Name: chemical reaction rates and catalysts
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 22 s
Channel: JoVE

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Chemistry

Matter And Its Interactions

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factors-influencing-the-rate-of-chemical-reactions

Factors Influencing the Rate of Chemical Reactions

For a chemical reaction to proceed, the reactants must collide and overcome the activation energy to break the existing bonds between their atoms and form new products.
Various factors can influence the rate of chemical reactions by increasing the chance of collisions or affecting the activation energy, including reactant concentration and size, temperature, and catalysts.
When the reactants are present in higher concentrations, they collide more frequently, speeding up the reaction.
Further, smaller reactants move faster, collide more frequently, and have a larger surface area to volume ratio, leading to faster reaction rates compared to larger reactants.
At higher temperatures, particles tend to move faster, increasing the chance of collision and product formation, while lower temperatures can slow down the reaction.
Catalysts speed up chemical reactions by lowering the activation energy. In cells, specialized catalysts called enzymes increase the rate of biochemical reactions.
For instance, inside the stomach, the enzyme pepsin breaks down proteins into smaller peptides.

factors influencing the rate of chemical reactions

A variety of factors influence the rate of chemical reactions. For a chemical reaction to happen, atoms must collide with enough energy to overcome the repulsion between their electrons. This energy is called activation energy. Factors influencing the rate of reaction either lower the activation energy or increase the likelihood of a successful collision.
Concentration and Pressure:
The more particles present within a given space, the more likely those particles are to bump into one another. This means that chemists can speed up chemical reactions not only by increasing the concentration of particles&#8212;the number of particles in the space&#8212;but also by decreasing the volume of the space, which would correspondingly increase the pressure.
Temperature: 
The kinetic energy of subatomic particles increases in response to increases in thermal energy. The higher the temperature, the faster the particles move and the more likely they are to come in contact and react. This means that chemical reactions occur at a faster rate at higher temperatures.
Properties of the Reactants:
If chemical reactions are to occur quickly, the atoms in the reactants must have easy access to one another. In general, the greater the surface area of the reactants, the more readily they will interact. Generally, gases tend to react faster than liquids or solids. Energy is required to separate particles of a substance, and gases already have space between their particles. Similarly, the larger the molecule, the greater the number of total bonds, so reactions involving smaller molecules with fewer total bonds would be expected to proceed faster.
A chemical reaction between two or more substances requires intimate contact between the reactants. When reactants are in different physical states or phases (solid, liquid, gaseous, dissolved), the reaction takes place only at the interface between the phases. Consider a heterogeneous reaction between a solid phase and either a liquid or gaseous phase. Compared with the reaction rate for large solid particles, the rate for smaller particles will be greater because the surface area in contact with the other reactant phase is greater. This means that for heterogeneous reactions, the rate of reaction depends on the surface area of the reactant in a more condensed phase.
Enzymes and Catalysts:
A catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any change. A catalyst does this by lowering the activation energy needed to start a chemical reaction. The most important catalysts in the human body are enzymes. Enzymes are critical to the body&#39;s healthy functioning. They assist, for example, with the breakdown of food and its conversion to energy. Most of the chemical reactions in the body are facilitated by enzymes. This means that their deficiency can cause serious health problems. For example, in Tay-Sachs disease, a hexosaminidase enzyme deficiency leads to the accumulation of gangliosides in the brain and spinal cord.
This text is partially adapted from <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/2-3-chemical-reactions?query=rate%20of%20reaction&amp;target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-id2654903">Openstax, Anatomy, and Physiology 2e, Section 2.3: Chemical Reactions</a> and <a href="https://openstax.org/books/chemistry-2e/pages/12-2-factors-affecting-reaction-rates?query=rate%20of%20reactions&amp;target=%7B%22index%22%3A0%2C%22type%22%3A%22search%22%7D#fs-idm103128016">Openstax, Chemistry 2e, Section 12.2 </a><a href="https://openstax.org/books/chemistry-2e/pages/12-2-factors-affecting-reaction-rates?query=rate%20of%20reactions&amp;target=%7B%22index%22%3A0%2C%22type%22%3A%22search%22%7D#fs-idm103128016">Factors Affecting Reaction Rates</a>

A variety of factors influence the rate of chemical reactions. For a chemical reaction to happen, atoms must collide with enough energy to overcome the ...

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Anatomy and Physiology

Unit 1

Fundamentals of Chemistry

KEY TERMS AND CONCEPTS

chemical reaction rates and catalysts

Chemical reaction rates depend on how often particles collide and whether those collisions have enough energy to start a reaction. That starting energy is called activation energy. Factors that affect reaction rate either lower that energy or make successful collisions more likely.

Concentration and pressure can speed reactions up because they put more particles in the same space. When more particles are present, they are more likely to bump into one another. Chemists can also increase pressure by decreasing volume, which raises the chance of collision.

Temperature also affects reaction rate. As thermal energy increases, particle motion increases too. Faster-moving particles are more likely to meet and react, so reactions usually happen more quickly at higher temperatures.

The properties of the reactants matter as well. Reactions happen faster when atoms have easy access to one another, so greater surface area usually means a faster rate. In many cases, gases react faster than liquids or solids, and smaller molecules often react faster than larger ones because they have fewer total bonds.

When reactants are in different phases, such as a solid with a liquid or gas, the reaction happens only where the phases touch. For a solid reactant, smaller particles give more surface area in contact with the other substance, so the reaction rate is greater than with large solid pieces. Catalysts also increase reaction rate by lowering activation energy, and enzymes are the most important catalysts in the human body. Enzymes help break down food and convert it to energy, and many body reactions depend on them. A lack of one enzyme can cause serious health problems, such as Tay-Sachs disease, where hexosaminidase deficiency leads to ganglioside buildup in the brain and spinal cord.

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Chemical reaction rates depend on how often particles collide and whether those collisions have enough energy to start a reaction. That starting energy is called activation energy. Factors that affect reaction rate either lower that energy or make successful collisions more likely. Concentration and pressure can speed reactions up because they put more particles in the same space. When more particles are present, they are more likely to bump into one another. Chemists can also increase...

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Chemical Reaction Rates and Catalysts

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