Substance - Properties and Changes

IBYXO - Something that occupies space and has mass is a substance, the objects around us are never separated from the name of the substance. 

These objects can change from one form to another. For example, heated water will change its form from liquid to water vapor. Surely many are wondering about that, here's an explanation of substance changes.

A. Properties of Substances

1. Physical Properties

Substances have their own characteristics. You can bend a copper wire easily, while an iron bar is difficult to bend. The characteristics of a substance that can be observed without changing the substances that make up the material are called physical properties. The physical properties of an object include:

a. Form of Substance 

Three kinds of forms of substances that we know are: solid, liquid and gas. The substance can change from one form to another. Some of the changes we are familiar with are: evaporating, condensing, melting, freezing, sublimating, and crystallizing. Substances have different boiling points and melting points for each type of substance. The boiling point of water at normal air pressure (76 cmHg) is 100°C, while gasoline is approximately 80°C.

b. Color 

Every object has a different color. Color is a physical property that you can observe directly. The color of an object is a distinctive feature that distinguishes one substance from another. For example, milk is white, carbon is black, nails are gray and others.

c. Solubility 

Water is a solvent for solutes. Not all substances can dissolve in solvents. For example, salt can dissolve in water, but coffee cannot dissolve in water. The solubility of a substance in a particular solvent is a physical property.

d. Electrical conductivity 

Metal objects can generally conduct electricity. Objects that can conduct electricity well are called conductors, while objects that cannot conduct electricity are called insulators. Electrical conductivity in a substance can be observed from the symptoms it causes. For example, copper is connected to a voltage source and a lamp. The result that you can observe is that the lamp can light up. Electrical conductivity is a physical property. 

e. Magnetism 

Based on the nature of magnetism, objects are classified into two, namely magnetic objects and non-magnetic objects. Magnetic objects are objects that can be pulled strongly by a magnet, while non-magnetic objects are objects that can not be pulled by a magnet. For example, there is a mixture of iron powder and sand. Separation of this mixture cannot be done by sifting or sieving. An easier way is to bring a magnet closer to the mixture. Iron powder is magnetic, so it will be attracted to the magnet. Physical differences such as the attraction of an object to a magnet can be used to separate substances in a mixture. Try to gather some other information about the physical properties of objects!

2. Chemical Properties

Chemical properties are characteristics of a substance that relate to the formation of new types of substances. Look at the metals around you, can they all react with oxygen? Iron is a substance that reacts easily with oxygen, so it can cause iron to rust. Here are some examples of chemical properties possessed by an object, namely:

a. Flammability 

Have you ever noticed why there is a "No Cell Phones" ban at fuel stations? This warning aims to remind consumers that gasoline is a flammable substance. By knowing the nature of flammable materials, we will be able to use them safely. 

b. Foul and sour 

As a result of a chemical reaction in a food or drink, it can cause the food and drink to rot and turn sour. For example, rice that is left for days reacts with air to become stale, milk that changes its taste to sour. 

c. Rusting 

The reaction between metal and oxygen can cause the object to rust. Metals, such as: iron and zinc have the property of rusting easily. There are objects that cannot rust, such as: plastic and glass. Rusting is a chemical property, because there is a reaction that produces a new type of substance.

d. Explosive 

The interaction of substances with oxygen in nature has explosive properties, such as: magnesium, uranium and sodium. 

e. Poison 

There are several substances that have toxic chemical properties, including: insecticides, pesticides, fungicides, herbicides and rodenticides. These toxic substances are used by humans to get rid of pests, both insects and rats.

B. Physical Changes

Physical changes are changes in substances that do not produce new types of substances. For example, rice is ground into flour. Rice that is ground into flour, only shows a change in shape and size, but the molecular properties of substances in rice and flour remain the same. Events that change the form of substances, including: evaporating, condensing, melting, freezing, sublimating, crystallizing are physical changes. There are several characteristics of physical changes, namely: no new type of substance is formed, the changed substance can return to its original form, followed only by changes in physical properties. Changes in physical properties that appear are shape, size, and color changes.

C. Chemical Change

Chemical changes are changes in substances that produce new types of substances. Have you ever burned paper? What can you see after the paper has burned? There is ash obtained as a result of the combustion process. The paper before burning has different properties from the paper after burning. Examples of chemical changes include: rotting rice, spoiled milk, spoiled vegetables, rotting eggs, salted eggs, rusty iron, and others.

There are several characteristics of chemical changes in a substance, namely: a new type of substance is formed, the changed substance cannot return to its original form, followed by changes in chemical properties through chemical reactions. During chemical changes, the mass of the substance before the reaction is the same as the mass of the substance after the reaction.

D. Changes in Mixtures

Every substance is composed of very small particles. The existence of particles can be proven, for example, a spoon of table salt is dissolved in a glass of water. What can you feel when the solution is tasted? Doesn't it taste salty? How can we get salt that has been dissolved in water? Try to heat the salt solution until it boils, so that all the water evaporates. You will get the salt back. 

This shows that the separation of mixtures can be done based on the difference in boiling points between the constituent particles. Separation of mixtures can be done in various ways, including:

1. Filtration

Separation of sand with gravel and separation of water with grated coconut aims to separate the substances mixed in the mixture. Particles that have a smaller size will escape from the sieve while those with a large size will be retained on the sieve.

Water seeps into the soil through small cracks, and is filtered by the soil layer, resulting in a clear water source. In laboratory activities, mixture separation can be done using filter paper. The choice of filter size is adjusted to the size of the substance to be separated. Separation of mixtures with respect to differences in solubility can also be done by filtration. For example, we want to separate a mixture of salt and sand. The step we take is to give water to the mixture. Water is a solvent for substances that have dissolved properties. In this case, salt can be dissolved by water, while sand cannot. Through the filtering process the sand will be left behind, while the salt water escapes from the filter. Substances that are retained and left on filter paper are called residues. The liquid that can escape from the filter paper is called filtrate.

2. Distillation (distillation) 

Distillation or distillation is the process of separating a mixture of liquid substances based on the difference in boiling points of substances. The process of separating the mixture by distillation is done by two processes, namely evaporation and condensation.

3. Crystallization 

Solids cannot be separated from the solution by filtering. Solids, such as sugar and salt dissolved in water can be separated from the solution by evaporation and crystallization occurs. Salt farmers get salt by evaporating seawater. How do salt farmers get salt from seawater? Seawater is channeled to the ponds that are made on the beach. This flow of seawater can occur due to one of the natural events, namely tides that are influenced by the gravity of the moon. After the seawater is trapped in the ponds, then the evaporation process occurs with the help of sunlight. The water contained in seawater will evaporate, resulting in the formation of salt crystals.

4. Sublimation 

Separation of mixtures with sublimation is done on substances that can sublimate. Sublimation is the change of substance from solid to gas or vice versa. Substances that can sublimate, among others: camphor, iodine, caffeine and others.

5. Chromatography 

The process of separating a mixture based on the difference in speed of propagation between particles of substances mixed in a medium is called chromatography. An activity that you can do, for example, how to separate a black mixture? Black ink is a mixture of several colors. The separation of black into its constituent colors can be done by chromatography.

Some of the information above is only a partial explanation of substance changes, hopefully it can be a reference for all of you.