Question

The fumes from gasoline are more likely than liquid gasoline to catch fire when in contact with static electricity. Explain using collision theory.

Short answer

Gasoline fumes are more likely to catch fire when in contact with static electricity, because since the particles in the fumes are well-dispersed, they collide more frequently and more likely to catch fire compared to liquid gasoline in which particles are closely packed and have less freedom of movement. This explanation is based on Collision theory that necessitates particles to collide, with enough energy and correct orientation, for a reaction, in this case, combustion to occur.

Step-by-step solution

Understanding Collision Theory

Collision theory states that for a chemical reaction to occur, the reactant particles must collide. These collisions must have sufficient energy and the correct orientation. The number of successful collisions with enough energy to break the existing bonds and form new bonds will determine the rate of the reaction.

Differentiation between Liquid and Gaseous State

In the gaseous state, particulate matter is extensively dispersed, having more space between individual molecules allowing them greater freedom of movement. On the other hand, in the liquid state, particles are much closer together, resulting in lesser freedom of movements. This difference in the state of matter changes the likelihood of successful collisions.

Application of Collision Theory to Gasoline Fumes

When gasoline evaporates into fumes, its particles disperse. This dispersion increases the likelihood of a flammable mix of gasoline vapor and air. When static electricity is introduced, it provides the necessary activation energy to initiate combustion. Since the particles in the vapor phase are spread out, there is a higher chance of collision with enough energy to initiate a reaction, hence are more susceptible to catch fire than liquid gasoline.

Key concepts

gasoline fumes

Gasoline fumes are the gaseous form of gasoline, which is usually a highly volatile liquid fuel. When gasoline evaporates, it turns into fumes, mixing with the air around. This transformation into gas allows the particles to spread more widely and freely.
Unlike liquid gasoline, these fumes have a significant potential to ignite. When particles are in the gaseous state, they can move around more and encounter oxygen molecules more easily. This higher mobility means an increased chance for collisions.
In an environment filled with gasoline fumes, even a tiny spark can trigger a fire. This is because the fumes have already mixed with air, forming a ready-to-burn mixture. That's why handling gasoline requires careful attention to prevent any potential fire hazards.

static electricity

Static electricity refers to the electric charge that builds up on the surface of materials. Static charges form when certain materials rub together, causing a transfer and imbalance of electrons.
When something like your clothes or hair sticks to you with an electric zap, that's static electricity in action. In everyday life, static can simply be a minor inconvenience. However, when combined with gasoline fumes, it can lead to dangerous situations.
In environments where evaporated gasoline exists, the presence of static electricity is concerning. Even a small discharge of static can spark and provide the energy necessary for a fire to ignite, especially when it directly touches a fume cloud. The energy from static electricity acts as an ignition source.

reaction rate

The reaction rate is the speed at which a chemical reaction occurs. It is determined by how frequently reacting particles collide with each other and whether those collisions have sufficient energy to lead to a new product.
Chemical reactions require an energy threshold known as activation energy. For reactions to proceed quickly, many collisions between molecules must happen with energy surpassing this threshold.
In the case of gasoline fumes, the reaction rate with static electricity is considerable. This is because the fumes mix well with oxygen in the air, and any spark or heat source can provide the essential activation energy, bringing about a rapid reaction — combustion. Therefore, a little spark is enough to catalyze a quick and potentially explosive reaction.

state of matter

The state of matter refers to the distinct forms that different phases of matter assume. The most familiar states are solid, liquid, and gas.
In solids, particles are tightly packed, giving them a definite shape and limited freedom to move. In liquids, particles are closer together than gases but can slide past each other, so liquids take the shape of their containers. Gases have particles spread far apart, moving freely, and can fill any container they enter.
These states influence how substances react. Gasoline, when in its liquid state, is less prone to catch fire compared to its gaseous state. In gas form, the widespread dispersion of gasoline particles leads to easier mixing with air, increasing the chance of collisions and reactions like combustion. This exemplifies why handling gases requires extra caution compared to liquids or solids.