Ultimate notes

Science

1. Acid and Alkalis

2.Solutions

3. Separations techniques

4. Chemical Definitions

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Acids: Properties of Acids

1. Acids are sour
2. Acids turn blue litmus paper red
3. Acids react with metals to give off hydrogen gas
4. Acids react with metal carbonates to give off carbon dioxide gas
5. Acids vary in type

SOUR ACIDS

Lemons have citric acid, that’s why they are sour. Acids are sour. “Why” is not tested. So don’t ask so much.

TURNING BLUE TO RED

(No form of explanation)

HYDROGEN GAS

When dilute sulphuric or hydrochloric acid reacts with metals (magnesium strips etc), the gas produced is Hydrogen gas. When a lighted splint is hovered over the reaction of the acid and metal, a pop sound would be heard and the flame would be extinguished.

CARBONATE TO CARBON DIOXIDE

When an acid reacts with any metal carbonate (calcium carbonate), the gas produced is carbon dioxide.

For example when Calcium Carbonate reacts with dilute hydrochloric acid:

Calcium Carbonate + dilute hydrochloric acid= calcium chloride + carbon dioxide + water

TYPES OF ACIDS

Mineral acids

· Solutions of hydrogen halides, such as hydrochloric acid and hydrobromic acid

· Sulfuric acid

· Nitric acid

· Phosphoric acid

· Chromic acid

Sulfonic acids

· Methanesulfonic acid

· Ethanesulfonic acid

· Benzenesulfonic acid

· Toluenesulfonic acid

Carboxylic acids

· Formic acid

· Acetic acid

· Citric acid

Alkali: Properties of Alkalis

1. Bitter in taste

2. Turns (moist) litmus paper blue

TESTING...

You can test for a alkali by adding ammonia sulphate. Then heat it gently, and test with moist red litmus paper.

Neutralization

A reaction called “neutralization” occurs when you mix an acid and an alkali.

For example: alkali + acid = salt + water

sodium hydroxide + hydrochloric acid = sodium chloride + water

PH level

In a retarded nut shell, if you increase the pH of a acid/neutral/alkali it gets more alkaline. When pH is lowered, the substance becomes more acidic instead. To test the pH, there are around 4 indicators like Litmus paper. Substances like vinegar can be added to lower/increase pH.

Solutions

Analogy: Sugar + Water = Sugar Solution

We say that sugar is soluble in water. The mixture of sugar and water is called a solution.

What makes up a Solution?

Solute + Solvent = Solution

A solute is the substance that dissolves in a liquid. (Sugar etc)

A solvent is the liquid that dissolves other substances. (Water etc)

A solution is the result when a solute dissolves into a solvent. (Sugar water etc)

Properties of a solution

1. Solutions are always clear or transparent
2. Solutions are always colored or colorless
3. A solution is Homogenous.

v Mixtures are not Homogenous

v Solutions are. (When the result looks like the result on the spoon, the result is Homogenous)

4. If we leave a solution to stand, the solute, will not settle to the London.
5. The solute particles in a solution can pass through the filter paper.
   
   

Factors that solubility

1. Type of solute
1. For example, the solubility of sugar is higher than that of salt
2. Type of solvent
3. Temperature

(Stub)

Separation techniques

1. Filtration
2. Crystallization
3. Distillation
4. Fractional Distillation

Filtration

Purpose: To separate an insoluble solid from a liquid (insoluble solid: Chalk powder in water)

Example: To obtain sand from seawater

To obtain chalk powder from water

Crystallization

Purpose: To obtain solid from its solution. Solid decomposes on strong heating.

Example: To obtain sugar crystal from sugar solution. To obtain copper (II) sulphate crystals from copper (II) sulphate solution.

Distillation

Purpose: To obtain a pure liquid from a solution.

Example: To obtain pure water from sea water.

Fractional Distillation

Purpose: To separate miscible liquids with different boiling points.

Miscible: Definition- Liquids that are soluble in one another.

Example: To separate mixtures like air or petroleum into their separate components.

Some notes:

v The fractionating column separates the components in the mixture according to the boiling points.

v The liquid with the lowest boiling point distils out first.

v The liquid with the highest boiling point distils out last.

CHEM definitions

Elements-

An element is a substance that cannot be broken down to simpler substances by chemical reaction

Or

An element is a substance that contains of only one single type of atom

(Chlorine/Carbon/Nitrogen are all examples of elements)

Compound-

A compound is a substance containing two or more elements joined together by a chemical reaction (Mostly involving HEAT LIGHT or ELECTRICITY).

(WATER/SALT/CHALK are all examples of elements as they all have more than two elements conjoined)

(Water= Hydrogen + Oxygen)(Salt= Sodium + Chlorine)

Properties of compounds:

1. Each compound always contains the same elements in a fixed proportion/ratio by mass
2. Compounds cannot be separated into elements by physical methods.
3. Compounds can be separated into its individual elements by chemical reaction.
4. In a compound, atoms will combine to form molecules

Sub atomic particles-

There are 3 sub atomic particles that make up each atom: Protons, Electrons and Neutrons.

Mixtures-

A mixture consists of two or more elements and/or compounds which are not joined chemically.

3 cases of mixtures: Mixture of elements, mixture of compounds, mixture of both compounds and elements.

Properties of Mixtures

1. The substance in a mixture does not have a fixed composition.
2. A mixture does not have a fixed melting and boiling point
3. When a mixture is formed no chemical reaction takes place
4. A mixture can be separated back easily into its component substances by physical methods like the mentioned Filtration, Crystallization and Distillation.

Solutions-

Read page 3 (idiot)