rust cleaning

last august 26, we had our rust cleaning in front of our room. it's because of the experiment we made last week. and the salt is scattered all over the stair's metals that made them rust. the salt has its own contents which made the metal exposed to air. so before it damages the metal, we need to repaint the metal so that the whole will be covered and it will not anymore be exposed to air.

thermal energy of ice cream(august 20)

maTeriALs:

• 2 cups evaporated milk
• 4 tablespoons of brown sugar
• chocolate powder (any flavor of your choice)
• container
• 1 kilo of rock salt
• crashed ice (7 pcs-depends on the size of the container)
• can/

sTePs:

• mix the ingredients (evaporated milk, brown sugar, chocolate powder) in the can/;
• prepare the container, then put the ice and cover the outer part of the crashed ice with 1/4 kilo of rock salt;
• place the can (with cover) with ice cream mixture inside the large container;
• after the placing the can, put the ice and rock salt over the can alternatively until it reaches the cover or until the container is full;
• Shake the container until the harden ice cream is made.

Questions:

• Why did we put a salt on the ice?

answer: because salt prevents the ice from melting and "we add salt to lower the freezing point of water, from 0 degrees celsius to lower than zero. When the freezing point of water decreases, its melting point also lowers thus, the ice actually melted but the temperature is much lower than zero. Such low temperature makes the ice cream mixture to solidify.."(ma'am rhea)

• Is melting exothermic or endothemic?how about freezing?

answer: Melting is endothermic because heat is absord from the surrounding to the system.

While, freezing is exothermic because heat is released from the system to the surrounding.