Write C for chemical change and P for physical change. Give evidence to support your answer.
A rusting bicycle
spoiling food
burning paper
frying an egg
baking a cake
melting butter
A rusting bicycle: C - This is a chemical change because the iron in the bicycle reacts with oxygen in the presence of water and forms rust (iron oxide).
Spoiling food: C - Spoiling food involves chemical changes caused by the growth of bacteria, yeasts, or molds that break down the organic matter in the food.
Burning paper: C - Burning paper involves a chemical change where the paper undergoes combustion. It reacts with oxygen, releases heat and light, and forms carbon dioxide and water vapor.
Frying an egg: C - Frying an egg is a chemical change as the proteins in the egg white denature and coagulate when exposed to heat, resulting in a solid structure.
Baking a cake: C - Baking a cake involves various chemical reactions. The ingredients undergo chemical changes due to heat, such as the leavening agents reacting with the acid and moisture to produce carbon dioxide and make the cake rise.
Melting butter: P - Melting butter is a physical change as it changes from a solid to a liquid state due to the increase in temperature. The chemical composition of the butter remains the same.
What do you think the difference is between a physical and chemical change? Be specific with your answer!
The main difference between a physical change and a chemical change is the nature of the changes that occur to the substances involved.
In a physical change, the substance undergoing the change remains the same chemically. The physical properties of the substance, such as its shape, size, phase (solid, liquid, gas), and density, may change, but the chemical composition of the substance remains intact. Physical changes are typically reversible, meaning the substance can be changed back to its original state without undergoing any chemical reactions.
In contrast, a chemical change involves the rearrangement of atoms or molecules in a substance, resulting in the formation of new substances with different chemical properties. During a chemical change, the molecular or atomic composition of the substance is altered, and new chemical bonds are formed or broken. Chemical changes are usually accompanied by the absorption or release of energy in the form of heat, light, or sound.
It is important to note that physical changes do not alter the chemical identity of a substance, while chemical changes result in the formation of different substances with different chemical identities.
A rusting bicycle: C (Chemical Change)
Evidence: Rusting involves a chemical reaction between iron and oxygen in the presence of water or moisture. This reaction forms iron oxide, commonly known as rust. The new substance formed (rust) has different physical and chemical properties from the original iron.
Spoiling food: C (Chemical Change)
Evidence: Spoiling food involves microbial activity, such as the growth of bacteria or fungi on the food. These microorganisms produce enzymes and release waste products that break down the molecular structure of the food, altering its taste, texture, and smell. The changes in the food are a result of chemical reactions occurring within the food.
Burning paper: C (Chemical Change)
Evidence: Burning paper involves a combustion reaction, where the paper undergoes a chemical reaction with the oxygen in the air. This reaction releases heat and light energy and results in the formation of new substances, such as carbon dioxide, water vapor, and ash. The ash is a residue left behind after the paper undergoes a chemical change.
Frying an egg: C (Chemical Change)
Evidence: Frying an egg involves the application of heat, which causes several chemical changes to occur. The proteins in the egg undergo denaturation, changing their structure and properties. Additionally, the heat causes chemical reactions to take place, leading to the coagulation of proteins and the release of new aroma compounds.
Baking a cake: C (Chemical Change)
Evidence: Baking a cake involves a complex series of chemical reactions. The heat causes the leavening agents (like baking powder or baking soda) to release carbon dioxide gas, which gets trapped in the batter, causing it to rise. The proteins in the flour coagulate, starches gelatinize, and sugars caramelize, leading to the formation of a solid, fluffy, and flavorful cake.
Melting butter: P (Physical Change)
Evidence: Melting butter is a physical change because it involves a change in the state of matter from a solid to a liquid. When butter is heated, its molecular structure changes, and the cohesive forces holding the solid butter together are overcome, resulting in the formation of a liquid. The chemical composition of butter remains the same before and after melting.
- Rusting bicycle: C (Chemical Change)
Evidence: Rusting is a chemical reaction involving the combination of iron, oxygen, and water to form iron oxide (rust). The color of the metal changes, and it cannot be reversed by physical means. It also involves the formation of new substances.
- Spoiling food: C (Chemical Change)
Evidence: When food spoils, it undergoes decomposition through the activity of microorganisms or chemical reactions. The appearance, taste, and smell of the food change as new compounds are formed. The changes are irreversible and involve the breakdown of complex molecules.
- Burning paper: C (Chemical Change)
Evidence: Burning paper involves a chemical reaction called combustion, where the cellulose in the paper reacts with oxygen to produce carbon dioxide, water vapor, and ash. The paper is transformed into new substances, and the process is usually accompanied by the release of heat and light.
- Frying an egg: C (Chemical Change)
Evidence: Frying an egg is a chemical change because heat causes the proteins in the egg white and yolk to denature and form new compounds. As the heat is applied, the liquid egg solidifies and changes color, texture, and taste, making it a chemical transformation that cannot be easily reversed.
- Baking a cake: C (Chemical Change)
Evidence: Baking a cake involves several chemical reactions. The ingredients, such as flour, sugar, eggs, and leavening agents, undergo chemical changes when exposed to heat. These changes include protein denaturation, caramelization, and Maillard reactions which transform the cake batter into a solid and flavorful cake.
- Melting butter: P (Physical Change)
Evidence: Melting butter is a physical change because it only involves a change in the state of matter - from a solid to a liquid - due to the application of heat. The chemical composition of butter remains the same, and the change can be reversed by cooling the melted butter.