A student is given 10g of three different powders, M, N and P. He adds each powder to separate beakers containing 30cm3 of water and stirs five times. Here are his results
A.some of the powder dissolves
B.all of the powder dissolves
C.none of the powder dissolves
Which can power can be completely separated from the water by using only filttration
A.M
B.N
C.P
D.None of the powders
Chọn D - None of the powders
Tạm hiểu câu hỏi là có bạn học sinh hòa tan mấy gam bột khác loại vào nước, có cái tan/ không tan/ tan 1 phần thì hỏi có thể tách bột và nước ra riêng mà chỉ dùng phương pháp lọc được không?.
Thì câu trả lời là không (hiểu đơn giản thì khi bột hòa tan vào nước, các hạt bột sẽ phân tán đều trong dung dịch nước, nó nhỏ hơn kích thước lỗ lọc của bất kỳ bộ lọc nào nên không lọc được)
Drying is the oldest type of food preservation. If water is (1) ________ from food, the bacteria can't grow. In (2) ________ times in hot countries, people simply left fruit and meat outside to dry in the sun and the wind until all its natural water was gone. This make the fruit last a very long time. Drying fruit sometimes results in a completely new (3) ________ . For example, grapes turn into raisins and plums turn into prunes. Drying food in the sun does not work in cooler or wetter climates, but people have other (4) ________ to preserve feed in cold places. 2. Salting: Salting food, especially meat and fish, is another very old way to preserve food. Bacteria cannot grow in a very salty environment, so salted food lasts a long time. In many countries, salt fish or meat has become a (5) ________ food and people still eat it today. For example, in Portugal the national dish is salt cod fish, and although people could buy fresh fish and (6) ________ it, they prefer to eat the preserved fish.