Energy change

Question 1

What is Exothermic

Answer 1

transfer energy from the reacting molecule to the surroundings
so the surroundings get hotter
Products have less energy then the reactant
USERS-hand warmers and self-heating cans

Question 2

What is Endothermic

Answer 2

Take in energy from their surroundings
So temp of surrounding decreases
Product has more energy then reactant

Question 3

What is the difference between activation energy and a catalyst?

Answer 3

ACTIVATION ENERGY
minimum amount of energy that the particles must have for a reaction to take place
CATALYST
reduce the activation energy needed for a reaction. Faster reaction

Question 4

What are the energy change ?

Answer 4

Breaking bonds requires chemical energy=endothermic

Forming bonds, energy given out=exothermic

Question 5

What is the enegy bond calculation??

Answer 5

Exothermic - energy change
Endothermic + energy change
ENERGY CHANGE=BREAK BONDS-FOMRIMG BONDS
reactant-product

Question 6

Cells

Answer 6

2 different metals and place them in an electrolyte=electricity (making a simple cell)
Cells can only produce electricity for a certain period of time, eventually they run out and reaction stops
Cells only produce electricity if we use metals with different reactivity
Greater the difference between the reactivity of the metals greater potential difference (p.d)
electrolyte also affects p.d

Question 7

What is a battery?

Answer 7

Contains 2 or more cells connected in a series to produce a greater voltage

Question 8

What is a fuel cell?

Answer 8

In a hydrogen fuel cell

• Hydrogen and oxygen are supplied to the fuel cell
• Fuel is oxidised to produce P.D
• Overall, hydrogen is oxidised to form water

Question 9

What are the advantage of fuel cell?

Answer 9

Produce water which is non-polluting
Lightweight and small
range of sizes

Question 10

How doo you start the practical?

Answer 10

1) Use a measuring cylinder to measure 30 cm3 of dilute hydrochloric acid
2) Transfer the acid in a polystyrene cup
3) Stand the cup in a beaker so it doesn’t fall

Question 11

When can a reaction occur?

Answer 11

Reactions can only occur when particles collide with each other and they have to do this with sufficient energy

Question 12

What is a non rechargeable battery?

Answer 12

reactant in batteries run out no electricity is produced (EG. alkaline batteries)

Question 13

What is a rechargeable battery?

Answer 13

Can reverse chemical reaction when we apply electrical current

Question 14

What is the half equation for fuel cell?

Answer 14

Hydrogen is at the anode
lose electrons to form hydrogen ions
2H2---4H- + 4e-
Oxygen is at cathode
O2 + 4H+ +4e----2H20
OVERALL,
2H2 + O2--2H20

Question 15

What are the variables?

Answer 15

IV-Volume of sodium hydroxide solution used
DV-Maximum temperature
CV-volume of hydrochloric acid and the conc of both the hydrochloric acid and the sodium hydroxide solution

Question 16

What is the common mistake in the practical?

Answer 16

Keep the bulb end in the thermometer

Question 17

What do you do after placing the acid in the polystyrene cup?

Answer 17

4) Use a thermometer to measure the temp of the acid and record this on a table
5) Now we measure 5cm3 of sodium hydroxide solution and transfer this to the polystyrene cup

Question 18

How do you reduce heat loss?

Answer 18

6) Place a plastic lid (reduces heat loss) on the cup and place the thermometer through the hole in the lid bulb on the thermometer must be in the solution
7) Use the thermometer to stir gently because it is an exothermic reaction it releases energy increasing the tempo

Question 19

What do you do after using the thermometer to stir the acid?

Answer 19

8)Record the highest temp reached then rinse out the cup and repeat the experiment but with 10cm3 of sodium hydroxide solution carry it out several more time and each time increase the volume of sodium hydroxide by 5cm3 until you reach 40cm3

Question 20

What do you do at the end of the practical?

Answer 20

9)Repeat the whole experiment again so you have two sets use this to calculate a mean value.Then plot a graph at some point the graph goes back down because we added so much sodium hydroxide and not enough hydrochloric acid.