The role of chemists
Open-Book Paper It was Lavoisier who divided the few elements known in the 1700's into four classes, and then John Dalton made atoms even more convincing, suggesting that the mass of an atom was it's most important property. In the nineteenth century Johann Döbereiner was the first to attempt to classify elements using their relative atomic mass. He also identified a number of 'triads' in the list of elements then known. Each triad was a set of 3 elements that have similar properties (e.g. Cl, Br and I; Ca Sr and Ba). In 1863, John Newlands noted that when the known elements were written in order of increasing relative atomic mass, every eighth element has similar properties. He called this the Law of Octaves. (There were only seven elements in each period at this time because the noble gases had not been discovered yet). After 20 elements his table did not make any sense, he had 2 elements in one space because the relative atomic mass values that had been used were incorrect. He was quite close to the right answer. Six years later in 1869 professor Dimitri Mendeleev came up with a periodic table that ours is based on today. A whole new group was added as the noble gasses were found; all the gaps have been filled. Elements are arranged in order of increasing atomic number, rather than relative atomic mass. He amended some relative atomic masses and he also left gaps for
Sludge Test Lab Report.
Sludge Test Lab Report Eric Walk Michael Cruz Science 8 Mr. C. Johnson We hope to accurately separate a test tube of "sludge", by firstly, separating the different substances and by secondly, testing the individual substances for their characteristic properties. We used the following apparatuses to fulfill our above hypothesis: Micro-Burner, Ring Stand, Spoonula, Forceps, Chemical Spoon, Tongs, Sparky, Burette Clamp, Test Tube Holder, Screen W/Ceramic Circle, Evaporating Dish, 600mL Beaker, Lg. Test Tube, Sm. Test Tube, Lg. Stopper, Sm. Stopper, Lg. Stopper W/Hole(s), Sm. Stopper W/Hole(s), Tape, Filter Paper, Funnel, Paper Towel, Condensation Apparatus, Distillation Apparatus, Pen, Sieve, Triple Beam Balance, Internet, Calculator. Examine sludge in its original container. Draw detailed illustration of the shape, size and color of the layers. Mass a single piece of filter paper. Set up filtration apparatus. Separate solids from liquids in the sludge by means of filtration. It is important to cover the top of the funnel when filtering to avoid the liquid evaporating. Record all observations. Wrap filter paper in paper towel and let dry over night. Mass the dried filter paper and subtract the mass of the filter paper. Mass the boiling chips put the chips into the test tube with the liquid. Set up distillation apparatus and distill the liquid. Record all observations. Mass
Covalent Bonds
Covalent Bonds Covalent bonds are formed when atoms share electrons, one from each atom in a single bond, to form electron pairs, usually making their outermost shells up to eight electrons by this means. This would make them more stable, less reactive and an electronic structure like a noble gas. They are most frequently formed between pairs of non-metallic elements. Non-metallic elements usually have from four to eight electrons in their outermost shells, the so-called valency electrons, which are used for chemical bonding. In any given "full" shell of eight electrons, the electrons occur in four pairs, but in incomplete shells, the electrons exist singly where possible. Sometimes, atoms of elements form covalent bonds with other atoms of the same element. Thus two chlorine atoms form the chlorine molecule, Cl2, by sharing their unpaired electrons. In the case of oxygen (O2), there are two unpaired valency electrons in each atom, so that two electron-pair bonds are formed between the two atoms to complete their octet of electrons, a double bond. Covalent bonds can also be formed in such a way as to form a giant molecule, such as happens in diamond. Here, each of the four valency electrons of a carbon atom is shared with one of the valency electrons of another carbon atom, so that every carbon atom in the structure has four different carbon atoms bonded to it. In
The Sub-atomic particles
Foundation Chemistry The Sub-atomic particles Atoms are made of three main particles: protons, neutrons and electrons. > The protons and neutrons form the nucleus, in the centre of the atom > Protons and neutrons are sometimes called nucleons, because they are found in the nucleus. > The electrons surround the nucleus Properties of the sub-atomic particles PROPERTY PROTON NEUTRON ELECTRON Mass/kg .673 x 10 -27 .675 x 10-27 0.911x 10-30 (very nearly 0) Charge/C (Coulombs) +1.602x10-19 0 -1.602 x10-19 Position In the nucleus In the nucleus Around the nucleus These numbers are extremely small. In practice we use relative masses and charges. Relative atomic mass, Ar The relative atomic mass of an element is the average mass of the naturally occurring isotopes of the element relative to the mass of an atom of 12C (one atom of carbon 12 is given a relative atomic mass of exactly 12) ATOMIC NUMBER, Z=NUMBER OF PROTONS=NUMBER OF ELECTRONS Relative Isotopic mass The relative isotopic mass is the mass of an isotope of an element relative to the mass of an atom of carbon 12 (one atom of carbon 12 is given a relative atomic mass of exactly 12) Relative Molecular Mass, Mr The relative molecular mass of a compound is the mass of a molecule of the compound relative to the mass of an atom of carbon 12 (one atom of carbon 12 is given a relative atomic mass of
Dalton's Atomic Theory
Dalton's Atomic Theory It was in the early 1800s that John Dalton, an observer of weather and discoverer of color blindness among other things, came up with his atomic theory. Let's set the stage for Dalton's work. Less than twenty years earlier, in the 1780's, Lavoisier ushered in a new chemical era by making careful quantitative measurements which allowed the compositions of compounds to be determined with accuracy. By 1799 enough data had been accumulated for Proust to establish the Law of Constant Composition ( also called the Law of Definite Proportions). In 1803 Dalton noted that oxygen and carbon combined to make two compounds. Of course, each had its own particular weight ratio of oxygen to carbon (1.33:1 and 2.66:1), but also, for the same amount of carbon, one had exactly twice as much oxygen as the other. This led him to propose the Law of Simple Multiple Proportions, which was later verified by the Swedish chemist Berzelius. In an attempt to explain how and why elements would combine with one another in fixed ratios and sometimes also in multiples of those ratios, Dalton formulated his atomic theory. The idea of atoms had been proposed much earlier. The ancient Greek philosophers had talked about atoms, but Dalton's theory was different in that it had the weight of careful chemical measurements behind it. It wasn't just a philosophical statement that there are
To compare the mass of ammonium chloride to its temperature change when water is added to it.
To compare the mass of ammonium chloride to its temperature change when water is added to it. Aim: To see the temperature change when different amounts of ammonium chloride are added to water. Resources: Before doing the experiment I looked at the book "The Material world" and "GCSE revision guide" and have found information on endothermic reactions. I have highlighted the relevant information in my scientific knowledge. This information will help me make a prediction. Scientific Knowledge: There are two types of reactions, exothermic and endothermic reactions. I will be concentrating on endothermic reactions as the reaction I am to plan is going to be endothermic. An endothermic reaction is when energy is gained, and therefore the temperature of the reaction decreases when the two substances are mixed. So when a solid dissolves, energy is used to break up the giant lattice. The energy used is greater than the energy released by the water molecules that surround the dissolved ions, therefore temperature falls. When mass is added to an endothermic reaction the temperature falls at a proportional rate to when mass is added. Prediction: I predict that when the amount of ammonium chloride is increased, the temperature will decrease at a proportional rate to when mass is added which will produce a graph like this, This shows that mass and temperature in an endothermic
Data Analysis: Materials
Aim of the Investigation The aim of the investigation was to investigate the tensile strength of different materials. I chose to use tights which had a different denier. Planning the investigation I will be using three different types of tights (10 denier, 15 denier, and 40 denier) and I will be measuring the tensile strength of each of them. To measure the strength of each sample of material, I will use weights to see how far the different samples will stretch, and then I will use a ruler to measure how long the material has become. To make this a fair test, and to make fair comparisons between different material samples, I will need to keep some things the same. These are: * The length used of tights * The starting weight * The total weight added * Use the same apparatus * Use the same colour, brand and size (e.g. Small, medium, large) of tights The one factor I will be changing in my test is the denier of tights. To make sure my results are dependable, I will repeat the experiment three times for each different type of tights and then work out the average. The apparatus I will need to use to carry out this test are: * Clamp and stand * Newton weights * A weight holder * Ruler * Bulldog clips * Samples of 15 and 40 denier tights Below is a diagram of the apparatus I would use and how I would set up the experiment: It is important that I make sure my
Investigation to find out the empirical formula of magnesium oxide.
Investigation to find out the empirical formula of magnesium oxide. ` Aim. To find out the empirical formulae for magnesium-oxide Introduction. The empirical formula of a compound tells us the types of atoms present in a compound as well as the simplest whole-number ratio of the different types of atoms. The empirical formula does not tell us the actual number of atoms in the molecule. The mass of Mg + the mass of O2=mass of MgxOx. Knowing the mass of magnesium used and the mass of magnesium oxide produced you can determine the mass of oxygen used. The ratio between number of moles of magnesium used and number of moles of oxygen used can be calculated and the empirical formula can be written on the basis of this ratio. Prediction. I predict that magnesium can and will join with oxygen to become magnesium oxide (MgO) because magnesium is in group 2 and can has -2 bands. Both magnesium and oxygen need to join each other to lose or gain electrons. Magnesium: Oxygen: Mg²+O²¯=MgO When magnesium and oxygen coincide they cancel each other out and therefore are completely compatible. Apparatus. . Bunsen burner 2. Tripod 3. Gauze 4. Crucible and Lid 5. Tongs 6. Heatproof mat 7. Safety glasses 8. Magnesium Diagram. Method. . Place a clean, dry crucible (check for any cracks) with its cover on a clay triangle supported by a tripod. Adjust the flame of a Bunsen
Affect of concentration on reaction
In this investigation I am planning to look at the effect of concentration on rate of reaction. The reaction I am going to use is calcium carbonate (chalk or marble chips) reacting with different concentration of hydrochloric acid. The following are the equations for the reaction: Calcium Carbonate + Hydrochloric Acid Calcium Chloride + Water + Carbon Dioxide CaCO3 (s) + 2HCl (aq) CaCl2 (aq) + H2O (l) + CO2 (g) As I am only looking at the effect of concentration has on the rate of reaction, other factors (i.e. temperature and surface area) which will affect the rate of reaction must not vary for it to be a fair test. The rate of reaction is calculated by measuring the mass loss due to carbon dioxide given off during the reaction. I choose to use calcium carbonate because it is not a very reactive compound so the rate of carbon dioxide produced will not be too fast to be recorded inaccurately. I choose not to monitor the gas produced using a gas syringe because it can easily be stuck and it is hard to read while moving therefore I choose to use an electronic scales to measure mass loss. I am aiming to obtain two sets of results with five different concentrations each. The repeated results should be approximately the same with the first set (if not I would carry out the experiment again and obtain another set of results, until two sets are roughly
The disposal of chemicals
M1 unit 2:- The Disposal of Chemicals. How is Mercury disposed of: - Handle the mercury carefully. Wear rubber gloves and scoop it onto a sheet of paper or suck it up with an eyedropper. Place the mercury in a medicine vial or similar airtight container. The scoop, paper or eyedropper should also be bagged and disposed properly according to guidance provided by environmental officials or your local health department. Why dispose of mercury, and what would happen if we didn't: - Otherwise it would contaminate the water, and from then onward goes down a very long chain of reactions and how it would be passed on, the fish in the sea would pick up the mercury in the water and most probably would poison the fish, and from there us human catch the fish to eat and if someone caught an infected fish and were to eat it they would become very ill and most probably die, especially if a pregnant woman ate an infected fish because usually the baby would come out deformed. Elemental mercury exists as a silvery liquid and an odourless vapour at room temperature. It is eliminated in urine, faeces, saliva, and sweat and by exhalation when it is taken in by the body. How is Hydrochloric acid disposed of: - Small amounts of dilute hydrochloric acid can be flushed down a sink with a large quantity of water, unless local rules prohibit this. Larger amounts should be neutralised
