Unit 1 Science

Physical Change

A change in physical appearance where no new substances form and the chemical composition remains the same; it's reversible.

Chemical Change

A change that results in the formation of a new substance, is irreversible, and involves rearrangement of particles.

Signs of Chemical Change

Bubbles, temperature change, colour change, sound, gas release, and disappearance of the original substance.

Chemical Synthesis Reaction

When two or more substances combine to form one product, represented as A + B → AB.

Chemical Decomposition Reaction

When a compound breaks down into simpler substances, represented as AB → A + B.

Chemical Reaction Occurrence

Chemical reactions occur when bonds between atoms are broken and new bonds are formed.

Reaction

A rearrangement of atoms.

Reaction Rate

The speed at which a chemical reaction happens.

Collision Theory Principle 1

Particles must collide to react.

Collision Theory Principle 2

Particles must have enough energy to react.

Collision Theory Principle 3

Particles must collide at the correct orientation.

Effect of Concentration on Reaction Rate

Higher concentration leads to faster reaction due to more particles and more collisions.

Effect of Surface Area on Reaction Rate

More surface area leads to faster reaction due to more exposed particles.

Effect of Temperature on Reaction Rate

Higher temperature leads to faster reaction due to more energy and more collisions.

Effect of Agitation on Reaction Rate

More agitation leads to faster reaction by increasing energy and contact among particles.

Catalyst

A substance that accelerates a chemical reaction by lowering activation energy without being consumed in the process.

Exothermic Reaction

A reaction that releases energy, usually in the form of heat or light, resulting in an increase in temperature.

Energy Comparison in Exothermic Reaction

In exothermic reactions, reactants have more energy than products, as energy is released.

Endothermic Reaction

A reaction that absorbs energy from the surroundings, resulting in a decrease in temperature.

Energy Comparison in Endothermic Reaction

In endothermic reactions, products have more energy than reactants, as energy is absorbed.

Law of Conservation of Mass

Mass cannot be created or destroyed in physical or chemical changes.

Combustion

when a substance reacts with oxygen to produce heat and light.

Respiration

how living things release energy from food.