Science Semester 2 - Changing Matter

Solids are a state of matter that have a fixed shape and volume. The particles in a solid are closely packed together and have strong intermolecular forces, which prevent them from moving freely. This arrangement gives solids their definite shape and volume, as the particles are unable to flow or take the shape of their container.

Liquids have a fixed volume, meaning they do not compress or expand, but their shape can change depending on the container they are in. Unlike solids, which have a fixed shape, liquids can take the shape of their container, making them adaptable and able to flow. This is why liquids are often found in containers and can be poured or transferred easily.

Gas is a state of matter that has no fixed shape or volume. Unlike solids and liquids, gases are able to fill the space they occupy completely, taking on the shape of their container. Gas particles are in constant random motion and have weak intermolecular forces, allowing them to move freely and spread out to fill any available space. This makes gas a highly compressible state of matter, as its volume can be easily changed by altering the pressure or temperature.

When ice is added to hot water, it slowly melts. The heat from the hot water causes the ice to absorb energy, which increases the temperature of the ice. As a result, the ice changes from a solid state to a liquid state, turning into water. The process of melting is gradual, as the heat is transferred to the ice molecules, causing them to break their bonds and transition into a liquid form. Thus, the ice slowly melts when added to hot water.

Physical changes occur when a substance receives or loses energy, specifically heat. This is because heat is a form of energy that can cause the particles in a substance to move faster or slower, leading to changes in its physical state or properties. When a substance gains energy, its particles gain kinetic energy and move faster, resulting in a change such as melting or boiling. Conversely, when a substance loses energy, its particles lose kinetic energy and move slower, leading to changes like freezing or condensation. Therefore, energy, particularly in the form of heat, is essential for physical changes to occur in substances.

The three states of matter are gas, liquid, and solid. Gas is the lightest state of matter as its particles are not closely packed and have high energy. Liquid is the intermediate state of matter where the particles are closer together but still able to move around. Solid is the heaviest state of matter as its particles are tightly packed and have low energy, resulting in a fixed shape and volume.

Evaporation is the process by which water is heated and transforms into steam. When heat is applied to water, the water molecules gain energy and start moving faster. This increased kinetic energy allows some of the water molecules to escape from the liquid phase and enter the gas phase, forming steam. Evaporation is a natural process that occurs at any temperature, but it is accelerated when heat is applied.

The process of returning melted ice to its original state involves cooling or freezing the ice. When ice melts, it changes from a solid to a liquid state. By cooling or freezing the liquid, it can be converted back into its original solid state as ice.

Fizzing tablets contain ingredients that react with water to release carbon dioxide gas. This gas forms bubbles in the water, creating a fizzy or effervescent effect. Therefore, when fizzing tablets are added to water, bubbles are created.

When salt is added to water, it dissolves.

The statement "Melted chocolate is irreversible" is false. When chocolate is melted, it undergoes a physical change from a solid to a liquid state. This change is reversible, as the melted chocolate can be cooled and solidified again by reducing its temperature. Therefore, melted chocolate can be reversed back to its original solid form.

A candle requires three things to burn: heat, fuel, and oxygen. Oxygen is necessary for the combustion process to occur. When the heat from the flame reaches the fuel (wax or wick), it vaporizes and reacts with the oxygen in the air, producing heat, light, and carbon dioxide. Without oxygen, the candle would not be able to sustain its flame and continue burning. Therefore, the third thing needed for a candle to burn is oxygen or air.