Chemical Reactions Flashcards
(26 cards)
What is a chemical formula?
A way of showing which elements are in a compound and how many atoms of each.
What do the small numbers in a formula mean?
They show how many atoms of that element are present.
Why are metals good conductors of electricity?
Because they have free-moving electrons.
What does ductile mean?
Ductile means they can be drawn into wires.
Do metals have high or low melting and boiling points?
High melting and boiling points, with a few exceptions like mercury.
Which metals are magnetic?
Mainly iron, cobalt and nickel.
How do metals react with acids?
Many metals react with acids to produce a salt and hydrogen gas.
Do metals lose or gain electrons in reactions?
Metals lose electrons and form positive ions in reactions.
What is the reactivity series:
A list of metals (and carbon/hydrogen) in order of how easily they react, especially with water, acids and oxygen.
Which metal is the most reactive in the reactivity series?
Potassium (K).
Which metal is the least reactive from the common metals?
Gold (Au) – it doesn’t react easily at all which is why it is the most suitable metal to be used for jewellery.
How does the reactivity of a metal relate to its reaction with acids?
More reactive metals fix/bubble more with acids, producing hydrogen gas faster.
What happens when a more reactive metal is placed in a salt solution of a less reactive metal?
A displacement reaction occurs – the more reactive metal pushes the less reactive one out.
What happens when magnesium is added to copper sulfate solution?
Magnesium displaces copper – magnesium sulfate forms and copper is left as a solid.
How is the reactivity series useful for extracting metals from ores?
Metals less reactive than carbon can be extracted by reduction with carbon. More reactive metals need electrolysis.
What is the law of conservation of mass?
Mass is never lost or gained in a chemical reaction – the total mass of the reactants equals the total mass of the products.
Why is mass conserved in a chemical reaction?
Because atoms are rearranged, not created or destroyed.
What would you observe if the mass seems to decrease during a reaction?
A gas may have escaped into the air (e.g carbon dioxide.)
What would you observe if the mass seems to increase during a reaction?
A gas from the air (like oxygen) may have been taken in.
How do you balance equations?
- Counts the atoms on each side.
- Balance the atoms for 1 element.
- Balance the atoms for the remaining elements.
What does it mean when a chemical equation is balanced?
The number of atoms of each element is the same on both sides – mass is conserved.
What is combustion?
A chemical reaction where a substances reacts with oxygen, releasing energy (usually heat and light.)
What is an exothermic reaction?
A reaction that releases energy to the surroundings – the temperature goes up.
What is an endothermic reaction?
A reaction that absorbs the energy from the surroundings – the temperature goes down.
