Chemical Changes And Structure #1: Rates Of Reaction Flashcards

1
Q

Slow reactions

A

Large particles (lumps), low concentration (dilution), low temperature

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2
Q

Fast reactions

A

Small particles (powder), high concentration, high temperature

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3
Q

How do you determine what factor is affecting a chemical reaction?

A

You must only change one variable at a time

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4
Q

What is a variable?

A

Something that can be changed in a chemical reaction

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5
Q

What are some variables?

A
  • temperature
  • particle size
  • concentration
  • volume
  • mass
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6
Q

How do you carry out a fair test?

A

By only changing one variable at a time

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7
Q

What must happen for a chemical reaction to occur?

A

The reactants particles must collide

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8
Q

How do collisions work?

A

The collision provides the energy to break the bonds in the reactant molecules and form the new bonds in the product

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9
Q

Not all collisions result in…

A
  • A chemical reaction
  • Those that do are said to be successful collisions
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10
Q

What makes a successful collision?

A

The particles must collide with:
- the correct geometry (the right angle)
- sufficient energy

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11
Q

Any factor which increases the number of collisions between reactant particles will also increase…

A

The rate of reaction

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12
Q

What is the effect of particle size on collision theory?

A
  • As the particle size decreases, the surface area increases
  • As the surface area increases, the area available for collisions to happen increases
  • This increases the rate of reaction
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13
Q

What is the effect of concentration on collision theory?

A
  • As the concentration of reactants increases, there is more particles and so more collisions
  • Rate of reaction increases
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14
Q

What is the effect of temperature on collision theory?

A

As the temperature increases:
- the amount of energy a particle has increases
- the faster the particle moves around
- the more likely particles are to collide

the rate of reaction increases

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15
Q

All chemical reactions produce…

A

New substances

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16
Q

How can the speed of reaction be measured?

A

By finding how fast the new substance is formed

17
Q

What are 2 ways we can measure the rate of reaction?

A
  • Measuring a change in mass
  • Measuring a change in volume
18
Q

How can we interpret graphs?

A
  • Reactions with more collisions (high conc., high temp., larger surface area / powder) will go to completion/ plateau earlier
  • This is because, in these cases, the reactants are used up quicker because there’s more collisions
19
Q

Labelling parts of a graph

A

A: Reaction rate is fastest. Concentration of reactants is highest.
B: Reaction rate decreases. Concentration decreasing. Reactants being used up.
C: Reaction is finished. All reactants have been converted into products.

20
Q

How do we calculate the average rate of reaction?

A

From knowing the initial and final quantities and the time interval

21
Q

Average Rate formula

A

Average rate = change in quantity / change in time

22
Q

What is a catalyst?

A
  • A substance which speeds up the rate of reaction
  • Can be recovered chemically unchanged
23
Q

What are 4 ways to speed up a chemical reaction?

A
  • Increasing concentration
  • Increasing temperature
  • Increasing particle size
  • Addition of a catalyst
24
Q

Progress of a chemical reaction means

A

Rate of reaction

25
Q

How can the volume of gas produced in a reaction be measured?

A

By using a syringe or upside down measuring cylinder