1K Chemical Changes
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What is formed in a chemical reaction?
A new substance
What is a physical change?
In a physical change, no new susbtance is formed and it is easy to reverse.
What are the signs of a chemical reaction?
• Energy Change (normally temperature change) • Colour Change • Effervescence (bubbles of gas given off) • Precipitate (solid) formed
Give an example of a physical change/
A change of state like ice melting to water.
What is conservation of matter?
Matter cannot be created or destroyed during a chemical reaction.
What is the link between atoms on the right of an equation and atoms on the left?
The number of atoms on the left of the arrow (reactants) is always equal to the number on the right of the arrow (products)
Why do we balance chemical equations?
The number of atoms of each type of element must be the same on each side of the equation.
What does rate of reaction mean?
How slowly or quickly the reaction takes to happen.
How could you measure the rate of a reaction>
We could count the number of bubbles produced over a period of time. We could measure the volume of gas produced over a period of time. We could let the gas escape and measure the mass lost after a set period of time.
What does a rate graph tell us about a reaction?
The steeper the curve the faster the reaction.
What has to happen for a reaction to take place/
The particles must collide. The faster they collide the faster the reaction.
How can increasing temperature increase the rate of a reaction?
A higher temperature = more energy so reactant particles collide more.
How can increasing concetration increase the rate of a reaction?
The higher the concentration of a solution the faster the reaction. The higher the concentration of a solution the more particles there are so the better the chance of particles colliding, so speeding up the reaction.
How can changing particle size increase the rate of a reaction.
By decreasing the particle size of a reactant, there are more surfaces that collisions can take place on. The smaller the particle sizes the faster the reaction.
What is a catalyst?
A catalyst is a chemical that speeds up a chemical reaction but is chemically unchanged at the end of reaction.
How does a catalyst work?
Catalysts speed up reactions by giving the reactants a surface on which to react. A catalyst may work for various chemical reactions.
What is an enzyme?
Enzymes are similar to catalysts in that they also speed up chemical reactions and do not get used up during the reaction. They are very specific - one enzyme will only speed up one particular type of chemical reaction.
What is neutralisation?
When an acid and a base neutralise each other and form a salt and water.