Chemical Reactions/ Equations

Question 1

Evidence of a chemical change? (4)

Answer 1

• substance disappears
• gas is given off
• precipitate occurs
• colour change takes place
• temperature change
• new odour released
• light is given out

Question 2

What is the difference between chemical change and physical change?

Answer 2

A chemical change is a reaction where a substance is transformed into a new one where as a physical change only results in the substance shanking state. It’s reactants can be re-obtained.

Question 3

What are the similarities between chemical change and physical change? (2)

Answer 3

• result in a visual change

- result in energy loss or gain

Question 4

What is a precipitation reaction?

Answer 4

A reaction where ions combine to form a her produvt of low solubility called a precipitate.

Question 5

What is an acid base reaction?

Answer 5

When an acid reacts with a base and there is a transfer of a proton. Also called a neutralisation reaction.

Question 6

What are the acid- base reactions?

Answer 6

1. Acid + metal = salt + hydrogen
2. Acid + metalcarbonate = salt + h2o +CO2
3. Acid + metal oxide = salt + water
4. Acid + metal hydroxide = salt + water

Question 7

What is a combustion reaction?

Answer 7

When a hydrocarbon is burned in a plentiful supply of oxygen which results in the products CO2 and water.

Question 8

What is the formula for a combustion reaction?

Answer 8

CxHy + (x+ y/4)O2 = xCO2 + (y/2)H2O