The Law of matter conservation states that matter cannot be created or destroyed, only changes its form. It can go through either a physical or chemical change. In this article, we'll learn what these changes look like, how they help us identify substances, and the key differences between physical and chemical changes.

Physical and chemical properties are characteristics that help us identify substances. Physical properties are traits that can be seen and/or measured without changing the identity of the substance, such as color, density, and mass. Intensive physical properties do not depend on the amount of material, such as boiling point, density, or temperature, while extensive physical properties do depend on the amount, such as mass, length, and shape. Other examples of physical properties are malleability, hardness, solubility, and electrical conductivity.

Chemical properties are the ability of a substance to undergo a specific chemical change. To identify a chemical property, we look for a chemical change. Examples of chemical properties include flammability, reactivity, and toxicity. Physical changes are changes that alter the form of a substance without changing its chemical composition. Examples of physical changes include melting, freezing, boiling, condensation, and sublimation. Chemical changes, on the other hand, involve a chemical reaction that changes the composition of a substance. Examples of chemical changes include burning, fermentation, rusting, and cooking. The key difference between physical and chemical changes is that physical changes do not alter the chemical composition of a substance, while chemical changes do.

Based on our chart, we can determine that Ball 1 is aluminum, Ball 2 is iron, and Ball 3 is silver. This is due to the fact that each metal has a unique density. Density is a physical property, which is a characteristic of matter that is not associated with a change in its chemical composition. Physical properties include density, color, hardness, melting and boiling points, and electrical conductivity.

To calculate the density of each ball, we would first weigh the balls using a scale to determine mass. Then, we would determine volume using a method called water displacement. This involves filling a beaker with a known amount of water (let's say 50 mL), then dropping the ball inside this beaker. We would then measure the new volume of the water and subtract that from the initial to get the volume of the ball.

Chemical properties, on the other hand, describe the ability of a substance to undergo a specific chemical change. For example, flammability determines how likely something will catch fire. A key difference between a chemical and physical property is that a physical property describes what a substance currently is while a chemical property describes what a substance can do.

Chemical properties can help us distinguish substances. For example, the ability of iron to rust is a chemical property. To identify substances using chemical properties, we can perform chemical reactions and observe how the substances behave. For instance, if we are given two silvery lumps of metal and challenged to determine what they are based only on chemical properties, we can take a small piece of each of our metals and place them in water. If one reacts violently due to the creation of hydrogen gas, it is potassium. If the other doesn't react with water under normal conditions, it is tin^[1].

Physical changes are changes that do not change the identity of the substance. Examples of physical changes include changes in the state of matter, cutting/bending/breaking, separation of a mixture, and creation of a mixture. When we melt ice, it becomes water, but the atomic structure remains the same. Mixtures are substances made up of two or more compounds or elements that are uniform. They can be homogeneous or heterogeneous. Homogeneous mixtures are uniform throughout, while heterogeneous mixtures are not. A mixture is reversible using only physical changes such as boiling, sifting, or separating by density.

Chemical changes, on the other hand, change the identity of the substance. Examples of chemical changes include burning, fermentation, rusting, and cooking. Chemical changes are usually irreversible and require another chemical change to be reversed.

To summarize, the key component of a chemical change is that the identity of the reactant(s) is changing, while physical changes do not change the identity of the substance. Physical properties are traits that can be seen and/or measured without changing the identity of the substance, while chemical properties describe a substance's potential to undergo a chemical change. Examples of physical changes include changes in state, cutting/bending/breaking, and separation of a mixture, while examples of chemical changes include burning, fermentation, rusting, and cooking. Chemical changes are usually irreversible and require another chemical change to be reversed, while physical changes are reversible using only physical methods such as boiling, sifting, or separating by density.

Physical and Chemical Changes

What is the difference between a physical and chemical change?

A physical change doesn't alter the identity of the substance, while a chemical change does. 

What are physical and chemical changes?

A physical change is any change that doesn't alter the identity of a substance. It can be reversed by another physical change. A chemical change is any change that does alter the identity of a substance. It may be reversed by another chemical change, but not always. 

How is energy involved in physical and chemical changes?

Energy can be released or required for both physical and chemical changes. 

What properties stay the same during physical and chemical changes?

It is dependent on the type of change. For physical changes, the intensive properties stay the same (those not dependent on mass), as well as the chemical properties. For chemical changes, since the identity of the substance is changing, the physical and chemical properties will change. 

Which processes are an example of a physical and chemical change?

An example of a physical change/process is ice melting. For a chemical change/process, an example would be a log burning.

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