, iron, copper, etc.)

  1. opaque 
  2. shiny
  3. good electrical conductivity
  4. good thermal conductivity

A Nonmetal : (Oxygen, Hydrogen, Nitrogen, Argon, etc.)

  1. highly volatile
  2. low elasticity
  3. good insulators of heat
  4. good insulators of electricity

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Checking Up

  1. List five properties of metals and five properties of nonmetals. Answer : (2) Gold, Silver, Iron, Zinc and Aluminium. (2) carbon, oxygen, hydrogen, chlorine and neon.
  2. Why is it important to prevent the oxidation of metals used in construction? Answer : Most metal oxides are much weaker and easier broken. These make the structure potentially dangerous to collapse.
  3. What is a metalloid? Answer : Metalloids share some characteristics of metals and some nonmetals. Metalloids are solids. They can be either shiny or dull.
  4. Explain the meaning of an alloy. Answer: Alloys are materials that contain more than one metal element and still maintain the characteristic properties of metals. It also is harder and will hold its shape.
  5. Why are alloys used? Answer :Alloys mix metals with other elements to help harden and otherwise make them more useful.

Section 5

Density

It is the degree of compactness of a substance.

  • Density (D) = Mass (m) / Volume (V)
  • Mass (m) = Density (D) x Volume (V)
  • Volume (V) = Mass (m) / Density (D)

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In the Lab we did on Section 5, We need to know Density of water.

  1. We need to measure the mass of graduated cylinder (g) 
  2. We put 10mL, 20mL, 30mL, etc, into the graduated cylinder.
  3. And we need to measure the mass of graduated cylinder and water.
  4. Mass of graduated cylinder and water-Mass of graduated cylinder.
  5. After 1~4 we find the mass of water
  6. We put our number into the formula ( Density = Mass / Volume)
  7. We did the same way when we using ethanol 

We did other lab about Density

We put pen cap into water, ethanol, and their mixture. We know that if we put pen cap into different density of liquid. It will has different reaction.

  1. We put pen cap into water, and it stay on water’s surface because the density of pen cap is lower than water 
  2. We put pen cap into ethanol, and it stay at the bottom because the density of pen cap is higher than ethanol.
  3. We put pen cap into their mixture, and it stay in the middle of liquid because the density of water and the density of ethanol are balance.

m1u2-fig2-04-comparing_density2

Section 4

Physical Properties

In Section 4, we use:

  1. 1 cup flout
  2. 1/2 cup salt 
  3. 2 tablespoons cooking oil
  4. 2 tablespoons cream of tartar 
  5. 1 cup water

We make 2 balls, one is regular and the other we put send inside the ball. In this Lab, we need to know their Uniformity, Strength, Elasticity, Bounce and Malleability.

We name regular ball is Ball.1 and the ball we put send is Ball.2

  • Ball.1’s uniformity is smooth than Ball.2’s uniformity(we touch it)
  • Ball.1’s strength is better than Ball.2’s uniformity.
  • Ball.1’s elasticity is better than Ball.2’s elasticity(we use ruler)
  • Ball.1’s bounce is more than Ball.2’s bounce(we use slow motion)
  • Ball.1’s malleability is stranger than Ball.2’s malleability(we pull each ball)

Composite Materials

  1. A “composite” is when two or more different materials are combined together to create a superior and unique material. This is an extremely broad definition that holds true for all composites.
  2. A composite material is made by combining two or more materials – often ones that have very different properties. The two materials work together to give the composite unique properties. However, within the composite you can easily tell the different materials apart as they do not dissolve or blend into each other.

Section 3

 

Classifying Mixtures

In the Lab, we use different kinds of materials mixed with water, and they all have many different reaction.

matterclassify-2

  • Pure Substances-> it contains only one kind of particle throughout.

Example-> sugar, Sulfur, diamond, water, table salt and baking soda 

  • Mixture-> it contains at least two pure substances. 

Example-> water or sand and iron filings, a conglomerate rock, water and oil, a portion salad, trail mix, and concrete.

  • Tyndall effect->The Tyndall effect is the scattering of light as it passes through the colloid. A single suspended particle scatters and reflects light such that the beam is visible.

    The amount of scattering depends on the frequency of light and the density of the particles. Like Rayleigh scattering, blue light is stronger than red light by the Tindel effect. Another way to observe it is to transmit longer wavelengths of light while shorter wavelengths of light are reflected by scattering.

Section 2

Water has three types of changes: solid (ice), liquid (water) and gas (water vapor). These three changes are called “three-state changes”

phase-change-diagram

In our life, all humans need to drink water everyday. When the weather is very hot, we eat ice or ice cream. We use water to shower, make cup noodle and clean the house, etc. 

Example:

Water vapor -> The use of water vapor to promote things: the water heated, will continue to produce water vapor, the use of steam power can make the windmill turning, steam can be used more to promote more great things, such as: Watt invented the steam train.

Water vapor of gas:                                                                                   There is no certain shape and size, invisible and intangible.

Ice -> Production Popsicle: water will form a cold ice, so you can add a variety of things in the water to ice, made of delicious popsicles or other ice class things.

Solid ice:
Have a certain shape and size, visible also tangible

Water -> Distilled sea water: no fresh water in the sea to drink, the water can be the first evaporation, and then collect water vapor, the water vapor after cooling without salty taste, you can quench their thirst.

Liquid water:
There is no certain shape, but a certain volume, shape, with the container to change the different, visible also tangible, will wet hands.

 

In this section, we talk about temperature. We use temperature to do lots of things. I heard a experiment before, first thing you need to put your hands into a 45~50 degrees C’s water. 3 minutes later, put your hands into a  30 degrees C’s water. Your hands will feel colder. Conversely, you put your hands into 15 degrees C’s water. 3 minutes later, put your hands into a 30 degrees C’s water. Your hands will feel really hot.

Melting and Boiling points ->

“Solid” -> melting -> “Liquid” -> Boiling -> “Gas”

phasechanges

Source of information( picture ) :

http://www.chemistry.wustl.edu/~edudev/LabTutorials/Thermochem/Fridge.html

http://physics.tutorvista.com/thermodynamics/phase-change.html

Section 1

There are three type of water, liquid, solid and gas. We drink water everyday, but sometime we not really know what is water’s components.

H2 + O -> H2O

H2O + energy -> H2 + O2

H2 (Hydrogen) is a element also a molecule 

O  (oxygen) is a element 

H2O (water) is a molecule also compound 

Chemistry world is very cool and interesting, because there are many you    don’t know and have never seen before. There are many elements in the world. For example, C is carbon and O is oxygen. So, they can become CO2. It is carbon dioxide. Na(sodium) is a element and Cl(chlorine) is a element. You combine them and become NaCl(Sodium Chlorine, salt). It is pretty weird because you put this two element together and they become the salt that we eat everyday. The world is very magical and amazing because you do not know what is happen next. So, everything you need to try and experiment.

Na + Cl -> NaCl

Element, molecule and compound are different. Element is like H, O, C, Br, Cl and S, etc. Many elements is single atoms. There are 7 elements that exist in diatomic form. They are H2, O2, N2, F2, Cl2, Br2 and I2. Molecule is very special thing because it is a group of atoms bonded together. Like H2, O2 and Br2 they can be molecule. Also H2O, CO2, CaCO3 and NaCl. Compound  is a thing composed of two or more separate elements; a mixture.

In this section we know the thing call conservation of mass. The law of conservation of mass states that mass of an isolated system is neither created nor destroyed by chemical reactions or physical transformation rule. According to the law of conservation of mass, the quality of the chemical reaction in the product must be equal to the mass of the reactant.

H2O + energy -> H2 + O2 become 2H2O + energy -> 2H2 + H2

HCl + Zn -> ZnCl2 + H2   become  2HCl + Zn -> ZnCl + H2 

Fe2O3 + CO -> CO2 + Fe become Fe2O3 + 3CO -> 3CO2 + 2Fe

  1. Can all compounds be decomposed into their elements?                           Yes, all compounds can be decomposed into their elements.
  2. what techniques can be used to decompose compounds?            Techniques can be used to decompose compounds. For example, electrolysis, Magnetization and Filtering, etc.                        
  3. What are elements made of?                                                                            Element is a substance made entirely from one type of atom.
  4. what are atoms?                                                                                               the basic unit of a chemical element.
  5. what are molecules?                                                                                           A group of atoms bond together, represent the minimum basic unit can participate in a chemical reaction chemical compounds