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(Chemistry Projects) Class 12th Chemistry Projects for 2009 Exams (Paper Chromatography: Advanced Version - 2)

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Class 12th Chemistry Projects for 2009 Exams
Paper Chromatography: Advanced Version 2

Objective

The objective of this project is to use paper chromatography to analyze the leaf pigments found in three different types of plants.

 

Introduction

Matter and Mixtures

Matter makes up everything in the universe. Our body, the stars, computers, and coffee mugs are all made of matter. There are three different types of matter: solid, liquid, and gas. A solid is something that is normally hard (your bones, the floor under your feet, etc.), but it can also be powdery, like sugar or flour. Solids are substances that are rigid and have definite shapes. Liquids flow and assume the shape of their container; they are also difficult to compress (a powder can take the same shape as its container, but it is a collection of solids that are very small). Examples of liquids are milk, orange juice, water, and vegetable oil. Gases are around you all the time, but you may not be able to see them. The air we breathe is made up of a mixture of gases. The steam from boiling water is water's gaseous form. Gases can occupy all the parts of a container (they expand to fill their containers), and they are easily compressed.

Matter is often a mixture of different substances. A heterogeneous mixture is when the mixture is made up of parts that are dissimilar (sand is a heterogeneous mixture). Homogeneous mixtures (also called solutions) are uniform in structure (milk is a homogeneous mixture). A sugar cube floating in water is a heterogeneous mixture, whereas sugar dissolved in water is a homogeneous mixture. You will determine whether the ink contained in a marker is a heterogeneous or homogeneous mixture, or just one compound.

In a mixture, the substance dissolved in another substance is called the solute. The substance doing the dissolving is called the solvent. If you dissolve sugar in water, the sugar is the solute and the water is the solvent.

 

Chemical Bonding

Matter is made up of small particles called atoms. Each atom is made up of smaller, positively charged particles called protons, neutral particles called neutrons, and even smaller negatively charged particles called electrons. At the center of each atom is the collection of protons and neutrons called the nucleus. Electrons spin around the nucleus in different energy levels called orbitals. Each orbital corresponds to a discrete amount of energy that the electron can have. A really excited electron with a lot of energy is further from the nucleus. In the image below, the electrons are yellow with a negative sign, the protons are green with a positive sign, and the neutrons are red with no sign. Keep in mind that this is a representation of what an atom looks like. Since atoms are so small, no one has seen a full atom before with the electrons orbiting around the nucleus.

Courtesy : Sciencebuddies.org

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