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Table of Contents
The universe, Earth, and even our body are made up of substances. Not just this, if you go to your kitchen or your bathroom, you will see many examples of pure substances.
See the fact file below for more information on Substances, or you can download our 33-page Substances worksheet pack to utilize within the classroom or home environment.
Key Facts & Information
WHAT ARE SUBSTANCES?
- A substance is a type of matter made up of only one kind of particle or has a fixed structure.
- All samples of a substance must have the same properties. Thus, a substance cannot be divided into simpler or smaller molecules.
- Substances are more commonly known as pure substances or chemical substances. All known pure substances exhibit the following properties:
- Contain only one kind of atom or molecule, making it homogenous in nature;
- Have fixed melting and boiling points; and
- Often take part in chemical reactions to form predictable products.
TYPES OF PURE SUBSTANCES
- A pure substance can either be an element or a compound.
ELEMENTS
- All living and nonliving matter are made up of elements. This type of matter is made up of only one kind of atom. Thus, they cannot be broken down into simpler substances.
- An element is characterized by its number of protons, neutrons, and electrons. There are 90 naturally-occurring elements and 30 additional elements that scientists synthesize.
- The periodic table shows and arranges all known elements according to the number of their protons or the atomic number.
- Elements vary in abundance in the universe, on Earth, and in the human body.
- In the universe, the elements hydrogen and helium are the most abundant. Meanwhile, the Earth’s crust is made up mostly of oxygen and silicon. In the human body, oxygen, carbon, and hydrogen are the most abundant.
COMPOUNDS
- A type of pure substance made up of two or more elements that are chemically combined with one another in a fixed ratio.
- Elements that make up a compound lose some of their individual properties while the compound exhibits new properties.
- There are two types of compounds based on the type of chemical bonds that bind the elements together: salts and molecular compounds.
- Salts are held together by ionic bonds, which is a type of chemical bond formed between a metal and a non-metal.
- Meanwhile, molecular compounds are held together by covalent bonds, which are formed between two non-metal elements.
- Examples of compounds are water (H2O), table salt (NaCl), and carbon dioxide (CO2).
PHASES OF SUBSTANCES
- Matter, such as pure substance, can exist in different phases. There are three principal phases of matter- solid, liquid, and gas.
SOLIDS
- Particles of a solid are compact and closely bound together by molecular forces. There is also little to no space between the particles. Thus, solids have a regular arrangement.
- Due to the arrangement of particles in a solid, they exhibit the following characteristics:
- The particles are vibrating but are generally locked in place;
- Definite mass, volume, and shape;
- Incompressible; and
- Expands when heated.
LIQUIDS
- Particles of a liquid have more space in between than those of solids, but they have no regular arrangement. Due to this arrangement, liquids exhibit the following characteristics:
- The particles are vibrating and can move and slide past one another;
- Definite mass and volume;
- Follow the shape of its container (indefinite);
- Not easily compressed.
GASSES
- Particles of a gas are widely spread out from one another, almost like there are no intermolecular forces binding them together. Just like liquids, gases have no regular arrangement, and particles can move freely and at high speeds. Due to this, gases exhibit the following characteristics:
- Definite mass;
- Indefinite shape and volume- gases can occupy the space and follow the shape of the container;
- Highly compressible.
- A substance can exist in any of the three states of matter through a set of processes called phase change.
- The addition or removal of heat can allow the particles of a substance to change into that of a solid, liquid, or gas.
PURE SUBSTANCES VS MIXTURES
- The term substance can have different meanings depending on the way it is used. However, in chemistry, a substance is a matter with uniform properties. In order to differentiate, we often call substances pure substances.
- On the other hand, mixtures are made up of two or more substances that are not chemically combined.
- Due to the difference in how pure substances and mixtures are formed, they exhibit the following differences:
- Pure substances cannot be broken down into simpler substances or separated into new ones. Meanwhile, mixtures can be broken down or separated using separation methods.
- Pure substances are known to have constant or fixed properties, while mixtures have varying physical and chemical properties.
- Despite the clear difference between pure substances and mixtures, there is still a gray area.
- Mixtures are either homogeneous or heterogeneous. Homogeneous mixtures are often confused with pure substances.
- Homogeneous mixtures have uniform composition throughout the mixture. An example of this is saltwater. The salt is dissolved and evenly distributed throughout the water.
- Due to this similarity, many consider homogeneous mixtures as pure substances, while many don’t.
- To give light to this gray area, let’s take a look at the saltwater. Saltwater is not a pure substance because the concentration of salt may differ from one sample to another. As we know, pure substances have a fixed composition throughout samples.
SOLUTIONS
- A solution is a homogeneous mixture composed of solutes dissolved in a solvent. Solutes and solvents are pure substances.
- Solutes are substances that can either be solid, liquid, or gas. It is the minor component of a solution and is dissolved by a solvent.
- Solvents, on the other hand, are mostly liquids but can also be a solid or gas.
- A solvent dissolves a solute to form a solution.
- A substance can either be a solute or a solvent depending on its proportion. In a solution, the solvent is greater in proportion than solutes.
- Solubility is a property of solutes that allows them to be dissolved in a solvent. There are many factors affecting a solute’s solubility.
- POLARITY: Like dissolves like. This means that solutes can only be dissolved by solvents with the same polarity.
- Polar solutes can be dissolved by polar solvents. An example of this is water dissolving salt, forming saltwater.
- Nonpolar solvents like gasoline cannot dissolve saltwater, but they can dissolve nonpolar solutes such as oil, hydrocarbons, and petrol.
- TEMPERATURE: This is defined as the degree of hotness or coldness of an object. It is also the average kinetic energy.
- Temperature affects the solubility of each state of matter differently. However, the solubility of solids and gases is much more defined than that of liquids.
- For solids, the effect of temperature depends on the type of reaction, whether it is endothermic or exothermic.
- An endothermic reaction is when heat is absorbed, while an exothermic reaction is when heat is released.
- Endothermic reactions increase the solubility of solid solutes, while endothermic reactions decrease the solubility.
- Meanwhile, the opposite is true for gases. Exothermic reactions result in an increase in solubility, while endothermic reactions result in a decrease in solubility.
- PRESSURE: This is defined as the force exerted by a particle per area. This can be measured by determining the collisions made by the particles in the walls of their container.
- The effect of pressure on the solubility of solids and liquids is negligible. However, for gases, pressure and solubility are directly proportional. The increase in pressure results in an increase in solubility.
SATURATED AND UNSATURATED SOLUTIONS
- As mentioned above, there are a lot of factors contributing to the solubility of a solute in a solvent.
- To understand how a solution becomes saturated, it is important that we know what the solution equilibrium, dissolution, and recrystallization are.
- Dissolution is a process wherein a solute dissolves in a solvent. An example of this is when salt dissolves in water.
- Recrystallization is a process wherein the dissolved solute goes back to its solid form. When there is too much salt and the amount of water is not increased, some of the dissolved solutes go back into crystals.
- Meanwhile, solution equilibrium is when the rate of dissolution is equivalent to the rate of recrystallization.
- A solution becomes saturated when the solution equilibrium is reached, and no more solutes are being dissolved.
- A solution that contains the maximum amount of solutes that can be dissolved in a solvent is called a saturated solution.
- Meanwhile, a solution that contains less than the maximum amount of solute that can be dissolved is called an unsaturated solution.
Substances Worksheets
This fantastic bundle includes everything you need to know about Substances across 33 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Substances, which are materials that have a uniform and definite composition.
Complete List of Included Worksheets
Below is a list of all the worksheets included in this document.
- Substances Fact File
- Words Crossing
- Fact Check
- Flask of Facts
- Substances vs. Mixtures
- Which is Which?
- Elements & Compounds
- Faces of Water
- Physical Properties
- How Much Is Too Much?
- What Really Matters
Frequently Asked Questions
What is a substance?
A substance is a material that has a definite chemical composition and physical properties. It can be a pure element such as gold or copper, or a compound made up of multiple elements such as water (H2O) or table salt (NaCl).
What are the types of substances?
There are several types of substances, including:
- Elements: a substance made up of only one type of atom. Examples include gold, copper, and oxygen.
- Compounds: a substance made up of two or more elements chemically combined in a fixed ratio. Examples include water (H2O) and table salt (NaCl).
- Mixtures: a combination of two or more substances that are not chemically combined. Examples include air and seawater.
- Pure Substances: a substance that is composed of only one type of atom or molecule and has a fixed composition.
- Impure Substance: a substance that contains two or more different types of atoms or molecules, and has variable composition.
How are substances classified?
Substances can be classified based on their physical and chemical properties, such as their melting and boiling points, density, solubility, and reactivity. They can also be classified based on their composition, such as whether they are an element, compound or mixture.
What are the properties of substances?
The properties of a substance include its chemical and physical characteristics. Chemical properties include reactivity, flammability, and toxicity. Physical properties include density, melting and boiling point, color, and texture.
How do substances change?
Substances can change in many ways, including through chemical reactions, physical changes, and phase transitions. Chemical reactions involve the formation of new substances through the combination or breakdown of existing ones. Physical changes include changes in the substance’s state, such as melting or boiling. Phase transitions involve changes between solid, liquid, and gaseous states.
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Link will appear as Substances Facts & Worksheets: https://kidskonnect.com - KidsKonnect, January 23, 2023
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