Question

During a 1 h period, make a list of all the changes that you see around you and that involve matter. Note whether each change seems to be a physical change or a chemical change. Give reasons for your answers.

Short answer

Observe changes in matter, categorize them as physical or chemical changes, and provide reasons for each categorization.

Step-by-step solution

- Identify Observations Involving Matter

Observe your surroundings for one hour and make a list of all changes involving matter. These can include things like melting ice, burning candles, rusting metal, boiling water, or mixing substances.

- Categorize Each Change

For each change observed, categorize it as either a physical change or a chemical change. Use the definitions: Physical changes do not change the composition of the substance, while chemical changes result in the formation of one or more new substances.

- Provide Reasons for Each Categorization

For each change, explain why it is a physical or chemical change. For example, melting ice is a physical change because it changes from solid to liquid without changing its composition. Burning a candle is a chemical change because it produces new substances like carbon dioxide and water vapor.

- Compile Your Findings

Create a final list that includes each observation, its categorization, and the reason for the categorization.

Key concepts

Matter

Matter is everything around us. It is anything that occupies space and has mass. Examples include water, air, rocks, and even living things like plants and animals.
Matter can exist in different states: solid, liquid, and gas. For instance, water can be ice (solid), liquid water, or steam (gas).
Understanding the properties and changes of matter is essential in science because it helps us to identify and categorize what we observe.

Physical Change

A physical change affects the form of a substance but not its chemical composition. It means that no new substances are formed during a physical change.
Common examples include melting ice, tearing paper, and boiling water. In each case, the substance itself doesn't change what it is, only how it appears or behaves. For example, melted ice becomes water, but it's still H2O.
Physical changes are often reversible. For instance, you can freeze melted ice again to return it to its solid state.

Chemical Change

A chemical change results in the formation of one or more new substances. These changes often involve a chemical reaction where molecules break and form new bonds.
Examples include rusting iron, burning wood, and baking a cake. These changes are usually not easy to undo. For instance, you can't turn a rusted nail back into clean iron simply by reversing time.
During a chemical change, observable signs might include color change, temperature change, formation of a precipitate, or gas production.

Observational Skills

Observational skills involve paying attention to the details around you. Good observations are crucial in science because they help us to identify and understand changes involving matter.
To enhance your observational skills, practice noting the small details. Ask yourself questions like: What changes are happening? Is there a new smell or color? Is heat being produced? These questions can guide your observations and help you differentiate between physical and chemical changes.
Taking notes can also be helpful. Write down what you see, and later, reflect on these observations to categorize and analyze them.

Composition of Substances

The composition of a substance refers to what it is made of, including the types of atoms and how they are configured.
In a physical change, the composition of a substance remains the same. For example, liquid water and ice both have the chemical formula H2O.
In contrast, a chemical change alters the composition. For instance, when wood burns, it gets transformed into ash (carbon), carbon dioxide (CO2), and water vapor (H2O). These new substances have different compositions than the original wood.
Understanding composition is vital because it helps identify whether a change is physical or chemical and explains the properties of various materials.