Lets see how the water changes into ice.
Prop: Sponge, water, ice cubes, big silver or painted tumbler.

Magic: You tell your audience that you change water into ice cubes. Now take a tumbler. Pour some water into it. Turn the tumbler upside down. To the wonder, no water is coming out. Instead few ice cubes are falling. How? In no minute, the water is changed into ice cubes.

Secret: Take the tumbler and put some correct fitting sponge into them so that it wont falls out when turned upside down. Now put some ice cubes on it. When you pour water into it, water gets absorbed in the sponge and only ice cubes remain which falls out.