Chemistry-wjec Gcse

PVC, short for polyvinyl chloride, is commonly used for window frames due to its durability and weather resistance properties.

Polyethylene is a versatile plastic known for its light weight, flexibility, and resistance to moisture. It is commonly used for making plastic bags due to its durability and affordability.

PTFE is a synthetic polymer that is known for its non-stick properties, making it ideal for use in cookware such as frying pans.

A saturated compound refers to a compound that has no double or triple bonds, meaning that all available bonds are single bonds.

Metals have high melting and boiling points because of the strong metallic bonding between the positive cations and the delocalized electrons, leading to a high level of bond strength.

Simple molecular substances have weak intermolecular forces, resulting in low melting and boiling points. Strong intermolecular forces are necessary for higher boiling and melting points.

Simple molecular substances have low melting and boiling points because the intermolecular forces of attraction between molecules are weak. These weak forces require less energy to break, resulting in lower melting and boiling points compared to substances with stronger intermolecular forces.

Giant ionic crystals have high melting and boiling points because of the strong forces of attraction between oppositely charged ions. Weak intermolecular forces, low atomic masses, and high kinetic energy do not contribute to the high melting and boiling points of giant ionic crystals.

Giant covalent structures have high melting points because they possess a vast number of covalent bonds extending in all directions, requiring significant energy to break these bonds during melting.

Polymer gels, like hydrogels, are known for their ability to absorb and expel large amounts of water, leading to swelling or shrinking based on conditions.

Shape memory polymers have the unique ability to return to their original shape when they are heated, making them ideal for applications where their shape can be manipulated temporarily.

Polymer gels are commonly used in nappies for absorption and in artificial muscles for actuation.

Shape memory polymers are often used in the automotive industry due to their ability to return to their original shape after being deformed. This property is particularly useful in car bodies where impact resistance and shape retention are crucial.

Photochromic paints change color when exposed to light, making them a popular choice for products such as color-changing clothing, sunglasses, and mood rings.

Thermochromic paints change color based on temperature, unlike options glowing in the dark, conducting electricity, or changing size.

Polymer gels are the smart materials used in 'magic snow' as they have the ability to absorb large amounts of water and expand just like real snow. Silicone rubber, shape memory alloys, and piezoelectric materials do not possess the same characteristics as polymer gels when it comes to mimicking snow.

Polymer gels have a cross-linked polymer structure that allows them to hold a large amount of solvent within their network, leading to swelling or shrinking behavior.

The correct answer addresses the main concern of uncertainty related to the long-term impact on health due to the use of smart materials in medicine-releasing implants.

Shape memory alloys are metallic materials that have the ability to return to a predetermined shape or size when subjected to an appropriate thermal stimulus. This unique property allows them to retain their shape even after being deformed.

Shape memory alloys are commonly used in spectacle frames due to their unique ability to retain their shape after being deformed. They are not typically used for building construction materials, automobile tires, or food packaging.

To effectively crack hydrocarbons, the two essential conditions are heat and a catalyst. Heat provides the energy needed to break the carbon-carbon bonds in the hydrocarbon molecules, while a catalyst helps facilitate the reaction without being consumed in the process.

Ionic bonding occurs between a metal and a non-metal where one atom donates an electron to another, resulting in the formation of ions with opposite charges that are held together by electrostatic forces.

Covalent bonds are formed between non-metal atoms by sharing electrons. Metals typically form ionic bonds with non-metals, while noble gases are inert and do not readily form bonds.

In metallic bonding, the atoms within a metal element share a sea of electrons, allowing for strong bonds between the metal atoms. This type of bonding is unique to metals and does not occur between a metal and a non-metal or two non-metals.

Ionic bonding involves the transfer of electrons from one atom to another, resulting in the formation of ions with opposite charges that are then attracted to each other to form a bond.

Alkanes are primarily used in the production of fuels due to their flammable nature and ability to combust for energy. The other options do not align with the typical uses of alkanes.

Alkanes are saturated hydrocarbons, meaning they only have single bonds between the carbon atoms, resulting in each carbon being bonded to the maximum number of hydrogen atoms possible.

Propane is a hydrocarbon compound with the formula C3H8, consisting of three carbon atoms and eight hydrogen atoms. The other options provided are the chemical formulas for carbon dioxide (CO2), water (H2O), and sodium chloride (NaCl) which are different compounds altogether.