Thursday, May 17, 2012

Science Module 9 Assignment 3 - 3rd year

1. When making ice cream using a manual ice-cream freezer, why do you put salt on ice?
The salt mixed with ice helps to make the right substance for the ice cream. You can do this with an ice cream maker or you can also do this with Glad Zip lock bags. Get a small size bag and a gallon size bag. Put a lot of salt and ice in the gallon size bag. In the smaller size bag put a cup of milk, a half to a cup of sugar, and teaspoon of vanilla. Zip the small bag up tightly then put it in the gallon size bag. Then zip the gallon size bag. And knead it over and over. About 15 - 20 min. And soon you will have ice cream.

2. Why salty soil kills plants?
The roots of a plant take in water from the soil by way of "osmosis", where water moves through a semi-permeable membrane. Water molecules can pass through, but not larger (dissolved) molecules. But since water actually flows both in and out, in both directions, the plant needs a surplus moving to the inside. High concentrations of dissolved substances in the ground water (solutes) tend to block the inward flow and prevent the plant from absorbing enough water to sustain its life processes.

3. Why we must drink fresh water and not seawater?
Humans can't drink salt water because the kidneys can only make urine that is less salty than salt water. Therefore, to get rid of all the excess salt taken in by drinking salt water, you have to urinate more water than you drank, so you die of dehydration.

No comments:

Post a Comment