Category: Chemistry

Energy: the ability to do work

 

Every movement we make requires energy. There are six forms of energy.

Chemical Energy: energy that stores within the bonds

Mechanical Energy: energy of a moving object

Thermal Energy: energy of the motion of molecules (or heat energy)

Radiation Energy: energy of lights, electromagnetic waves

Electrical Energy: energy of the movement of electrons

Nuclear Energy: energy stored within the nucleus of an atom

In our daily life basis,  energy had converted from one form to another; because according to the laws of thermodynamics, energy cannot be created or destroyed.

 

In this image, it shows that a girl is cycling. The peddling produces thermal energy and mechanical energy. The mechanical energy is then converted into electrical energy to heat up the water. Which the boiling water then produces thermal energy.

 

Determining Bonding Types:

In this experiment, we were given three different types of substances, A, B, and C. However, we do not know the identity of each substance, therefore, we have to determine which substance is paraffin, sucrose and sodium bicarbonate based on some of their physical properties. In this lab, we tested two different characteristics, melting point and solubility, to figure out what type of bond the substance has.

Data and Analysis

 

Data Table: Melting Points
	Observations about the solid substance	Melting Order	Ionic, Covalent or Polar Covalent?	Reasoning
Substance A	melt slowly Turn brown The smell comes out	2	polar covalent	has a low melting point but not as low as those in the non-polar covalent
Substance B	nothing happen yet	3	ionic compound	it has a high melting point
Substance C	melt very quicklyturn into liquid The smell   out	1	non- polar covalent	has a low melting point

 

Data Table: Solubility in water
	Observations	Solubility	Ionic, Covalent or Polar Covalent?	Reasoning for identification
Substance A	When put in the solvent, the substance sink	Soluble	polar covalent	since water has is a polar covalent with both positive and negative charge, therefore compound that has charge (ionic and polar) would be attracted to the water molecules
Substance B	when put in the solvent, the substance sink, melt quickly, faster than sugar	Soluble	ionic compound	since water has is a polar covalent with both positive and negative charge, therefore compound that has charge (ionic and polar) would be attracted to the water molecules and easily breaks the compound bonds
Substance C	When put in the solvent, the substance float	Insoluble	non-polar covalent	non-polar compound doesn’t have charges

 

Analysis Data Table –Compiling & Interpreting Results
	Melting Point Order	Solubility	Ionic, Covalent or Polar Covalent?
Substance A	2	Soluble	Polar Covalent
Substance B	3	Soluble	Ionic
Substance C	1	Insoluble	Non-polar covalent

Result

What is the identity of substance A?  What is your evidence and reasoning for this identification?

Substance A has a low melting point which means that it is either a polar or non-polar covalent compound. However this substance is soluble, therefore it is a polar covalent compound. Therefore, substance A is sucrose.

What is the identity of substance B?  What is your evidence and reasoning for this identification?

The identification of substance B be is sodium carbonate. This substance has a high melting point and is quickly dissolved in water, which is two of the identification of an ionic compound.

What is the identity of substance C?  What is your evidence and reasoning for this identification?

Substance C has a low melting point which means that it is either a polar or non-polar covalent compound. However, it is insoluble, which are the identification of a non-polar solvent compound.  Since paraffin wax is the only non-polar covalent compound, substance C is paraffin wax.

One source of error in this experiment could have been the heat intensity of the hot plate, some part of this hot plate might be hotter (the inner part), therefore, the substance that is put in that place might melt faster than the other. This can possibly change the order of which substance starts to melt first.

I would reduce the error and improve the lab by…

I way I would do to reduce this error is to melt the substance one by one, as well as putting that substance on the same location. As well as use timer to record how long it takes to melt each substance.

 

One of the topic that we learned in Chemistry class this term was about Atomic Emission; sets frequencies of the electromagnetic waves that emitted by atoms.

Reason why atoms emit electromagnetic waves:

When atoms receives energy from an external source, the atoms will absorb the energy and become excited, which is when electrons are move to a higher energy orbital. The excited atoms then emit photons of light in order to go back to the ground state, which is.

Introduction to Flame Test Lab: (This introduction was written by our facilitator as the Pre-Lab)

Flame tests provide a way to qualitatively test for the presence of specific elements by seeing colored flames.  The heat of the bunsen burner excites the electrons in the atom, and this energy is released as the electrons “fall back” to their ground states. The color we see is a combination of the visible wavelengths of light emitted by the atoms.  

If you have a spectroscope you can also make quantitative observations. A spectroscope can be used to see a pattern of narrow lights called an emission (bright-line) spectrum.  The actually wavelengths of the spectrum serve as a quantitative test to determine atoms identities.  Each element has a different “pattern” of electrons, so it will show a different combination of colors.  

In this lab you will perform flame tests on seven different elements. You will use your observations to identify an unknown solution.  

Click here to read my lab report.