I need help with this question!!

Question 23 (6 points) )Listen My friend is dissolving a powder in the water. After he dissolves the powder, he can no longe tell the difference between the water and the powder. However, no bubbling, temperature change or color change occurred. a) Did my friend make a homogenous mixture or a heterogenous mixture? What is the difference? b) Is dissolving the powder a physical or chemical change? How do you know? c) What are two things he could do to increase the rate of dissolving the powder in water