Priya and Lily are investigating the energy changes that take place during dissolving.

They follow this method:

• Pour $10{\mathrm{cm}}^3$of water into a boiling tube.

• Record the temperature of the water. Add $0.5\mathrm{g}$of ammonium chloride and stir.

• Record the temperature when the ammonium chloride has dissolved.

Here are their results: 
Start temperature in °C $20.0$
The final temperature in  $°\mathrm{C}$$18.5$

Priya thinks that if they repeat the experiment using $9{\mathrm{cm}}^3$water the temperature change will stay the same, but Lily thinks it will decrease further. 

Explain why Lily is correct.

The word equation for photosynthesis is:

water + carbon dioxide $\to$glucose + oxygen

The word equation for respiration is:

glucose + oxygen $\to$carbon dioxide + water

Use your scientific knowledge to explain which process is exothermic and which is endothermic.

Match each change of state with its energy change. 

Change of state: Melting, freezing, condensing, evaporating

Energy change: Exothermic, Endothermic.

Explain how sweating cools the skin. 

Energy transfers from the skin to sweat as ______. A moisture leaves the skin _____ , it carries a lot of heat with it, cooling your body.

The diagram shows a burring candle.

Describe what happens to the wax as the candle burns. 

Safi has drawn a sketch graph to show how the temperature of the wax changes as the candle burns. Explain why there is a plateau in the graph.