Using English to Give Evidance (resume 4)

Signs and Evidence Of Chemical Reaction

There are a variety of signs that may provide clues that a chemical change has entered the building. Let's look at the following five signs:

1. Odor
2. Gas bubbles
3. Precipitate formation
4. Color change 
5. Temperature change
6. Lighting
7. Volume Changes occur
8. Conductivity change
9. Pain Changes
10. There is a change of Boiling Point and Freezing Point

Odor

Have you ever witnessed the awful sight and smell of spoiled food? Some chemical compounds (such as ammonia) have a strong odor. Then the formation of ammonia or other odorous compounds will cause odor changes in the system. Before going bad, a chemical change must take place. The evidence of the chemical change in our food is the offensive smell. Not all the smells are bad however; the delicious smell of baking bread is due to chemical change as well.

You must have been drinking soft drinks, have not you?
The presence of foam is proof that in the soft drinks gas results from chemical reactions in it. In life, many chemical reactions produce gas. This gas can be produced from the reaction of two kinds of substances that are not gas. Zinc that reacts with sulfuric acid (H2SO4) produces hydrogen gas (H2) by the following reaction. 

Zn + H2SO4 → ZnSO4 + H2 (gas) 

Thus, one characteristic of a chemical reaction is the formation of a gas as a reaction.

To distinguish the types of gases that occur in chemical reactions can be seen from the properties of these gases. For example:

1. Hydrogen gas (H 2) will produce small eruptions when the gas is applied to the embers; 
2. Oxygen gas (O2) will cause a blazing fire, 
3. Carbon dioxide (CO2) gas will kill the embers; 
4. Ammonia gas (NH3) emits a pungent odor; 
5. Sulfur oxide gas (SO2) and hydrogen sulfide gas produce a foul odor.

Gas Bubbles

When a chemical reaction produces a gaseous product, this is an indication that a chemical change is occurring. Visually, this gaseous product is simply the presence of bubbles. This reaction can occur between two liquid solutions or even a solid added to a liquid solution. A great example can be the mixture of baking soda, a solid, with vinegar, a liquid. When you mix the two substances together, a chemical change occurs, and you can tell based on the appearance of less and lots of bubbles. Bubbles can arise from warming up a liquid or forming a gas in a liquid. Both of these are common chemical reactions.

Formation of a Precipitate

A precipitate is a fancy term for a solid substance. If you ever mix two solutions together and see a solid substance form in the container, that is a precipitate. This gives you evidence that a chemical change is taking place. When you mix potassium iodide with lead (II) nitrate you produce a beautiful yellow precipitate called lead (II) iodide. When mixing two substances soluble in the solvent, then forming a solid at the bottom of the solution, this indicates the occurrence of chemical reactions in the solution. The formation of this precipitate is sometimes a very small particle (micro) that hovers in solution so that it is invisible. To be sure you can light the light on the solution. This phenomenon is known by the name of Brown Effect (Brown Effect)

Around us there are many chemical reactions that can produce sediment. Try to observe the bottom of the pot used to boil water, is there any substance that sticks to the bottom of the pan? It is a carbonate compound formed when water containing lime is heated.Activity Lab. The reaction between lime water and CO2 gas

1. Take half a glass of lime water
2. With the help of the hose, blow the lime water in the glass until color changes occur
3. Let stand for a moment and observe the changes that occur.

Analysis 

1. What evidence has there been a reaction between lime water and carbon dioxide gas? 
2. What is the reaction between lime and carbon dioxide gas?
3. Mention the reactants and the reaction product.

In the above lab activities, when lime water is blown, there will be a reaction between lime water and carbon dioxide from the breath. The occurrence of the reaction can be observed the formation of white calcium carbonate (CaCO3) that settles on the bottom of the glass if left for a while. The reaction is one example of a chemical reaction that produces precipitate.Precipitation by chemical reactions has long been used for water purification processes. The muddy well water mixed with mud can be clarified with the addition of alum. Tawas will bind the particles of mud so that clot and eventually settles.

Color Change

Have you noticed the changes that occur when the apple is cut and left for a while? Fresh apple fruit will gradually turn into brown. This color change indicates that the chemicals in apples have reacted with oxygen in the air.The reaction between the starch starch solution with iodine tintur can be known from the color change that occurs. Color clear starch solution, brown iodine. If both are mixed will form a blue color. If added vitamin C then iodine will react with vitamin C to form other chemicals that are colorless. So the occurrence of chemical reactions can be known from the color changes that occur.Note the household appliances made of metal, the objects will gradually change color. The tool of iron will rust so that it becomes black, copper tools will change color to greenish, the tool from silver will change color to black. The color change indicates that there has been a chemical reaction to the alatalate. The color of the clothes we wear will fade as it reacts with the chemicals contained in the detergent.

Some chemical compounds have a tendency to absorb and radiate color. The ability to absorb and transmit color is very specific for some substances. So when there is a change (conversion) of the substance of the reactant into a product (new compound) then there will be a change of color. It could be that from two colorless reactants will produce a product of colored compounds, or from colored reactants to form colorless products. This incident indicates a chemical change (Chemical Reaction).

Temperature Change

Did you know that chemical changes can cause temperature changes in reacting substances? However, can temperature change affect the rate of chemical reactions? Does the particle size of the reacting agent affect a chemical reaction? The particle size of the reacting agent affects the speed of the chemical reaction process. The smaller the particle size of the reacting agent, the faster the reaction process. Heating or temperature administration of a chemical reaction affects the rate of reaction. Some are accelerating, but others slow down the reaction process. In exothermic chemical reactions, heating will slow down the process of reaction, whereas in endothermic chemical reactions, heating will speed up the process of chemical reactions.

Each chemical compound has an inner energy. This inner energy is a chemical bond energy in a compound. Breaking bonds requires energy, while the formation of chemical bonds releases energy. When the chemical reaction that occurs causes more formation of chemical bonds than the breaking of chemical bonds, the energy will be excess and released as heat and temperature rise. But if a chemical reaction involves more bond breaks than bond formation, then the energy will be less and absorbed from the environment causing cold and decreasing temperature. 

Remember that chemical changes tell you a chemical reaction is taking place. During chemical reactions, bonds that hold atoms together are constantly broken and formed, requiring or releasing energy. This energy directly affects temperature. For example, if we grab our flask and conduct a reaction where bonds are broken, we will see that a lot of energy is needed to break those bonds. By absorbing energy, don't be alarmed if the flask feels cold during the reaction.

In physics changes there are many changes that result in temperature changes. For example, it freezes, the physics changes that release energy.
Melting is a physics change that absorbs heat energy. One of the energies that follow a chemical change is heat energy. Chemical reactions that release energy are called exothermic reactions, while chemical reactions that absorb energy are called endothermic reactions. It can be concluded that the temperature change in one reaction is one of the characteristics of the occurrence of chemical reactions.

Lighting

When energy is released, it can sometimes be in the form of light, like in the glow emitted after you break a glow stick. When you're bending it, you're breaking a little tube inside that releases a liquid into the outer tube. The mix of chemicals together causes a chemical reaction that releases light as a byproduct. 
Chemical reactions sometimes release energy in the form of light. An example of this chemical reaction is in fireflies that emit light during the night. 
Volume Changes occur 

When a new compound (product) is formed, the reactant compound will decrease drastically. The formation of new compounds and the reduction of these reactants can lead to drastic density changes so that the volume changes.

Conductivity change

Some chemical reactions can produce or convert ions into other compounds. This will affect the changes in the conductivity of a system.
 
Pain Changes

Chemical compounds that have a certain taste will cause a sense change when reacting. This can be easily observed when we boil yam, at first the taste of sweet potato is not too sweet, then after boiled will form glucose that has a sweet taste. 

There is a change of Boiling Point and Freezing Point

Generally this happens to the crystal. To know a crystal has reacted or not, it can use its boiling point and freezing point. 

CHEMICALS IN DAILY LIFE

The development of science and technology has produced industrial products that can meet the needs of everyday people. Chemicals that have been known for their benefits are developed by making products useful for the benefit of humans and their environment. Therefore, we need to know the types, traits, uses, and side effects of every product we use or see everyday.
Many kinds of chemicals that exist in everyday life. Some groups of chemicals in question, among them are: 
1. Cleaners
In everyday life, we are familiar with various cleaning chemicals, including soaps and detergents.The types of chemicals that can be used as a cleanser include:- Body cleanser- hair cleanser- motor and car cleaners- plate cleaners- cleaning clothes- floor cleanerWe need to be careful in choosing cleaning materials, the material should not cause a bad influence on the environment. Some types of detergents are difficult to decipher by decomposers. If the detergent is mixed with groundwater that is used as a source of drinking water for humans or livestock then the ground water will endanger health. Therefore, it is better to choose detergents whose waste can be decomposed by microorganisms (biodegradable).
Adverse effects that can be caused by the use of detergents that are not selective or not careful are:- Increase household waste in the form of foam.- The soap-generated foam can be broken down by microorganisms present in the soil, whereas the foam 
   produced from the detergent is difficult to decompose by microorganisms in the soil 
PreventionPrevention that can be done, among others, as follows.- Use detergents with dilute concentrations and low levels of ABS.- Use a biodegradable detergent, such as sodium dodecyl sulphate (SDS).- Keeps the soap in the right place so it is out of reach of the child.
2. Bleach
Bleach is usually sold in the form of a solution and is used to remove impurities or colored stains that are difficult to remove by using only soap or detergent. Bleach solutions sold on the market usually contain sodium active ingredientsHypochlorite (NaOCl) about 5%. Besides being used as bleach and cleaning stains, it is also used for disinfecting (disinfecting germs). In general, whitening agents sold on the market are safe to use during use in accordance with the instructions. In addition to the stain, this substance can also react with the dye clothes so that it can fade the color of clothing. Therefore, the use of this bleach should be as directed.- How bleach can remove stubborn stains on white clothing?- In bleach ingredients contain Ca (ClO2) hypochlorite usually known as chlorine, and bleach solution 
  containing sodium hypochlorite (NaClO). The bleach will oxidize the impurities so that the impurities will 
  dissolve in water
Side Effects of Bleach Usage- Clothing bleach materials generally contain chlorine compounds that can damage fabric fibers and clothing 
   colors.- Chlorine compounds can also cause skin irritation.- Skin whitening ingredients that contain mercury or excessive mercury can damage the nervous system
PreventionPrevention that can be done for the use of bleach, among others:- Avoid using bleach types containing mercury.- Only use bleach products if dirt or stains are difficult to remove by soap or detergent.
3. Fragrance
Fragrance is another chemical that is closely related to our daily life. We can obtain deodorant from both natural and synthetic materials. In addition to substances that give rise to fragrance, fragrances sold on the market usually contain other substances, such as alcohol for liquid perfumes and alum for fragrance-shaped solids.In addition to alcohol, there are still a variety of other additives that are deliberately added to the perfume so that the perfume is easily sprayed (the substance serves as propellant). Among the additives that can serve as propellants there are those that can pollute the environment. Certain propellants if released into the air and then into the upper atmosphere will damage the ozone layer. It also affects human health such as irritating the eyes, nose, throat, skin, resulting in nausea, dizziness, bleeding, loss of memory, cancer, and tumors, liver damage, causing mild to moderate irritation of the lungs, including symptoms such as asthma 

4. Pesticides
Pesticide-type chemicals are closely related to the lives of farmers. Pesticides are used to eradicate plant pests so as not to disrupt agricultural production. Pesticides commonly used by farmers can be classified according to function and targetIts use, namely: 

1. Insecticides, ie pesticides used to eradicate insects, such as grasshoppers, ladybirds, aphis, and caterpillars.
2. Fungicide, a pesticide used to eradicate and prevent the growth of mold or fungus.
3. Bactericide, ie pesticides to eradicate bacteria or viruses.
4. Rodenticide, a pesticide used to eradicate plant pests in the form of rodents, such as rodents.
5. Herbicides, ie pesticides used to eradicate weeds (weeds), such as reeds, grasses, and water hyacinths.

Side Effects of Insect Repellent Products

1. Anaerosol insecticide products can cause depletion of the stratospheric ozone layer. 
2. Ozone depletion will increase the number of skin cancer patients significantly, including malignant melanoma, and people with cataracts. 
3. Can damage agricultural products. Anti-mosquitoes belong to the pesticide group (pest eradication), so the antinyamuk drug also contains toxins.

Alternative1. Not using pesticides containing chemicals such as carbamate, phosphate, and chlorine compounds.2. Use of organic pesticides and biopesticides (natural enemies).3. Latest technology usage.